What are the normal AST ranges. How do high and low AST levels affect health. What causes abnormal AST results. What symptoms are associated with AST abnormalities. How is AST testing used to diagnose liver conditions.

What is AST and Why is it Important?

Aspartate aminotransferase (AST) is an enzyme found in various tissues throughout the body, including the liver, heart, muscles, and kidneys. It plays a crucial role in amino acid metabolism and is often used as a biomarker to assess liver health and function. When cells containing AST are damaged, the enzyme is released into the bloodstream, causing elevated levels that can be detected through blood tests.

AST testing is an essential component of liver function panels and is frequently used in conjunction with other tests to diagnose and monitor liver conditions. Understanding AST ranges and their implications is vital for both healthcare providers and patients in assessing overall health and detecting potential liver issues.

Normal AST Ranges: What Do They Mean?

Normal AST ranges can vary slightly depending on the laboratory and testing method used. However, typical reference ranges for adults are as follows:

• Men: 10 to 40 units per liter (U/L)
• Women: 9 to 32 units per liter (U/L)

It’s important to note that these ranges are based on population studies and may not necessarily reflect optimal health for all individuals. Some experts suggest using lower upper limits of normal (ULN) to better identify potential liver issues:

• Men: 30 U/L
• Women: 19 U/L

AST levels within these ranges generally indicate that the liver and other organs are functioning normally. However, it’s crucial to interpret AST results in conjunction with other liver enzymes and clinical findings for a comprehensive assessment of liver health.

High AST Levels: Causes and Implications

Elevated AST levels can be indicative of various conditions affecting the liver and other organs. Some common causes of high AST include:

1. Acute hepatitis (viral, alcoholic, or drug-induced)
2. Chronic liver diseases (cirrhosis, nonalcoholic fatty liver disease)
3. Liver cancer
4. Muscle disorders or injuries
5. Heart conditions (myocardial infarction, heart failure)
6. Severe burns
7. Pancreatitis
8. Certain medications

The degree of AST elevation can provide clues about the underlying condition. Mild elevations (less than 5 times the ULN) are often seen in chronic liver diseases, while more significant elevations (greater than 15 times the ULN) may indicate acute liver injury or severe muscle damage.

Interpreting AST/ALT Ratio

The ratio of AST to alanine aminotransferase (ALT), another liver enzyme, can offer additional insights:

• AST/ALT ratio < 1: Typically seen in viral hepatitis and nonalcoholic fatty liver disease
• AST/ALT ratio > 2: Often associated with alcoholic liver disease or advanced liver fibrosis

This ratio, known as the De Ritis ratio, can help differentiate between various liver conditions and guide further diagnostic workup.

Low AST Levels: Are They a Concern?

While high AST levels often indicate potential health issues, low AST levels are generally not a cause for concern. AST levels below the reference range are rarely clinically significant and do not typically require further investigation unless accompanied by other abnormal test results or symptoms.

In some cases, very low AST levels may be seen in individuals with vitamin B6 deficiency, as this vitamin is a cofactor for AST activity. However, this finding alone is not diagnostic and would require additional testing to confirm.

Symptoms Associated with Abnormal AST Levels

AST levels themselves do not cause symptoms. However, the underlying conditions causing elevated AST may present with various signs and symptoms, including:

• Fatigue
• Jaundice (yellowing of skin and eyes)
• Abdominal pain or discomfort
• Nausea and vomiting
• Loss of appetite
• Dark urine
• Pale stools
• Itching
• Muscle pain or weakness (in cases of muscle-related AST elevation)

It’s important to note that many liver conditions can be asymptomatic in their early stages, which is why routine liver function tests, including AST, are crucial for early detection and management of liver diseases.

Diagnosing Liver Conditions Using AST and Other Liver Function Tests

AST is typically measured as part of a comprehensive liver function panel, which includes other enzymes and proteins such as:

• Alanine aminotransferase (ALT)
• Alkaline phosphatase (ALP)
• Gamma-glutamyl transferase (GGT)
• Bilirubin
• Albumin
• Prothrombin time

The pattern of elevation in these markers can help differentiate between various liver conditions:

Hepatocellular Injury Pattern

In hepatocellular injury, which affects liver cells directly, AST and ALT are typically elevated more than ALP and GGT. This pattern is seen in conditions such as viral hepatitis, drug-induced liver injury, and nonalcoholic fatty liver disease.

Cholestatic Pattern

Cholestatic liver diseases, which affect bile flow, usually present with more significant elevations in ALP and GGT compared to AST and ALT. Examples include primary biliary cholangitis and biliary obstruction.

Mixed Pattern

Some conditions may show a mixed pattern of elevation, with increases in both hepatocellular and cholestatic enzymes. This can be seen in certain drug-induced liver injuries and autoimmune liver diseases.

When interpreting liver function tests, it’s crucial to consider the patient’s clinical presentation, medical history, and other relevant factors to arrive at an accurate diagnosis.

Factors Affecting AST Levels and Test Results

Several factors can influence AST levels and potentially lead to false-positive or false-negative results:

1. Medications: Certain drugs, such as acetaminophen, statins, and some antibiotics, can affect AST levels.
2. Alcohol consumption: Recent alcohol intake can temporarily elevate AST levels.
3. Exercise: Intense physical activity, especially if unaccustomed, can cause transient AST elevations due to muscle breakdown.
4. Hemolysis: Breakdown of red blood cells during blood collection or processing can falsely elevate AST levels.
5. Pregnancy: AST levels may be slightly lower during pregnancy.
6. Body mass index (BMI): Obesity is associated with higher baseline AST levels.
7. Age and gender: Reference ranges may vary based on these factors.

Healthcare providers should consider these factors when interpreting AST results and may recommend repeat testing or additional investigations if results are inconsistent with clinical findings.

Management and Treatment of Abnormal AST Levels

The management of abnormal AST levels primarily focuses on addressing the underlying cause. Treatment approaches may include:

• Lifestyle modifications: Reducing alcohol intake, maintaining a healthy diet, and increasing physical activity can help improve liver health in many cases.
• Medication adjustments: If drug-induced liver injury is suspected, the offending medication may need to be discontinued or replaced.
• Antiviral therapy: For viral hepatitis, specific antiviral medications may be prescribed.
• Immunosuppressive therapy: In cases of autoimmune liver diseases, immunosuppressants may be used to control inflammation.
• Treatment of underlying conditions: Managing heart disease, muscle disorders, or other non-liver conditions causing AST elevation.
• Liver transplantation: In cases of end-stage liver disease, transplantation may be considered as a last resort.

Regular monitoring of AST levels, along with other liver function tests, is crucial for assessing treatment efficacy and disease progression. The frequency of follow-up testing depends on the severity of the condition and the chosen treatment approach.

Lifestyle Recommendations for Liver Health

Regardless of the specific cause of AST elevation, certain lifestyle recommendations can help support overall liver health:

• Maintain a balanced diet rich in fruits, vegetables, and whole grains
• Limit alcohol consumption
• Exercise regularly
• Maintain a healthy weight
• Avoid unnecessary medications and supplements
• Get vaccinated against hepatitis A and B
• Practice safe sex and avoid sharing needles to prevent viral hepatitis transmission

By implementing these lifestyle changes and following medical advice, individuals can often improve their liver health and normalize AST levels over time.

The Role of AST in Monitoring Liver Disease Progression

AST levels play a crucial role in monitoring the progression of various liver diseases and assessing the effectiveness of treatments. Regular AST testing, along with other liver function tests, can provide valuable insights into disease activity and liver health over time.

Chronic Viral Hepatitis

In chronic hepatitis B and C infections, AST levels are used to:

• Assess disease activity and inflammation
• Monitor response to antiviral therapy
• Detect potential complications or reactivation

Nonalcoholic Fatty Liver Disease (NAFLD)

For patients with NAFLD, AST levels can help:

• Differentiate between simple steatosis and nonalcoholic steatohepatitis (NASH)
• Monitor disease progression and response to lifestyle interventions
• Identify patients at higher risk of fibrosis and cirrhosis

Alcoholic Liver Disease

In alcoholic liver disease, AST levels are used to:

• Assess the severity of liver damage
• Monitor abstinence and recovery
• Detect potential relapse or disease progression

The frequency of AST monitoring in these conditions depends on the specific disease, its severity, and the treatment plan. Healthcare providers may adjust the monitoring schedule based on individual patient needs and response to treatment.

Emerging Research and Future Directions in AST Testing

As our understanding of liver diseases and biomarkers continues to evolve, researchers are exploring new ways to utilize AST and other liver enzymes for improved diagnosis and monitoring of liver conditions. Some areas of ongoing research include:

Novel Biomarker Panels

Researchers are investigating combinations of biomarkers, including AST, to develop more accurate and specific diagnostic panels for various liver diseases. These panels aim to improve early detection and differentiation between different liver conditions.

Non-invasive Fibrosis Assessment

AST is being incorporated into non-invasive fibrosis scoring systems, such as the AST to Platelet Ratio Index (APRI) and FIB-4 score. These tools help estimate the degree of liver fibrosis without the need for invasive liver biopsies.

Personalized Medicine Approaches

Ongoing studies are exploring how individual variations in AST levels and other biomarkers can be used to tailor treatment approaches and predict disease outcomes more accurately.

Point-of-Care Testing

Advancements in technology are leading to the development of rapid, point-of-care AST tests that could allow for more frequent and convenient monitoring of liver health, particularly in resource-limited settings.

As research in these areas progresses, we can expect to see more refined and personalized approaches to liver disease diagnosis, monitoring, and treatment based on AST and other liver function tests.

In conclusion, understanding AST ranges and their implications is crucial for effective liver health assessment and management. By combining AST results with other liver function tests, clinical findings, and emerging research, healthcare providers can offer more accurate diagnoses and personalized treatment plans for patients with liver conditions. Regular monitoring of AST levels, along with lifestyle modifications and appropriate medical interventions, can significantly improve outcomes for individuals with liver diseases and help maintain overall liver health.

Standard liver tests

Clin Liver Dis (Hoboken). 2016 Jul; 8(1): 13–18.

, M.D.
¹
and , M.D.
^1
,
2
,
3

George Kasarala

¹
Vidant Medical Center,
East Carolina University,
Greenville,
NC,

Hans L. Tillmann

¹
Vidant Medical Center,
East Carolina University,
Greenville,
NC,

²
Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine,
East Carolina University,
Greenville,
NC,

³
Greenville VA Health Care, Center,
Greenville,
NC,

¹
Vidant Medical Center,
East Carolina University,
Greenville,
NC,

²
Division of Gastroenterology, Hepatology and Nutrition, Department of Medicine,
East Carolina University,
Greenville,
NC,

³
Greenville VA Health Care, Center,
Greenville,
NC,

Corresponding author.^*Hans L. Tillmann, M.D. , Mail Stop 628, Internal Medicine–Gastroenterology, Hepatology, and Nutrition, Vidant Medical Center, TA 338, Greenville, NC 27834. E‐mail: ude.uce@41hnnamllit

Received 2016 Jan 31; Revised 2016 Apr 28; Accepted 2016 May 6.

Copyright © 2016 by the American Association for the Study of Liver DiseasesThis article has been cited by other articles in PMC.

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Abbreviations

AIH

autoimmune hepatitis

ALT

alanine aminotransferase

AMA

antimitochondrial antibodies

AP

alkaline phosphatase

AST

aspartate aminotransferase

DILI

drug‐induced liver injury

ERCP

endoscopic retrograde cholangiopancreatography

gGT

γ‐glutamyl transpeptidase; LIT, liver injury test

MELD

Model for End‐Stage Liver Disease

MRCP

magnetic resonance cholangiopancreatography

NASH

nonalcoholic steatohepatitis

PBC

primary biliary cholangitis

ULN

upper limit of normal

The liver is the largest organ in the body and arguably the most important organ for protein production and detoxification, both of which are facilitated by a myriad of enzymes. Both the detection of enzymes released from liver cells and proteins produced by the liver and released into the blood can be used to analyze liver health.

Standard liver tests (Tables and ) that assess injury to the liver include alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatases (APs). The excretory function of the liver can be estimated by bilirubin and the metabolic function of the liver by clotting tests and albumin.

Table 1

Standard Liver Tests, Their Sources of Origin, and Abnormalities

Table 2

Elevation of Liver Chemistries With Liver Diseases

Tests that describe injury of the liver such as aminotransferases and AP have historically been mislabeled liver injury tests (LIT). In contrast, standard tests such as albumin, bilirubin, and prothrombin time are useful in evaluating liver function.

The pattern of elevation of the different enzymes can be used to discriminate hepatocellular from cholestatic or mixed injury; AST and ALT are more elevated in patients with hepatocellular injury, whereas AP and γ‐glutamyl transpeptidase (gGT) are more elevated in cholestatic injury.

Discrimination of Normal Versus Healthy Values

Normal values for laboratory results are defined as those found in 95% of a population. Thus, 2.5% of a population will be above and below the normal values, respectively. But being outside the normal does not immediately reflect illness; that is, a bilirubin level below normal has no clinical consequences. Contrarily, being within the normal value does not necessarily reflect a healthy state. In that regard it has been suggested to use an upper limit of 19 and 30 U/L for ALT for women and men, respectively,¹ to reflect healthy values. This also fits the observed increased mortality in individuals with ALT values that are normal but above the healthy range.² Thus, liver transaminases likely will be described as healthy (≤19 U/L for women and ≤30 U/L for men) and normal values (i.e., <65 U/L). The normal values will depend on the specific laboratory population, thus limiting standardization.

For some assessments such as drug safety, the times upper limit of normal (ULN) is established to define safety margins. Substituting the healthy range values for normal range value will therefore need to be carefully addressed in the future.

Mild abnormalities in liver‐related tests may warrant repeat testing before a more extensive workup is initiated. Abnormal liver chemistries may occur in 1% to 4% of the asymptomatic population.³, ²¹

Markers of Hepatocellular Injury

Transaminases are involved in transferring the amino groups of aspartate and alanine to ketoglutaric acid. Although ALT is more liver specific, elevated ALT levels are also reported in myopathies (Table ).⁴, ⁵

Table 3

Disease Association According to Aminotransferases Elevation Pattern

Hepatocyte injury results in altered cell membrane permeability causing the excessive leakage of transaminases. Periportal hepatocytes (zone 1) have relatively more ALT, whereas the hepatocytes near the central vein (zone 3) have more AST (Fig. ). Thus, causes of hepatic inflammation that are predominantly involving zone 1 such as viral and autoimmune hepatitis result in predominantly ALT elevation. In contrast, ischemic or toxic insults are more likely to involve zone 3, causing a predominance of AST elevation. AST/ALT ratio, also known as De Ritis ratio, is useful in assessing various liver diseases.⁶ In alcoholic hepatitis, AST is usually higher than ALT, with the AST/ALT ratio reaching 2:1. In acute viral hepatitis, ALT levels are usually higher than AST. High AST/ALT ratio (>1.5) in acute viral hepatitis may be indicative of potential fulminant course.⁹ AST/ALT ratio greater than 1.0 in chronic liver diseases may be indicative of advanced fibrosis.⁸, ⁹ AST and ALT are also used together with platelets to assess the likelihood of advanced liver fibrosis and are part of the aspartate aminotransferase‐to‐platelet ratio index (APRI) and FIB‐4 score:

Zone 1 has more ALT than AST, and zone 3 has more AST than ALT. Autoimmune and viral hepatitis predominantly involve zone 1 (ALT > ALT). Ischemic and toxic events, heart failure, and Budd‐Chiari syndrome predominantly involve zone 3 (AST > ALT). AP is mostly present on basolateral membrane of hepatocytes lining the bile canaliculi. Reproduced from PLoS Biology. Copyright 2005, Frevert et al.

Aminotransferases are normal or only mildly elevated in obstructive jaundice except in acute phase of biliary obstruction caused by the passage of gallstone into the common bile duct.¹⁰ In this case, aminotransferases may reach values greater than 1000, decreasing quickly, with liver test rapidly evolving into those of typical cholestasis or normalizing completely.

Aminotransferases levels also vary with age, sex, race, and body mass index.¹¹ Levels are found to be higher in obese patients and lower in dialysis patients,¹² whereas ALT levels are noted to decline with weight loss.¹³ AST levels are 15% higher in African American males as compared with Caucasians. ¹¹ Some individuals may have asymptomatic AST elevation caused by a defect in clearance of the enzyme.¹⁴ Transaminases levels can be very high in patients with acute viral hepatitis, drug‐induced liver injury, hepatic ischemia, and Budd‐Chiari syndrome (Fig. ). In asymptomatic patients with no underlying disease, mild aminotransferase elevation for more than 6 months warrants further investigation.²²

Typical AST elevation and De Ritis ratios for different kinds of liver diseases.

Algorithms for evaluation of elevated aminotransferases (A), AP (B), and bilirubin (C), respectively. Abbreviations: AIH, autoimmune hepatitis; AMA, antimitochondrial antibodies; DILI, drug‐induced liver injury; ERCP, endoscopic retrograde cholangiopancreatography; MRCP, magnetic resonance cholangiopancreatography; NASH, nonalcoholic steatohepatitis; PBC, primary biliary cholangitis.

Markers of Cholestasis

AP is the standard liver test reflecting cholestasis and can be complemented by gGT. gGT is part of a typical liver panel in some countries, whereas in the United States the standard liver test usually includes only AST, ALT, and AP. Because gGT is diffusely located in endoplasmic reticulum of bile ductal cells, its elevation is less specific for cholestasis but supports the suspicion that an elevated AP is liver derived as opposed to being of extrahepatic origin (Tables and ).¹⁵

Table 4

Elderly individuals older than 60 years, especially women, may have a mildly elevated AP. ¹⁶ Individuals with blood types O and B may have an elevation of the serum AP after eating a fatty meal because of the influx of intestinal AP into circulation.⁷ AP can also be nonpathologically elevated in children and adolescents undergoing rapid bone growth¹⁶ and in women late in normal pregnancies because of the influx of placental AP.¹⁷

Markers of Liver Function

Bilirubin, albumin, and prothrombin time are standard tests to evaluate the liver function.

Bilirubin is the result of enzymatic breakdown of heme. Bilirubin is conjugated in the liver, resulting in water solubility. The conjugated bilirubin is then secreted into the bile. In healthy individuals, conjugated bilirubin comprises a small proportion of total bilirubin.¹⁸

In adults, unconjugated bilirubin elevation is most often of extrahepatic origin, mainly caused by hemolysis. In the absence of hemolysis, isolated unconjugated hyperbilirubinemia in an otherwise healthy patient should raise the suspicion for Gilbert syndrome. Up to 5% of the population has Gilbert syndrome, which is due to partial defects in uridine 5′‐diphosphate‐glucuronosyltransferase, the enzyme that conjugates bilirubin.¹⁹ Crigler‐Najjar syndrome is a rare cause of unconjugated hyperbilirubinemia.

In adults, conjugated hyperbilirubinemia is almost always a sign of biliary obstruction or impaired hepatic function. Two rare hereditary conditions cause defects in the secretory mechanism, Dubin‐Johnson syndrome and Rotor syndrome, which result in elevated conjugated bilirubin.

Total serum bilirubin with increased prothrombin time correlates with poor outcomes in alcoholic hepatitis.¹⁸ Both are also critical components of Model for End‐Stage Liver Disease (MELD) score and Child‐Pugh score.

Serum albumin is exclusively synthesized by hepatocytes, but the long half‐life of albumin makes it difficult to interpret in the setting of acute liver injury. In chronic liver disease, albumin is the first of the three standard liver function tests to decline in advancing liver cirrhosis, before increase in bilirubin or prothrombin time. Albumin less than 35 g/dL should raise suspicion for cirrhosis. Differential diagnosis for hypoalbuminemia includes protein malnutrition of any cause, as well as protein‐losing enteropathies, nephrotic syndrome, and chronic infection.

With the exception of factor VIII, all coagulation factors are synthesized in the liver. Because of the short half‐lives of the coagulation factors, these are the best parameters to measure synthetic function of liver in acute conditions. This is most frequently done by prothrombin time determination. Because most clotting factors synthesized in the liver depend on vitamin K, prothrombin time is affected by vitamin K deficiency or use of vitamin K inhibitors. Vitamin K deficiency is seen in patients with chronic cholestasis or fat malabsorption from disease of the pancreas or small bowel. Prothrombin time is a better indicator of hepatic dysfunction than the international normalized ratio (INR),²⁰ despite INR having become a crucial part of the MELD score used for prioritizing liver allocations. In acute and chronic liver disease, prolonged prothrombin time (>5 seconds), which does not respond to parenteral vitamin K, is a poor prognostic sign.

Notes

Potential conflict of interest: Nothing to report.

REFERENCES

1.
Prati D,
Taioli E,
Zanella A,
Della Torre E,
Butelli S,
Del Vecchio E, et al. Updated definitions of healthy ranges for serum alanine aminotransferase levels. Ann Intern Med
2002;137:1-10.
[PubMed] [Google Scholar]2.
Kim HC,
Nam CM,
Jee SH,
Han KH,
Oh DK,
Suh I. Normal serum aminotransferase concentration and risk of mortality from liver diseases: prospective cohort study. BMJ
2004;328:983.
[PMC free article] [PubMed] [Google Scholar]3.
Kundrotas LW,
Clement DJ. Serum alanine aminotransferase (ALT) elevation in asymptomatic US Air Force basic trainee blood donors. Dig Dis Sci
1993;38:2145-2150.
[PubMed] [Google Scholar]4.
Lin YC,
Lee WT,
Huang SF,
Young C,
Wang PJ,
Shen YZ. Persistent hypertransaminasemia as the presenting findings of muscular dystrophy in childhood. Acta Paediatr Taiwan
1999;40:424-429.
[PubMed] [Google Scholar]5.
Scola RH,
Werneck LC,
Prevedello DM,
Toderke EL,
Iwamoto FM. Diagnosis of dermatomyositis and polymyositis: a study of 102 cases. Arq Neuropsiquiatr
2000;58(3B):789-799.
[PubMed] [Google Scholar]6.
De Ritis F,
Coltorti M,
Giusti G. An enzymic test for the diagnosis of viral hepatitis: the transaminase serum activities. J Infect Dis
1957;101:219-223.
[PubMed] [Google Scholar]7.
Matsushita M,
Komoda T. [Relationship between the effects of a high‐fat meal and blood group in determination of alkaline phosphatase activity]. Rinsho Byori
2011;59:923-929.
[PubMed] [Google Scholar]9.
Botros M,
Sikaris KA,
Lu ZX,
McNeil A. The short term prognostic usefulness of the De Ritis ratio. Clin Biochem Rev
2013;34:S18.
[Google Scholar]10.

Anciaux, M. L.
,

Pelletier, G.
,

Attali, P.
,

Meduri, B.
,

Liguory, C.
, &

Etienne, J. P.

Prospective study of clinical and biochemical features of symptomatic choledocholithiasis. Dig Dis Sci
1986;31:449-453.
[PubMed] [Google Scholar]11.
Siest G,
Schiele F,
Galteau MM,
Panek E,
Steinmetz J,
Fagnani F, et al. Aspartate aminotransferase and alanine aminotransferase activities in plasma: statistical distributions, individual variations, and reference values. Clin Chem
1975;21:1077-1087.
[PubMed] [Google Scholar]12.
Yasuda K,
Okuda K,
Endo N,
Ishiwatari Y,
Ikeda R,
Hayashi H, et al. Hypoaminotransferasemia in patients undergoing long‐term hemodialysis: clinical and biochemical appraisal. Gastroenterology
1995;109:1295-1300.
[PubMed] [Google Scholar]13.
Palmer M,
Schaffner F. Effect of weight reduction on hepatic abnormalities in overweight patients. Gastroenterology
1990;99:1408-1413.
[PubMed] [Google Scholar]14.
Vajro P,
Lofrano MM,
Fontanella A,
Fortunato G. Immunoglobulin complexed AST (“macro‐AST”) in an asymptomatic child with persistent hyper‐transaminasemia. J Pediatr Gastroenterol Nutr
1992;15:458-460.
[PubMed] [Google Scholar]15.
Levinson M,
Holbert J,
Blackwell C,
Wruble LD. Serum gamma‐glutamyl transpeptidase: its specificity and clinical value. South Med J.
1979;72:837-841.
[PubMed] [Google Scholar]16.
Moss DW. Alkaline phosphatase isoenzymes. Clin Chem
1982;28:2007-2016.
[PubMed] [Google Scholar]17.
Fishman WH,
Bardawil WA,
Habib HG,
Anstiss CL,
Green S. The placental isoenzymes of alkaline phosphatase in sera of normal pregnancy. Am J Clin Pathol
1972;57:65-74.
[PubMed] [Google Scholar]18.
Pratt DS. Evaluation of liver function In: Kasper D, Fauci A, Hauser S, Longo D, Jameson J, Loscalzo J, eds. Harrison’s Principles of Internal Medicine, 19th ed
New York, NY: McGraw‐Hill; 2015.
[Google Scholar]19.
Monaghan G,
Ryan M,
Seddon R,
Hume R,
Burchell B. Genetic variation in bilirubin UPD‐glucuronosyltransferase gene promoter and Gilbert’s syndrome. Lancet
1996;347:578-581.
[PubMed] [Google Scholar]20.
Robert A,
Chazouilleres O. Prothrombin time in liver failure: time, ratio, activity percentage, or international normalized ratio?
Hepatology
1996;24:1392-1394.
[PubMed] [Google Scholar]21.
Hultcrantz R,
Glaumann H,
Lindberg G,
Nilsson LH. Liver investigation in 149 asymptomatic patients with moderately elevated activities of serum aminotransferases. Scand J Gastroenterol
1986;21:109-113.
[PubMed] [Google Scholar]22.
Mathiesen UL,
Franzen LE,
Fryden A,
Foberg U,
Bodemar G. The clinical significance of slightly to moderately increased liver transaminase values in asymptomatic patients. Scand J Gastroenterol
1999;34:85-91.
[PubMed] [Google Scholar]

Aspartate Aminotransferase Level – an overview

Hepatitis.

INH has infrequent major toxicities, most notably hepatitis. Ten to 20 percent of INH recipients have asymptomatic minor elevations in serum aspartate aminotransferase levels that usually resolve even with continued therapy.³⁰ A meta-analysis of six studies estimated the rate of clinical (symptomatic) hepatitis in patients given INH alone to be approximately 0.6%.³¹ Recent data indicate that the incidence of clinical hepatitis is even lower. Hepatitis occurred in only 0.1% to 0.15% of 11,141 persons receiving INH alone as treatment for LTBI in an urban tuberculosis control program.³² Early estimates of the incidence of severe or major INH hepatotoxicity were provided from the results of a large multicenter U.S. National Institutes of Health (NIH)–sponsored trial. Fatal hepatitis occurred in 8 of nearly 14,000 patients receiving INH.³³ All but one of the deaths occurred in one study center, and patients did not receive routine monitoring for toxicity during the trial.³³ More recent studies, however, suggest that the rate of fatal INH-related hepatitis is substantially lower.^32,34,35 The likely explanation is the adoption in the early 1980s of uniform clinical toxicity monitoring for patients receiving INH for treatment of LTBI.^34,35 Hepatotoxicity can occur at any time but generally occurs after weeks to months of therapy rather than days to weeks after treatment is begun. INH hepatotoxicity is correlated with age, presumably owing to a diminished capacity for repair of INH-induced hepatocellular damage in the elderly. Undernutrition may also play a role in the expression of INH hepatotoxicity.³⁶ Hepatotoxicity is increased in several groups: alcoholic patients; patients with preexisting liver damage³³; pregnant women and women up to 3 months postpartum³⁷; patients also taking INH in combination with acetaminophen³⁸; patients receiving other potentially hepatotoxic agents such as rifampin³⁵; patients with active hepatitis B; and HIV-seropositive patients on highly active antiretroviral therapy.³⁹ Histologically, hepatocellular damage can progress to submassive necrosis. Although active hepatitis B is considered a contributing factor to INH hepatotoxicity,^40,41 INH has been safely administered to some with acute hepatitis⁴² and for LTBI to persons chronically infected with hepatitis B and C. ^39,43,44 Educating patients about the recognition of symptoms of INH-induced liver disease is key in preventing its progression. As noted, routine clinical monitoring of patients receiving INH is mandatory.³⁵ Routine monitoring of serum hepatic enzyme concentrations is not indicated for all patients at the start of treatment of LTBI. Baseline testing is recommended for patients whose initial evaluation suggests a liver disorder, patients infected with HIV who are receiving highly active antiretroviral therapy, pregnant women and those in the immediate postpartum period (i.e., within 3 months of delivery), persons with a history of chronic liver disease (e.g., hepatitis B or C, alcoholic hepatitis, or cirrhosis), persons who use alcohol regularly, and others who are at risk for chronic liver disease.^35,39 Baseline testing is no longer routinely indicated in persons older than 35 years of age.^35,39 Laboratory monitoring during treatment of LTBI is indicated for patients whose baseline liver function test results are abnormal and for other persons at risk for hepatic disease. ^35,39,45 Although biochemical monitoring may contribute to patient confidence and adherence with the treatment regimen, the contribution of routine biochemical monitoring to the safety of INH administration is not proven. The importance of routine clinical monitoring is clear, however, and must be applied rigorously with or without biochemical monitoring.

The most feared INH-related toxicity is fulminant hepatic failure necessitating liver transplantation or resulting in death. The CDC conducted a detailed analysis of 17 patients with severe INH-related hepatoxicity over a 4-year period.⁴⁶ The estimated incidence of death and liver transplantation was 1/150,000 to 1/220,000 patients receiving INH therapy for LTBI. Although continuation of INH after the onset of hepatitis-related symptoms was associated with severe hepatotoxicity, some patients still developed severe hepatotoxicity after stopping INH within days to a week of symptom onset. Although it is not universally protective, patients should be strongly advised to discontinue INH therapy at the onset of symptoms consistent with incipient hepatitis, such as nausea, loss of appetite, and dull midabdominal pain. Perhaps most disconcerting, there were two children younger than 15 years of age in this series of patients. The overall conclusions of this analysis were that severe hepatotoxicity was idiosyncratic, occurred at any time during INH treatment, occurred even with careful clinical and biochemical monitoring and with appropriate (recommended) doses of INH, and could occur in children.⁴⁶

Most hepatotoxicity subsides after INH discontinuation. Cautious readministration of INH after a resolution of hepatitis for selected patients has been reported to be well tolerated and safe,⁴⁷ although consideration should be given in these patients to alternative therapies for LTBI, such as rifampin.^35,39 Recognition of the frequency and severity⁴⁸ of INH hepatotoxicity has not curtailed therapeutic usage but has led to a revision of indications for treatment of LTBI, with special caution indicated for groups identified at high risk for INH hepatotoxicity (see earlier discussion). ^35,39,48

Aspartate Aminotransferase (AST)

Aspartate Aminotransferase (AST)

Chemistry

6240 RCP

356-3527

Collection Medium:

Alternate
Collection Media:

Call laboratory for additional acceptable specimen collection containers.

Minimum:

3 mL light green top tube or 1 light green top
Microtainer^® for
pediatric patients

Testing Schedule:

24 hrs/day, 7 days a week, including holidays.

Turn Around
Time:

1 hour (upon receipt in laboratory)

Reference Range:

Males; 0-40 U/L
Females; 0-32 U/L

Pediatric Ranges:
Age               Male/Female U/L
1-3 years              10-50
4-6 years              10-45
7-12 years             10-40
13-18 years            10-35

Comments:

Avoid hemolysis. Adult reference ranges changed 11/26/2013.

This test is also performed in the Iowa
River Landing (IRL) clinical laboratory (for specimens drawn at that
site).

Test
Limitations:

Criterion: Recovery within plus or minus 10% of initial value.

Hemolysis interferes due to AST activity from erythrocytes (index of 
50).

Icterus: No significant interference up to an I index of 60 
(approximate conjugated and unconjugated bilirubin concentration: 60 
mg/dL).

Lipemia (Intralipid): No significant interference up to an L index of 
250 (approximate triglycerides concentration: 500 mg/dL). There is 
poor correlation between turbidity and triglycerides concentration. 
Lipemia may cause absorbance flagging as a result of an absorbance 
increase.

Reference
Glick MR, Ryder KW, Jackson SA. Graphical Comparisons of Interferences 
in Clinical Chemistry Instrumentation. Clin Chem 1986;32:470-474.

Methodology:

Spectrophotometric

Laboratory medicine – Knowledge @ AMBOSS

Last updated: October 12, 2021

Summary

Laboratory medicine involves the analysis and evaluation of body fluids such as blood, urine, and cerebrospinal fluid (CSF), the results of which are important for the prevention, diagnosis, and staging of diseases. Even though laboratory medicine plays an important role in daily clinical practice, the evaluation of results should always take into account the patient’s medical history as well as clinical and diagnostic findings. This article covers important laboratory parameters, such as hematological parameters, iron studies, coagulation studies, parameters of certain organ functions, and inflammatory markers. Further parameters of clinical relevance may be found in other articles and are listed in the section “Overview of important laboratory parameters.” If not otherwise indicated, the reference ranges provided here are consistent with those used by the NBME.

Overview of important laboratory parameters

Covered in this article

Covered in other articles

Hematological parameters

Complete blood count (CBC)

• A laboratory test that measures:
• In a CBC with differential, the percentage of WBC subtypes (e.g., neutrophils, lymphocytes, etc.) is also included.

RBC parameters

WBC parameters

WBC count and differential

^[4]

For causes of eosinophilia, think CHINAA: Collagen vascular disease (e.g., eosinophilic granulomatosis), Helminths, Hyper-IgE syndrome, Neoplasms, Allergies, Addison disease.

Neutrophil left shift

Leukemoid reaction

^[14]

Leukoerythroblastic reaction

Platelet count

Pancytopenia

• Definition: a decrease in the number of cells of all cell lines (i.e., RBCs, WBCs, and platelets) in the peripheral blood
• Causes

Peripheral blood smear

• Manual examination of a peripheral blood sample under a microscope
• May reveal pathognomonic RBC morphologies, which can be used to identify certain types of anemia that automated RBC indices cannot
• Examples of findings

Iron studies

In combination with an elevated TIBC, low hemoglobin, ferritin, and iron levels are diagnostic of iron deficiency anemia.

Elevated ferritin levels do not rule out iron deficiency anemia. Ferritin can be elevated in response to simultaneous chronic inflammation.

Coagulation studies

Most common tests

Additional tests

• Bleeding time: amount of time it takes for a bleeding to stop after a small skin puncture
• Anti-factor Xa assay: used to monitor certain anticoagulant therapies
• D-dimer: fibrin degradation product that correlates with activity of coagulation and fibrinolysis
• Ristocetin cofactor assay: measures the ability of von Willebrand factor (vWF) to agglutinate platelets
• Coagulation factor assays: e.g., reduced factor VIII activity in hemophilia A
• Clot observation test: simple method of point-of-care testing to assess coagulation, especially if hyperfibrinolysis is suspected
  • Procedure: A small amount of blood is collected in a test tube and examined macroscopically after a few minutes.
  • Interpretation
• Thromboelastography: full blood assay that assesses the formation, stability, and dissolution of a thrombus alongside PT and aPTT
• Rumpel-Leede test: detects primary hemostasis disorders and increased dermal capillary fragility
  • Procedure: A tourniquet is applied to the upper arm and the cuff is inflated to a pressure that is midway between the patient’s systolic and diastolic blood pressure. After 5 minutes, the tourniquet is removed and the cubital pit and forearm are examined for petechiae.
  • Interpretation
    • Test is positive if ≥ 10 petechiae appear per square inch.
    • Positive test results occur in:

Liver function tests

• Damage to hepatocytes results in the release of various enzymes that are then detectable in the blood.
• These parameters may help to evaluate the cause and severity of hepatic cell damage.

AST/ALT ratio

Indirect bilirubin is water-insoluble.

• Liver dysfunction can reduce the hepatic production of various substances, which is reflected in their decreased serum levels.
• The initial evaluation of liver synthesis capacity typically consists of determining serum albumin, PT/INR, and platelet count.
• For a more exhaustive list of substances produced by the liver, see the article on the “Liver.”

Pancreatic parameters

• This table lists parameters that are commonly tested to evaluate pancreas function and disease. For a more exhaustive list of substances produced by the pancreas, see the article “Pancreas.”

Other metabolic parameters

• Basic metabolic panel (BMP) measures the serum concentrations of:
• Comprehensive metabolic panel (CMP) measures all parameters included in the BMP plus:
• Clinical use: Metabolic parameters are used to diagnose and monitor a wide variety of conditions. They are particularly useful in the diagnosis of:

Electrolytes

• Electrolytes develop when a salt dissolves in a solution, causing it to separate into cations (positively charged) and anions (negatively charged).
• Normal body function requires the appropriate concentrations of the following electrolytes: sodium (Na⁺), potassium (K⁺), chloride (Cl^–), bicarbonate (HCO₃^–), calcium (Ca²⁺), magnesium (Mg²⁺), and phosphate (H₂PO₄^–, HPO₄^2-).
• More detailed information about electrolyte imbalances can be found in dedicated articles.

Chloride (Cl

^–)

• Reference range: 95–105 mg/dL (95–105 mmol/L)
• Physiology
  • Cl^– is the main anion in the extracellular space and is the counterpart to the main extracellular cation Na⁺.
    • Changes in serum chloride levels typically reflect changes in serum sodium levels.
    • An exception to this is in acid-base disorders, which can be caused by or lead to changes in chloride levels independent of sodium.
  • Cl^– is involved in water balance, maintaining osmotic pressure, and acid-base balance.

Magnesium (Mg

²⁺)

For more details regarding hypomagnesemia, see the article “Hypomagnesemia.”

Hypermagnesemia

• Common causes
• Clinical features
• Treatment

Phosphate (H

₂PO₄^–, HPO₄^2-)

• Normal range: 3.0–4.5 mg/dL (1.0–1.5 mmol/L)
• Physiology

For more on the effects and treatment of low phosphate levels, see “Hypophosphatemia.”

Hyperphosphatemia

• Common causes
• Clinical features
  • Often asymptomatic
  • High PO₄^3- levels cause the formation of an insoluble compound with calcium, which can lead to:
• Treatment

Lactic acid (lactate)

General

Hyperlactatemia

• Common causes
• Clinical features: Symptoms are largely caused by lactic acidosis and compensatory mechanisms. They can include:

Inflammatory markers

Inflammatory markers are used in the diagnosis and monitoring of a large spectrum of conditions, including infection, autoimmune diseases, and malignancies. Most inflammatory processes lead to elevated CRP, elevated ESR, and leukocytosis.

Acute phase reaction

^[25][26]

• Definition: systemic response to systemic and/or local disturbances (e.g., acute or chronic inflammation, infection, surgery, trauma, malignancy)
• Diagnostic use

Positive acute phase reactants

Hepatic production and serum levels of positive acute phase reactants increase in response to inflammatory processes.

Important positive acute phase reactants: “Upstream, Fred Hopes He Catches Some Perfect Fish.” (Upregulation, Ferritin, Haptoglobin, Hepcidin, C-reactive protein, Serum amyloid A, Procalcitonin, Fibrinogen)

Negative acute phase reactants

Serum levels of negative acute phase reactants decrease in response to inflammatory processes.

Erythrocyte sedimentation rate (ESR)

^[31]

• Description: distance that erythrocytes (RBCs) descend in a vertical tube of anticoagulated blood over one hour
• Normal ranges
  • ♀ 0–20 mm/h
  • ♂ 0–15 mm/h
• Common causes of increase
  • All conditions associated with ↑ fibrinogen (e.g., infection, inflammation, malignancies)
    • Normally, RBCs are separated from each other by their negatively charged surfaces.
    • Elevated fibrinogen levels lead to a decrease in the negative charges, causing RBCs to aggregate and sink faster in the test tube.
  • Inflammation
  • Infection
  • Malignancies (e.g., multiple myeloma, Waldenstrom macroglobulinemia, metastases)
  • Autoimmune diseases; (e.g., SLE, rheumatoid arthritis, giant cell arteritis, polymyalgia rheumatica, de Quervain thyroiditis)
  • Anemia
  • Macrocytosis
  • Renal disease (e.g., nephrotic syndrome, ESRD)
  • Pregnancy (leads to ↑ fibrinogen)
  • Old age
• Common causes of decrease

What are normal ranges for AST and ALT? – MVOrganizing

What are normal ranges for AST and ALT?

What are normal levels of AST (SGOT) and ALT (SGPT)? The normal range of values for AST (SGOT) is about 5 to 40 units per liter of serum (the liquid part of the blood). The normal range of values for ALT (SGPT) is about 7 to 56 units per liter of serum.

Which is worse AST or ALT?

The AST level is higher than the ALT level, and the ratio is greater than 2:1 in 70% of patients. A ratio greater than 3 is strongly indicative of alcoholic hepatitis.

What if AST is higher than ALT?

An AST/ALT ratio higher than one (where the AST is higher than ALT) is suggestive of cirrhosis. An AST/ALT ratio higher than 2:1 (where the AST is more than twice as high as the ALT) is suggestive of alcoholic liver disease.

How can I lower my AST and ALT levels naturally?

Natural methods include:

1. Drinking coffee. Drinking coffee can help to lower ALT levels.
2. Exercising regularly.
3. Losing excess weight.
4. Increasing folic acid intake.
5. Making dietary changes.
6. Reducing high cholesterol.
7. Taking care with medications or supplements.
8. Avoiding alcohol, smoking, and environmental toxins.

Can AST levels return to normal?

In acute hepatitis, AST levels usually stay high for about 1-2 months but can take as long as 3-6 months to return to normal.

When should I be concerned about AST levels?

High levels of AST in the blood may indicate hepatitis, cirrhosis, mononucleosis, or other liver diseases. High AST levels can also indicate heart problems or pancreatitis. If your results are not in the normal range, it doesn’t necessarily mean that you have a medical condition needing treatment.

How quickly can AST increase?

AST levels increase when there’s damage to the tissues and cells where the enzyme is found. AST levels can rise as soon as six hours after damage to tissue occurs. The normal range for AST is higher from birth to age 3 compared to the normal ranges for older children and adults.

How quickly can AST levels drop?

AST levels can fluctuate between 5 and 10% from one day to the next in the same individual. Moderate exercise increases AST levels for as long as 24 hours, usually less than 3 times the upper limit of normal. The half-life of AST in the circulation is 17 +/- 5 hours.

Do AST levels go down?

Aspartate Transaminase (AST): Very high levels of AST (more than 10 times normal) are usually due to Acute Hepatitis, sometimes due to a viral infection. With acute Hepatitis, AST levels usually stay high for about 1-2 months but can take as long as 3-6 months to return to normal.

How do I bring my AST levels down?

The good news is that many people can lower their elevated ALT with changes in their lifestyle and exercise:

1. Limit alcohol consumption.
2. Lose weight.
3. Quit smoking.
4. Get regular exercise.
5. Consider taking probiotic supplements to improve your digestive health.
6. Eat a healthy diet.

Is 150 a high ALT level?

In addition, increased ALT levels (>150 IU/L) have a positive predictive value (PPV) of 95% for a biliary aetiology of acute pancreatitis. Isolated hyperbilirubinaemia can be predominantly unconjugated (>80% of total) or conjugated (>50%), and does normally not reflect significant liver disease.

Is Alt 75 high?

Chronic hepatitis and liver cirrhosis. Very high levels (>75 times upper reference limit) suggest ischaemic or toxic (poison or medicine related) injury to the liver. Ischaemic liver damage is mostly seen in patients with other serious illnesses such as septicaemia or collapse.

Is ALT level of 36 high?

Normal Results The normal range is 4 to 36 U/L. Normal value ranges may vary slightly among different laboratories.

Is 50 a high ALT level?

Alanine aminotransferase (ALT) is an enzyme found mainly in the liver. High levels (>50) indicate damage to liver cells as a result of infection (hepatitis, infectious mononucleosis, etc.) or toxic levels of drugs (e.g. acetaminophen [Tylenol]) or chemicals (e.g. chloroform) or alcohol.

Is ALT level of 58 high?

A person with a healthy liver will have an ALT level in the normal range. The normal range can vary from laboratory to laboratory. According to the Mayo Clinic, the normal range for adult males is 7–55 units per liter. Females may have a lower upper limit normal than males.

What is a bad ALT level?

ALT blood levels are a marker of liver health: low levels typically indicate a healthy liver, while high levels suggest liver damage [3]. The normal range is around 7-35 U/L in women and 7-40 U/L in men. There may be some lab-to-lab variability in ranges due to differences in equipment, techniques, and chemicals used.

Is Alt 53 high?

A normal ALT test result can range from 7 to 55 units per liter (U/L). Levels are normally higher in men. Slightly high ALT levels may be caused by: Alcohol abuse.

Is ALT of 30 high?

One recent population study excluded people at risk for NAFLD and concluded that the “healthy range” for serum ALT should be up to 30 U/L for men and 19 U/L for women3.

Is 65 a high ALT level?

What then is an elevated ALT level? The lack of standardization among laboratories, Dr Di Bisceglie conceded, is part of the problem. Different labs can define anywhere from 40 to 65 U/L as normal.

Aspartate Aminotransferase (AST) | HealthLink BC

Test Overview

An aspartate aminotransferase (AST) test measures the amount of this enzyme in the blood. AST is normally found in red blood cells, liver, heart, muscle tissue, pancreas, and kidneys. AST formerly was called serum glutamic oxaloacetic transaminase (SGOT).

Low levels of AST are normally found in the blood. When body tissue or an organ such as the heart or liver is diseased or damaged, additional AST is released into the bloodstream. The amount of AST in the blood is directly related to the extent of the tissue damage. After severe damage, AST levels rise in 6 to 10 hours and remain high for about 4 days.

The AST test may be done at the same time as a test for alanine aminotransferase, or ALT. The ratio of AST to ALT sometimes can help determine whether the liver or another organ has been damaged. Both ALT and AST levels can test for liver damage.

Why It Is Done

An aspartate aminotransferase (AST) test is done to:

• Check for liver damage.
• Help identify liver disease, such as hepatitis. Liver disease may produce symptoms such as pain in the upper abdomen, nausea, vomiting, and sometimes jaundice.
• Check on the success of treatment for liver disease.
• Find out whether jaundice was caused by a blood disorder or liver disease.
• Keep track of the effects of cholesterol-lowering medicines and other medicines that can damage the liver.

How To Prepare

Tell your doctor:

• All of the medicines and natural health products (such as echinacea and valerian) you are taking.
• If you are allergic to any medicines.
• If you are or might be pregnant.

Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results may mean. To help you understand the importance of this test, fill out the medical test information form .

How It Is Done

The health professional taking a sample of your blood will:

• Wrap an elastic band around your upper arm to stop the flow of blood. This makes the veins below the band larger so it is easier to put a needle into the vein.
• Clean the needle site with alcohol.
• Put the needle into the vein. More than one needle stick may be needed.
• Attach a tube to the needle to fill it with blood.
• Remove the band from your arm when enough blood is collected.
• Put a gauze pad or cotton ball over the needle site as the needle is removed.
• Put pressure on the site and then put on a bandage.

How It Feels

The blood sample is taken from a vein in your arm. An elastic band is wrapped around your upper arm. It may feel tight. You may feel nothing at all from the needle, or you may feel a quick sting or pinch.

Risks

There is very little chance of a problem from having blood sample taken from a vein.

• You may get a small bruise at the site. You can lower the chance of bruising by keeping pressure on the site for several minutes.
• In rare cases, the vein may become swollen after the blood sample is taken. This problem is called phlebitis. A warm compress can be used several times a day to treat this.

Results

An aspartate aminotransferase (AST) test measures the amount of this enzyme in the blood. Results are usually available within 12 hours.

Normal

The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what’s normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.

High values

High levels of AST may be caused by:

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

• Taking large doses of vitamin A.
• Taking some natural health products, such as echinacea and valerian.
• Recent cardiac catheterization or surgery.

What To Think About

• The aspartate aminotransferase (AST) test is more effective than the alanine aminotransferase (ALT) test for detecting liver damage caused by heavy alcohol use. The AST to ALT ratio may sometimes help determine if liver damage is related to alcohol use disorder. For more information, see the topic Alanine Aminotransferase (ALT).
• The gamma glutamyl transferase (GGT) test is sometimes done along with other liver enzyme tests.
• Many different conditions can raise AST blood levels, so other testing is usually needed to interpret an abnormal AST result.

References

Citations

1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

• Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
• Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
• Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby.

Credits

Current as of:
September 23, 2020

Author: Healthwise Staff
Medical Review:
E. Gregory Thompson MD – Internal Medicine
Anne C. Poinier MD – Internal Medicine
Adam Husney MD – Family Medicine
Martin J. Gabica MD – Family Medicine
Kathleen Romito MD – Family Medicine
Jerome B. Simon MD, FRCPC, FACP – Gastroenterology

Current as of: September 23, 2020

Author: Healthwise Staff

Medical Review:E. Gregory Thompson MD – Internal Medicine & Anne C. Poinier MD – Internal Medicine & Adam Husney MD – Family Medicine & Martin J. Gabica MD – Family Medicine & Kathleen Romito MD – Family Medicine & Jerome B. Simon MD, FRCPC, FACP – Gastroenterology

Blood Tests Explained | South Mountain Equine

Blood Tests
Your horse may have a blood sample taken for a number of reasons, including illness, monitoring response to treatment and general health or fitness checks. Blood can be tested for many different substances. This guide aims to explain what things are being measured and what abnormal results may mean.
Reference ranges are often supplied, indicating the normal values of measurement for a horse. These values are often for the average horse so naturally some horses will fall outside these brackets without any significance. Results should all be interpreted with reference to the other results as many of the things measured have direct effects on one another.
Red Blood Cells
A number of measurements can be made with regard to red blood cells (erythrocytes) in the horse:
Packed Cell Volume (PCV) – This is the percentage of the blood that is made up of red blood cells. This figure can vary from as low as 24% up to 48%.
Red Blood Cell (RBC) Count – This is the number of red blood cells in a given volume, typically 1 litre, of blood.
A low PCV and RBC count normally indicate anaemia. Anaemia may be caused by blood loss, such as trauma or bleeding into the gastrointestinal tract, immune mediated disease, various infections, some cancers or many other conditions. Your horse may shoe signs of anaemia such as weakness, dullness, reduced appetite or reduced exercise tolerance.
An increase in PCV and RBC count may be due to several factors. It usually means either that the horse is dehydrated or that the horse has been ‘wound up’ prior to taking the blood sample. In these cases the spleen contracts, releasing more red blood cells into the circulation. Rarely, other conditions can cause an increase in the PCV and RBC count.
Mean Corpuscular Volume (MCV) – This is the average volume of each red blood cell sampled.
Differences in the average red blood cell volume explain why the PCV and RBC count do not always match. This can also be used to help identify causes of anaemia.
Mean Corpuscular Haemoglobin (MCH) – This is the average amount of haemoglobin in each red blood cell.
Mean Corpuscular Haemoglobin Concentration (MCHC) – This is the amount of haemoglobin in the circulating blood.
Haemoglobin is the substance in red blood cells that allows them to carry oxygen around the body. These measurements can be useful in identifying causes of anaemia or in identifying mineral deficiencies, such as iron deficiency.
White Blood Cells
There are five different types of white blood cells (leukocytes) in the horse. The number of these different cells in the blood, and their numbers with reference to one another can give us a lot of information about your horse’s wellbeing.
White Blood Cell Count (WCC) – This is the total number of white blood cells in the blood. Increases in the WCC (leukocytosis) are most commonly a result of bacterial or viral infection, stress, drug administration or immune mediated disease. A decrease in the total numbers of white blood cells (leukopaenia) may be due to overwhelming bacterial or viral infection, bone marrow disease or endotoxaemia.
Neutrophils – These are the most common white blood cells in the horse. They move rapidly to sites of infection or inflammation within the body. A low number of neutrophils (neutropaenia) is most often a result of an increase in demand for them. Where there has been a sudden infectious or inflammatory process the neutrophils in the blood may have been used up in dealing with this. There is a natural delay whilst the body adapts to this by synthesising and releasing more neutrophils. Failure of neutrophil production and endotoxaemia may also lead to neutropaenia. Neutrophilia is an increase in the numbers of circulating neutrophils. This is most often due to bacterial or viral infection, injury, stress or drug administration. Some bone marrow conditions may result in overproduction of neutrophils and thus a neutrophilia.
Monocytes – These cells are important in the breakdown of damaged tissues and the destruction of microbes. An increase in monocyte numbers (monocytosis) may indicate bacterial infection, chronic inflammation or stress. Monocytosis may also be seen during the recovery phase following viral infection. Monocytopaenia, low numbers of circulating monocytes, is not clinically significant as no monocytes may be found in the examination of blood from clinically normal horses.
Eosinophils – These cells are most commonly associated with parasitic disease and with allergic conditions. Increased numbers (eosinophilia) may be due to parasitism (although this is not always seen in these cases) or hypersensitivity (allergic) reactions. As with monocytes, eosinophils are not always found in a blood sample from clinically normal horses so eosinopaenia is not a significant finding.
Basophils – Basophils are rarely found in blood samples. When they are found in increased numbers (basophilia) , this may indicate long standing allergic disease or ongoing recovery from colic.
Lymphocytes – These are the white blood cells with the greatest responsibility for managing the immune system. Lymphocytosis (increased numbers of lymphocytes) can be caused by excitement and exercise or some cancers. Lymphocytosis is a common incidental finding in young horses. Lymphopaenia, reduced lymphocyte numbers, may be a result of stress, viral infection, severe and overwhelming bacterial infection an endotoxaemia.
Platelets
Platelets have a number of important functions such as blood clotting and the release of various beneficial chemicals at the site of injuries. Thrombocytopaenia is a reduction in circulating platelets, often due to immune mediated disease causing platelet destruction. In some cases toxins or some cancers result in decreased platelet production form bone marrow. Rarely an increase in numbers of circulating platelets is seen. This is most commonly due to bacterial infection.
Biochemical Tests
Substances that are measured in a sample of your horse’s blood may indicate the function of specific organs or metabolic pathways. As many substances can come from more than one source, results must be interpreted with caution and with careful reference to other results from the blood test.
Adrenocorticotropic hormone (ACTH) – This hormone is tested for in the diagnosis and management of Cushing’s disease. It is elevated in horses with uncontrolled Cushing’s disease.
Alkaline Phosphatase (ALP) – Raised levels of ALP may indicate bone metabolism, intestinal malfunction or, most commonly, chronic liver disease. Reference ranges vary widely with age.
Aspartate aminotransferase (AST) – Elevated AST levels are seen in cases of acute liver or muscle damage. Levels peak 24 – 48 hours following injury and will return to normal 10 – 21 days following resolution. Combined with CK measurements, AST provides a useful measurement of muscle damage in cases of ‘tying up’.
Bilirubin – Bilirubin, excreted from the liver in bile, may be increased in the horse in cases of anorexia or some liver conditions.
Bile acids – These are excreted as bile salts in the bile. Their measurement can be useful in assessing liver function.
Cortisol – Blood cortisol levels may be increased in horses with Cushing’s disease or in stressed horses.
Creatine Kinase (CK) – CK occurs in high levels in skeletal and cardiac muscle. In the horse, increased levels almost always signify acute muscle damage. Levels peak 6 – 12 hours following injury and can return to normal levels in 3 – 4 days. CK is often assessed alongside AST when assessing muscle damage.
Creatinine – Creatinine is excreted from the blood by the kidneys. Increased levels of creatinine may be seen in horses with primary kidney disease or with other conditions affecting the kidneys such as dehydration, shock and post renal obstructions.
Gamma Glutamyl-transferase (GGT) – GGT is found in certain liver cells. Increased blood levels indicate liver disease. Following an increase in GGT levels, it can take several weeks for these levels to return to normal. Increases may also be seen in association with over training.
Glucose – Glucose is the source of the body’s energy. It is measured in suspected cases of equine metabolic syndrome and sometimes in cases of equine Cushing’s disease. Blood glucose may also be measured as part of a glucose tolerance test, assessing small intestinal function.
Glutamate Dehydrogenase (GLDH) – Raised GLDH levels are specific for acute liver disease. Following resolution of any liver injury, levels of GLDH return to normal within 24 hours, so may be a useful indicator of ongoing liver disease.
Insulin – This hormone may be tested for during investigation of equine metabolic syndrome, in which cases it is elevated. High insulin levels may be responsible for laminitic episodes in some horses and ponies.
Lactate – Lactate is constantly produced and broken down by the body. Blood lactate levels may be taken from horses with colic, where an increasing blood lactate concentration may indicate a worsening prognosis.
Lactate Dehydrogenase (LDH) – This enzyme is present in a number of tissues and must be separated into its different isoenzymes, which are linked to different organs. Dependant on the specific isoenzyme raised, elevated LDH may indicate liver, muscle or intestinal disease.
Protein – Total Protein (TP) – Total protein is a numerical value for the total mass of protein in a given volume of blood. Alterations in the total protein value may represent changes in the values of one or several of the proteins found in blood:
Albumin – Raised levels of albumin are almost always due to dehydration. When levels of albumin are low this suggests either a failure of protein production due to liver disease or protein loss. Protein can be lost from the body most commonly through the intestine or can be lost through the kidney.
Globulin – Globulin proteins carry out a number of tasks, including assisting with immune function. Total globulin is made up of three fractions, alpha, beta and gamma globulin. Levels of these fractions can be measured using a process called serum protein electrophoresis. Increased globulin levels may be seen when a horse is fighting an infection. When newborn foals have a blood test to ensure adequate colostrum transfer from the mare levels of gamma globulin are measured. When these levels are low this indicates inadequate transfer of immunity through the mare’s colostrum and the foal may require transfusion of plasma with increased gamma globulin levels.
Inflammatory Proteins – Several proteins in horse blood may be measured to give information on inflammatory conditions. These include serum amyloid A (SAA) and fibrinogen. SAA rises quickly in response to inflammation or infection and will quickly return to normal levels following resolution of the inflammation or infection. Fibrinogen will rise in response to tissue damage. Fibrinogen rises slowly, reaching a peak after about 10 days and takes around 3 weeks to return to normal levels.
Triglycerides – Triglycerides are responsible for fat transport in the body. Raised triglyceride levels are commonly seen following a period of anorexia as body fat is mobilised for energy.
Urea – Urea is produced in the liver and excreted by the kidneys. Elevated levels may signify kidney disease but may also occur with dehydration or fasting.
Electrolytes
Calcium – In the blood the majority of this electrolyte is bound to albumin, so levels should be assessed with reference to albumin levels. Increased calcium levels may be seen in cases of kidney disease, some cancers and vitamin D poisoning. Low levels may be due to liver disease, inadequate intake or late pregnancy/lactation.
Chloride – This electrolyte is closely associated to sodium, and will usually mirror changes in this. Low chloride levels are commonly seen in horses following excessive sweating.
Phosphate – Low phosphate may be seen in horses with kidney disease or with low dietary phosphate intake. Low phosphate can be a normal finding in horses where the blood sample has been taken immediately after exercise.
Potassium – Very little of the body’s potassium is in the blood, so changes in the blood potassium levels may not correlate with total body potassium. Low levels are due to potassium loss. This can be through intestine or kidney disease or through sweating. High levels may be an incidental finding when red blood cells have broken down (haemolysed) in the sample prior to testing or may be due to muscle damage.
Sodium – Low levels commonly indicate loss through excessive sweating, or through kidney or intestinal disease. Low levels may also be found in young foals with bladder damage. Increased sodium levels are usually a sign of dehydration.

Observation astronomical telescope of visible and infrared range

VISTA – the Visible and Infrared Survey Telescope for Astronomy – is part of the Paranal Observatory (ESO). VISTA is the world’s largest observation telescope operating in the near infrared region of the spectrum. The large diameter of its main mirror, large field of view and ultra-sensitive receivers allow for a completely new view of the southern sky.

The telescope is mounted on the top of a mountain next to the one that houses ESO’s Very Large Telescope (VLT). Naturally, the exceptional observational conditions at these neighboring peaks are the same.

The main mirror of VISTA has a diameter of 4.1 m. In photographic terms, the telescope is a 67-megapixel digital camera with a 13,000 mm f / 3.25 reflex lens.

The heart of the VISTA telescope is a giant three-ton camera with 16 state-of-the-art high-sensitivity infrared detectors.

Scientific research with VISTA

The VISTA observation time is completely devoted to the systematic mapping of the sky. The lion’s share of the telescope’s time is spent compiling the six largest publicly available sky surveys. In the framework of some of them, small regions of the sky are studied for a long time in order to register extremely faint objects; the rest cover the entire southern sky. In the process of observations, huge amounts of new data are created, which are used in research related to various fields of astronomy, from the study of small bodies in the solar system to cosmological studies of the nature of dark matter and dark energy.Many new objects are being discovered in our Galaxy with the VISTA telescope, various ideas about the origin of dark matter are being tested. With VISTA, astronomers will be able to build a 3D map of about 5% of the entire observable volume of the Universe. VISTA is a powerful tool for finding distant quasars and studying the evolution of galaxies and galaxy clusters. Finding very distant galaxy clusters is essential for understanding the nature of dark energy.

The VISTA Telescope was conceived and designed by a consortium of 18 UK universities under the leadership of Queen Mary, University of London and became a penniless contribution from the UK under its agreement to join ESO.The design and construction were supervised by the UK Astronomy Technology Center under the Science and Technology Facilities Council’s (STFC, UK ATC).

The telescope was provisionally put into operation on December 10, 2009 and is now in the possession of ESO.

Scientific tasks

Sky views: variable stars, deep views, brown dwarfs, etc.

More about VISTA

• VISTA: main mirror
• VISTA: camera
• VISTA: overviews
• VISTA: Consortium

• For Scientists: Observers wishing to use VISTA see Paranal Instrumentation page

Not only Hubble: space telescopes of the present and future

RBC Trends has compiled a selection of eight existing and upcoming space telescopes that have changed or will change the way we think about space

In 1610, Galileo Galilei and Simon Marius independently discovered the moons of Jupiter, which became one of the most important scientific events of the time.Almost four centuries later, the launch of the Hubble Space Telescope marked the beginning of a new revolution in astronomy.

The main problem of optical astronomy is the inhomogeneity of the earth’s atmosphere. Regions with different densities and air velocities lead to the twinkling of stars, visible to the naked eye. This makes space the only place where a telescope can get a really clear and comprehensive view of the universe.

This article tells about the most significant projects of space telescopes, while the largest ground-based observatories are devoted to a separate review.

Also, astrophysicist Sergei Popov told RBC Trends about how new technologies have turned astronomy into a fashionable and popular science. Why not expect that in the future we will “move” to another planet, and what is the use of these astronomical discoveries in general to all of us?

Release of the podcast “There will be no lectures” RBC Trends with Sergei Popov on why we can never move to another planet:

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Hubble Space Telescope

The Hubble Telescope, named after Edwin Hubble, was launched into orbit on April 24, 1990. It is a joint project between NASA and the European Space Agency, conceived as a general observatory for the exploration of the Universe in the visible, ultraviolet and infrared wavelengths. Included in the number of NASA Large Observatories.

Hubble telescope

(Photo: NASA)

On May 20, 1990, the telescope took the first photograph of the star cluster NGC 3532.

Left – image taken from Las Campanas Observatory, Chile. Right – part of the first image of “Hubble”

(Photo: NASA, ESA, and STScI)

The Hubble orbits the Earth at an altitude of about 540 km and is tilted 28.5 degrees to the equator.It takes 95 minutes to complete one revolution.

The Orbiting Telescope has conducted over 1 million observations and provided data that astronomers have used to write over 18,000 peer-reviewed scientific publications (from planet formation to giant black holes). These documents were mentioned in other publications over 900 thousand times.

What is Hubble known for

• Thanks to the study of pulsating stars, it was possible to determine the age of our Universe – 13.8 billion years.
• In January 1992, astronomers confirmed the existence of planets outside the solar system.
• The telescope recorded a rare event – the collision of comet Shoemaker-Levy 9 with Jupiter in 1994. These are the first ever photographs of the collision of two objects in the solar system.

A series of images taken with NASA’s Hubble Space Telescope show the evolution of the impact region of comet Shoemaker-Levy

(Photo: H.Hammel, MIT and NASA)

• The telescope recorded in detail the evolution of Jupiter’s weather, including a rare storm near the planet’s equator.
• Hubble showed Pluto for the first time since the discovery of the planet in 1930.
• The spacecraft photographed a 400 km high plume of gas and dust from the eruption of Io, Jupiter’s largest inner moon.

Images taken on February 14, 2007. On the left are orange oval sulfur deposits around the Pele volcano. The right image shows a large plume rising above the surface near the North Pole.

(Photo: NASA, ESA, and J.Spencer (SwRI))

• Confirmed the assumptions about the presence of supermassive black holes in the cores of galaxies.
• Found the most distant space object known to date – the galaxy GN-z11. Now we see it as it was 13.4 billion years ago.

The galaxy GN-z11, shown in the inset, is visible 13.4 billion years ago, just 400 million years after the Big Bang, when the universe was only 3% of its present age.Given the expansion of the universe, it is now actually 32 billion light years away.

(Photo: NASA, ESA, P. Oesch (Yale University))

• Confirmed the existence on Jupiter’s moon Ganymede of a huge underground ocean under a 150-kilometer layer of ice.Based on this discovery, astronomers have added the largest satellite in the solar system to the list of possible candidates for the search for life forms.
• Discovered water vapor on exoplanet K2-18b from the habitable zone, as well as the first confirmed interstellar comet 2I / Borisov.

On June 13, 2021, the Hubble scientific equipment computer stopped responding to commands from Earth. The engineering and scientific group servicing the telescope managed to fix the breakdown only by July 16, 2021.

Orbiting Hubble has two Twitter accounts – Hubble NASA and Hubble ESA, two official YouTube channels – NASA and ESA, and Instagram and Facebook accounts.

NASA video dedicated to “Hubble”

Hubble Space Telescope images and data show galaxies as they were billions of years ago.

Chandra Space X-ray Observatory

The Chandra Observatory is a telescope specially designed to detect X-rays from very hot regions of the Universe, such as exploding stars, galaxy clusters and matter around black holes. The observatory got its name in honor of one of the greatest astrophysicists of the 20th century, Subrahmanyan Chandrasekhar, famous for his work on white dwarfs. Included in the number of NASA Large Observatories.

Telescope “Chandra”

(Photo: NGST)

Launched on July 23, 1999.The telescope was supposed to last five years. As a result, “Chandra” became the longest astronomical mission without supporting expeditions.

On account of “Chandra” thousands of captured space objects and phenomena that have helped scientists to better understand the structure of our Universe and the processes occurring in it. The telescope shows the remnants of exploding stars, detects black holes throughout the universe, tracks the separation of dark matter in colliding galaxies, and much more.

What is Chandra known for

• Chandra’s first image of a supernova remnant Cassiopeia A showed astronomers a mysterious source at the center, which could be a rapidly rotating neutron star or black hole.

A snapshot of a supernova remnant Cassiopeia A

(Photo: John Hughes et al.(Rutgers), NASA / CXC / SAO)

• In the Crab Nebula, it was possible to distinguish shock waves around the central pulsar, invisible to other telescopes.
• Using the Chandra X-ray Observatory, scientists have refined the Hubble constant, a number that determines the rate of expansion of the Universe.
• When superclusters of galaxies collide, evidence of the existence of dark matter was obtained.
• Thanks to the data from the telescope, scientists have observed the largest X-ray burst ever detected in a supermassive black hole in the center of the Milky Way galaxy.

The supermassive black hole Sagittarius A * is located at the center of our galaxy.Scientists estimate that its mass is about 4.5 million times the mass of our sun.

(Photo: NASA)

• Images showing a highly distorted supernova remnant, dubbed W49B, have led scientists to speculate that it contains the very last black hole from the Milky Way galaxy.
• A new type of black hole has been discovered in the galaxy M82.

You can follow Chandra’s life on Twitter, on the YouTube channel, as well as on Instagram and Facebook.

Fermi Space Telescope

The Fermi Telescope is an international multicenter observatory that studies space in the gamma-ray range.

The device was originally called the Gamma-ray Large Area Space Telescope or GLAST. But on August 26, 2008, NASA renamed the telescope in honor of the Italian physicist Enrico Fermi, winner of the 1938 Nobel Prize in Physics.

Fermi Telescope

(Photo: NASA)

The telescope was launched on June 11, 2008.Since then, “Fermi” orbits the Earth at an altitude of 565 km. It scans the entire sky every three hours looking for gamma rays with energies ranging from 20 MeV to over 300 GeV. The telescope makes one revolution around our planet in 95 minutes.

By mapping the entire sky every three hours, Fermi discovers the most extreme phenomena in the universe: from gamma-ray bursts and jets of black holes to pulsars, supernova remnants and the origin of cosmic rays.

What Fermi is known for

• The telescope’s first scientific result was the registration of a gamma-ray pulsar located in the supernova remnant CTA 1, which became the first known object to “blink” only in gamma rays.
• On September 15, 2008, Fermi recorded a record gamma-ray burst in the constellation Carina, designated GRB 080916 ° C. The power of the explosion exceeded the power of about 9 thousand ordinary supernovae.
• “Fermi Bubbles”. In 2010, scientists discovered a giant, mysterious structure that looks like a pair of bubbles above and below the center of our galaxy. Each lobe is 25,000 light-years high, and together they extend about half the diameter of the Milky Way.

• On March 7, 2012, the telescope observed a flare with the highest energy ever seen in a solar eruption.At the peak of the outburst, Fermi detected gamma rays 2 billion times the energy of visible light, or about 4 GeV.
• The telescope has observed numerous gamma-ray bursts (short bursts during a thunderstorm associated with lightning) on ​​Earth. He found that they could produce 100 trillion positrons (the antiparticle of the electron, refers to antimatter), much more than scientists previously thought.

Fermi does not have the same active social life as its colleagues. The telescope has a Twitter account (not updated since autumn 2019) and a Facebook page (last updated in September 2020).

Orbital Telescope TESS

TESS (Transiting Exoplanet Survey Satellite) is a space telescope designed for the discovery of exoplanets by the transit method (fixing characteristic dips in brightness caused by the passage of a planet against the background of a star). Developed by scientists at MIT as part of the NASA Minor Research Program.

Telescope TESS

(Photo: NASA)

Orbiting Telescope was launched on April 18, 2018 aboard a SpaceX Falcon 9 rocket.TESS is the first NASA Astrophysics satellite launched under contract with SpaceX.

Telescope observes space objects from highly elliptical near-earth orbit (HEO). For the first time, the gravitational attraction of the Moon is used as a trajectory stabilizing force

In the first year of operation, the telescope observed the southern hemisphere of the celestial sphere. The area of ​​the sky was divided into 13 sectors, for each of which TESS spent 27 days. On July 18, 2019, the first phase of the mission was completed.By the same principle, the telescope worked for a year in the Northern Hemisphere. Since August 2020, the device has embarked on an extended mission, which is expected to last until September 2022.

As a result, TESS covered about 75% of the sky with its gaze, discovered about 66 confirmed exoplanets and recorded evidence of more than 2,100 candidate planets orbiting bright neighboring stars. In the future, the James Webb Telescope will study these candidate planets and determine whether they can support life.

What TESS is known for

• On September 18, 2018, a group of astronomers led by Chelsea Huang of MIT reported the first exoplanet discovered by the telescope in the Pi Mensae star system, about 60 light-years from Earth.

NASA video about the first successes of TESS

• On April 15, 2019, NASA announced the first discovery of an Earth-sized planet by TESS.Planet HD 21749c makes up about 89% of the Earth’s diameter and orbits HD 21749, a K-type star (i.e. orange stars with a surface temperature of 3800 to 5000 K) with a mass of about 70% of the Sun, located 53 light years away in the southern constellation Reticulum, the planet is most likely hot, with surface temperatures up to 427 ° C.
• On January 6, 2020, NASA announced the discovery of TOI 700 d, the first Earth-sized exoplanet in the habitable zone discovered by TESS. The exoplanet orbits the star TOI 700, 100 light years away in the constellation Dorado.
• In January 2021, scientists determined that TYC 7037-89-1 is the first six-star system ever discovered in which all stars participate in eclipses.

Three such pairs make up a recently discovered sixfold star system called TYC 7037-89-1.

(Photo: NASA)

The telescope has a Twitter account.You can also find information on TESS activities on the NASA Exoplanets Facebook page.

Orbital Observatory “Spektr-RG”

The orbital astrophysical observatory “Spektr-RG” is designed to build a complete map of the Universe in the X-ray energy range. This is a project of the Federal Space Program of Russia with the participation of Germany.

The observatory consists of two mirror telescopes: the German eROSITA, operating in the soft X-ray range, and the Russian ART-XC, operating in the hard X-ray range.ART-XC is the first telescope in Russia with oblique incidence optics.

Spektr-RG with telescopes ART-XC (bottom) and eROSITA (top)

(Photo: RKS)

On July 13, 2019, the observatory was launched from the Baikonur cosmodrome.

Research “Spectra-RG” will last 6.5 years. Of these, the telescope will scan the starry sky for four years, and for the remaining 2.5 years it will operate in the mode of point observation of objects in the Universe at the request of the world scientific community. The location for the device is the Lagrange point (L2), 1.5 million km from the Earth.

According to Roskosmos, during the Spektr-RG mission, it will detect about 100 thousand massive clusters of galaxies, about 3 million supermassive black holes in the nuclei of galaxies, hundreds of thousands of stars with active corona, tens of thousands of star-forming galaxies and many other objects, including of unknown nature, and also explores in detail the properties of hot interstellar and intergalactic plasma.

It is expected that in 2025 the most accurate map of the Universe, built by the Spectra-RG telescopes, will be completed and published.

James Webb Telescope

The James Webb Telescope (JWST) is an ambitious scientific project for NASA’s orbiting infrared observatory in collaboration with the European and Canadian space agencies. The launch is scheduled no earlier than November 2021.

James Webb Telescope

(Photo: NASA)

Unlike Hubble, Webb is not serviceable.The refrigerant supply will last for about ten years. To ensure correct operation during this period, all critical subsystems of the telescope are duplicated.

Regular scientific data and imagery is expected to begin arriving from Webb approximately six months after launch.

The James Webb Telescope will be the largest, most powerful and sophisticated space telescope ever built and launched into space. The size of the main mirror is 6.5 m wide and has a collecting surface area of ​​25 sq.m, will allow “Webb” to observe distant galaxies at a distance of more than 13 billion light years.

The telescope will be located 1.5 million km from the Earth in the opposite direction from the Sun at the second Lagrange point (L2). He will see about 39% of the sky at any given time. Since the telescope must turn away from warm and close objects that can interfere with it, it will not be able to observe the Sun, Mercury, Venus, Earth or the Moon.

Transport and Sequence of Deployment of the James Webb Telescope in Orbit

Four scientific instruments have unique features that will enable astronomers to study various space objects:

1. The Near Infrared Camera (NIRCam) will track light from stars in nearby galaxies and from distant stars in the Milky Way.It will also seek light from stars and galaxies that formed early in the life of the universe.
2. The near-infrared spectrograph (NIRSpec) will observe up to 100 objects simultaneously and search for galaxies formed after the Big Bang.
3. A mid-infrared spectrograph (MIRI) will take photographs of distant celestial objects, as Hubble is currently doing. It will allow scientists to gather physical details about distant objects in the Universe, discover distant galaxies, faint comets, newborn stars and objects in the Kuiper belt (the far part of the solar system beyond the orbit of Neptune).
4. Precision Aiming Sensor with Near Infrared Imaging and Slitless Spectrograph (FGS / NIRISS). The FGS component will be responsible for ensuring that the telescope looks exactly in a given direction during scientific research. And NIRISS is to look for traces of the first light in the Universe and explore exoplanets.

The telescope has a Twitter account, YouTube channel, Instagram and Facebook pages.

Xuntian Optical Telescope

Telescope of the Chinese Space Station (CSST) “Xuntian” or “Heavenly Sentinel” – an autonomous orbital module with an optical telescope.

Xuntian is scheduled to launch in 2024. The telescope will revolve around the Earth in the same orbit as the Chinese modular station. He will be able to periodically approach and dock with it, so that the crew will carry out the necessary repairs and change instruments.

Xuntian Telescope

(Photo: CSNA)

Huge lens makes the Sky Sentry comparable to the Hubble.At the same time, the view of the Chinese telescope will be 300 times larger with the same high resolution. Thanks to the wide field of view, he will be able to observe up to 40% of the space for ten years.

The telescope of the China Space Station will conduct observations in near ultraviolet and visible light, as well as investigate the properties of dark matter, the formation and evolution of galaxies.

Spectrum-UF Space Observatory

The Spektr-UV international space observatory project will explore the Universe in the ultraviolet and visible ranges of the electromagnetic spectrum with a high angular resolution, as well as register gamma radiation in the energy range from 10 keV to 10 MeV.The main work on the project is being carried out by Russia and Spain.

“Spectrum-UV”

(Photo: WSO-UV)

The space telescope with a 1.7 m mirror will be equipped with high and low resolution spectrographs to acquire high resolution spectra and cameras to produce high quality images in the ultraviolet range.It will be able to compete with the Hubble telescope.

Spectr-UV will not search for planets, but will study the physicochemical composition of planetary atmospheres in the Solar System and beyond, the physical and chemical properties of interstellar and circumstellar matter (gas and dust particles), the nature of active galactic nuclei, chemical evolution galaxies. An important task of Spectra-UF is the search for hidden matter, that is, gas and dust, which are difficult to distinguish for already existing telescopes.

The launch dates of the Spektr-UF mission were postponed several times.The observatory is expected to begin operation in the fall of 2025. The launch is planned from the Vostochny cosmodrome.

90,000 Hubble is 30 years old. How his pictures are created that change our view of the world

• Anastasia Soroka
• BBC

April 24, 2020

Photo author, NASA / STScI

Photo caption,

Hubble jubilee snapshot – “Cosmic Reef”, which captures the great red nebula NGC 2014 and its smaller blue neighbor NGC 2020 in the Large Magellanic Cloud.

The Hubble Space Telescope is 30 years old. On April 24, 1990, the shuttle Discovery delivered the telescope into orbit – since then, Hubble has been looking into the depths of the universe and sending photographs of what it saw to Earth.

But the mechanical eye of the telescope does not see what we will eventually see – people are behind the breathtaking images. An entire team of scientists from the Space Telescope Science Institute (STScI) in Baltimore and amateur astronomers around the world are working on this.Their task is to decipher the astronomical data collected by Hubble and hidden in its black-and-white, grainy images. And translate them into a visual language understandable for a 12-year-old student who sees a picture in a textbook.

In other words, color images of galaxies and stars are created by people, not Hubble itself. But this is not just “coloring” black and white pictures in “Photoshop”. Every color and shade in the radiance of celestial bodies in Hubble’s photographs is based on science and a strict set of rules, as well as a play of imagination and many original creative solutions.For example, how to designate an insignificant difference in the brightness levels of several celestial objects so that it is distinguishable by the eye? Or with what colors to describe the range of ultraviolet radiation invisible to humans?

How humanity sees the Universe in which it lives and itself in it depends on the results of this work.

On Hubble’s birthday, we spoke to the head of the STScI image processing team to find out how images that change the way we view the world are created.

Mechanical eye

Click

“Pillars of Creation” in the Eagle Nebula, 2014

Snapshot after processing

The picture taken on the channel of ultraviolet range

“I am a mechanical eye. I, a machine, show you the world as only I can see it.I liberate myself from today forever from human immobility, I am in continuous motion, I am approaching and moving away from objects … […] … freed from time and space frames, I compare any points of the universe, wherever I fix them. My path is to create a fresh perception of the world. So I decipher the world unknown to you in a new way, “- this is a quote from the 1923 manifesto of the Russian-Soviet director from Odessa, one of the founders of documentary films Dziga Vertov.

In the same 1923, Herman Obert, one of the fathers of rocketry, published The book “Rocket for Interplanetary Space” is one of the first scientific works substantiating the possibility of creating a rocket on liquid fuel.In it, he mentioned that a telescope could be sent into orbit with a rocket.

Just as Dziga Vertov’s movie camera became a mechanical extension of the human eye, allowing it to “rise with airplanes” and “move with the muzzle of a running horse,” the lens of the Hubble telescope is an optical-mechanical eye that allowed us to expand the time frame and space – to look into the distant worlds of the Universe and into its past. Hubble Lenses are a time machine that explores the birth of long-extinct stars.

Click

Image of NGC 2174, or the Monkey Head Nebula, in the constellation Orion. year 2014

Snapshot after processing

Image taken with Wide Angle and Planetary Camera 2

“The Perfect Storm”

NASA names Hubble’s “conception” in 1946, when the first scientific article by Princeton astrophysicist Lyman Spitzer was published on the benefits of launching a large telescope into space, outside the restless earth’s atmosphere.The first working group of astrophysicists and engineers met three decades later, in 1977, to discuss the creation of the Large Space Telescope. A few years later, it will be renamed in honor of the American astronomer Edwin Hubble, who proved that there are other galaxies outside our galaxy that are moving away from the Milky Way with increasing speed. This discovery opened the way for deep space exploration.

But it was not in vain that so many years between conception and embodiment were passed.According to the head of the STScI news service, astronomer Ray Willard, who has been working on the project for more than 30 years, the birth of the Hubble was “the perfect storm”: the telescope could see space objects with unprecedented clarity, scientists could see them in color. And the Internet made it possible to instantly show these images to all of humanity. This, Willard argues, was the Hubble Revolution.

Photo author, NASA / STScI

Photo caption,

“First light”: left – a picture from the Las Campanas ground observatory in Chile; on the right – the first image of the Hubble from orbit.

On May 20, 1990, less than a month after launching into orbit, Hubble sent the “first light” to Earth – its first image taken while adjusting the focus of the telescope. This photograph turned out to be 50% sharper than images from ground-based telescopes (although it soon became clear that the Hubble’s main mirror had a defect that made the images slightly blurry – but this was fixed).

Photo author, NASA / STScI

Photo caption,

A ring of gas around the center of the 1987A supernova explosion on the outskirts of the Tarantula nebula in the Large Magellanic Cloud.Snapshot of 1990.

In August of that year, Hubble made one of its first discoveries, capturing a luminous elliptical ring of gas 1.3 light years in diameter around the center of the 1987A supernova explosion on the outskirts of the Tarantula Nebula in the Large Magellanic Cloud. This was the first of thousands of miracles that mankind will see through a telescope – each of the following more and more clear, more and more detailed.

Many of these images, such as the Pillars of Creation or the Horsehead Nebula, will become iconic and will be reproduced in millions of copies on T-shirts, cups and smartphone cases.

Hubble has rediscovered the universe precisely because of its incredible imagery and its accessibility, ”Ray Willard says. – They go beyond science, they talk about the wonders of the universe, without going into all the smallest facts of science. Some people just like these images because they are pictures, because of their intuitiveness, their expressiveness. They turn to some on a spiritual level. “

Light is a color

” People often ask [about Hubble photos]: does it really look like this? Says Ray Willard.“But this is a pointless question. We are talking about a huge range of brightness and colors invisible to the human eye. Even if you fly close to these objects, you will not see any color, because it will spread everywhere around you. “

The light of distant space objects – giant nebulae, colliding galaxies, dying stars – that Hubble sees is too intense or on the contrary, it is too dim for the weak human eye, therefore, when observing through a telescope from Earth or even through a window from a spacecraft, we will see, at best, only vague imprints of these disasters.

Creating a “true” color image from astronomical data is as much an art as it is a science, according to STScI. Willard said the task of Hubble data scientists – like any photographer’s task – is “to capture the essence of the subject.” To be able to combine scientific fact with aesthetic pleasure. Often for this you need to enhance a particular color, highlight a shade, emphasize contrast.

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Colliding galaxies NGC 2936 and NGC 2937 in the constellation Hydra.Snapshot 2013

Snapshot after processing

Snapshot with Wide-angle camera 3

Willard says he and his team were inspired by technicolor technology invented in Hollywood for color films in the 1930s, such as The Wizard of Oz.

And also – the work of the American photographer Ansel Adams, known for ultra-clear black-and-white photographs of the nature of the American West.Willard compares images of the Hubble galaxies with images of the Grand Canyon of Adams.

“The Grand Canyon is an incredible geologic form. I can’t do anything in Photoshop to make the Grand Canyon look better. It is what it is. But I can use photography and Photoshop to try and highlight all of its amazing details that tell its story “, – he explains the approach to processing space images.

True and False Colors

Click

Galaxy NGC 3147 in the constellation Draco.2019 year

Snapshot after processing

The picture taken on the channel of ultraviolet range

Each of the millions of Hubble sources is black and white. Collecting color images from them is possible thanks to the red, green and blue filters through which these images are passed and which repeat the three types of light-sensitive cells on our retina.Choosing the right filter, or a combination of them, is up to the researchers and can be quite simple – or very complex.

The color of an object depends on how it emits or absorbs light. Thus, the planets absorb waves of light from their stars of one length and reflect – another: the blue shades of Neptune and Uranus are associated with methane in their atmosphere, which absorbs red light.

Nebulae can have a very rich and bright color, since they emit light of only a certain wavelength, shining like glowing neon lamps, clouds of gases – hydrogen, oxygen, nitrogen.

The color of a star, on the other hand, will be rather desaturated, fluctuating in pastel colors, because stars emit an incredible amount of light in the entire visible range, stimulating all the light-sensitive cells on our retina. But these are simple tasks.

And what color should be used to designate light waves of infrared or ultraviolet radiation invisible to humans that Hubble sees? Or show the difference in brightness levels so that it is noticeable and scientifically sound at the same time?

In such cases, scientists have to resort to the help of false colors, that is, to apply color solutions where they are not there, or where they do not make any sense – in order to emphasize an imperceptible contrast between light and shadow or differences in different parts of a complex space object.

Differences in shades of color are easier for the human eye than in shades of gray, Willard explains.

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Object Herbig-Haro 24 (HH 24), in the center of which is a protostar. 2015 year

Snapshot after processing

Photo taken with infrared channel

Also, the dynamic range — the difference between light and shadow — of the faintest nebula — is a million to one.The dynamic range of a studio portrait is 3: 1, ink on paper can render at best 20: 1. To solve this problem and even out the contrast, scientists need to process the bright, medium and dark elements of the image before starting to paint.

All these elements – light, color and shadow – are woven together into one canvas through many layers in the usual “Photoshop”. Layer by layer, radiation noise is removed, too bright pixels are cut off, histograms are smoothed. But even with Photoshop it can take weeks to process a single Hubble image.

“We pay great attention to different cameras, different filters and different shutter speeds. We make great efforts to create an image that is both aesthetic and informative at the same time. Which will tell you something new about the Universe that you couldn’t even have before. think, “Willard describes his team’s work.

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Spiral galaxies NGC 4302 and NGC 4298 in the Coma constellation. 2017 year

Snapshot after processing

Snapshot with Wide-angle camera 3

What’s in your name

It is interesting that if the image processing can take weeks, then coming up with a name for a space object sometimes takes only half an hour.

That’s how long it took to come up with the name “Bat’s Shadow” – the huge shadow cast by HBC 672, Willard recalls.

“We are like children looking at the clouds in the sky: this is an elephant and this is a giraffe,” Willard says. And he’s joking: the Russians were the first to take pictures of the far side of the moon and come up with names for objects on its surface – the Sea of ​​Moscow, the Mendeleev crater. “It was humiliating, we had to catch up,” he laughs at the name that American researchers have come up with for another of the objects filmed by Hubble – Gomez’s Hamburger.

Meanwhile, anyone can not only look at the images of the Universe – he can create them himself. Only relatively few Hubble images are professionally processed – most remain in black and white data in NASA archives awaiting decryption. These archives are in the public domain.

All photos – NASA / STScI.

Closer to the stars: how observatories work

It is difficult to name the exact time of the appearance of the first observatories.The structures where the celestial bodies were observed were built in ancient Assyria, Babylon, China, Egypt, Persia, India, Mexico, Peru. Today there are more than 500 observatories in the world: the press service of the Glavgosexpertiza of Russia has chosen the most interesting of them.

The first astronomers were the priests – they were the ones who observed the starry sky. And the beginning of these observations was laid back in the Neolithic and in the Bronze Age – it was then that one of the first observatories, Stonehenge, was created, located 130 km from modern London.The megalithic temple of Stonehenge was a sacred place of the ancient Celtic priests of the Druids – and they were well versed in the structure and movement of stars, knew the size of the Earth and the planets of the solar system, and studied astronomical phenomena. Stonehenge was founded in the XXX century BC. Another ancient observatory – it is five thousand years old – was discovered on the territory of Armenia.

The first observatory in the modern sense of the word was the Alexandria Museion, founded at the beginning of the 3rd century BC.e. under Ptolemy Soter on the initiative of Demetrius of Phaler. Museion was a religious, research, educational and cultural center of the Hellenistic era. It also included the legendary Library of Alexandria, which, according to some sources, contained up to 900,000 scrolls. It was at the Alexandria Observatory that high-precision instruments such as gnomons and quadrants began to be used for the first time. And the scientist Hipparchus invented the astrolabe based on the principle of stereographic projection.

Modern observatories began to be built in Europe in the 17th century after the telescope was invented.In 1667, a large state observatory was opened in Paris. Along with the instruments of ancient astronomy, large refractive telescopes have already been used here. In 1675 the Royal Greenwich Observatory on the outskirts of London was opened.

In 1692, the first Russian observatory was founded in Kholmogory by the priest Afanasy Lyubimov. In 1701, by order of Peter I, an observatory was created at the Navigation School in Moscow. Founded in 1839, the Pulkovo Observatory was equipped with the most advanced instruments, which made it possible to obtain high-precision results.For this, Pulkovo Observatory was named the astronomical capital of the world, and to this day it remains the main one among twenty Russian observatories.

The buildings of modern optical observatories are built in a cylindrical or multifaceted form: these are towers in which telescopes are installed. The weight of the optical device can reach several hundred tons, and it is driven by motor systems. For inspection and repair, parts of the telescope are removed using a crane. The multilayer dome of the observatory is made of steel and equipped with shutters moving along rails.The building of the observatory necessarily includes an air conditioning system for cooling the dome and computers, as well as offices of scientists, elevators, wide main gates, allowing the delivery of bulky equipment.

Observatories are usually located far from cities, in areas with low clouds and illumination, if possible on high plateaus, where atmospheric turbulence is insignificant and infrared radiation absorbed by the lower atmosphere can be studied.

There are specialized observatories that work according to a narrow scientific program – radio astronomy or mountain stations for observing the Sun. There are observatories on board spaceships and on orbital stations. For example, the TESS spacecraft has discovered more than 2,100 planets in two years of operation.

Six of the world’s largest observatories

China Astronomical Observatory or Celestial Eye (FAST)

The world’s largest astronomical observatory is located in the southwest of China.Out of 400 other locations, a mountain valley was chosen, located at an altitude of almost a kilometer above sea level – it is ideally suited for its size and level of protection against radio frequency waves. The remote area, however, complicated the task for the builders, who had to live in a mountain gorge far from civilization, where at first there was no electricity. Construction began in 2011 and took five years. As a result, the largest spherical radio telescope on the planet was built, which is a 500-meter dish of 4400 aluminum panels.The observatory cost the state $ 180 million. The Chinese radio telescope stores an incredibly large amount of data and is capable of detecting even the faintest radio waves emanating from celestial objects, including pulsars and entire galaxies.

Paranal Observatory (VLT), Chile

This is a whole system of four main antennas with a diameter of 8.2 m and four auxiliary antennas of 1.8 m each, combined into an astronomical interferometer.Scientists from the European Southern Observatory work here. The facility is located in the highlands of the Andes at an altitude of more than 2.5 km above sea level in the Chilean Atacama Desert. This arrangement of the telescope gives a great advantage: the sky in this area is cloudless almost all year round, which allows observations to be carried out continuously, in addition, the rarefied atmosphere allows avoiding distortions created by the movement of air masses. Therefore, the observatory receives a signal in the optical and mid-infrared ranges, and processes the material received by a supercomputer capable of performing up to seventeen quadrillion operations per second.

Arecibo, Puerto Rico

Arecibo Astronomical Observatory is located in Puerto Rico at an altitude of 497 meters above sea level. Cornell University and the US National Center for Astronomy and Ionosphere are conducting research here. The diameter of the dish of the radio telescope is 304.8 m, and the depth of the mirror is 50.9 m. The surface of the reflector is covered with 38 778 aluminum plates, each of which has a size of 1×2 meters.The mirror itself is located in a natural depression, and the movable feed is suspended on cables from three support trusses: its position determines which part of the sky will be in focus. Interestingly, the telescope reflector, transparent to sunlight, is used as a greenhouse for growing crops. The radio telescope is necessary for research in the field of radio astronomy, atmospheric physics and radar observations of objects in the solar system.

Roque de los Muchachos Observatory or Large Canary Telescope (GTC)

The observatory is located on the Canary Island of Palma at the peak of the extinct volcano Muchachos at an altitude of about 2400 m above sea level.Along with the observatory in Chile, this observatory is one of the best places on Earth in terms of astroclimate. In 2007, the Great Canary Telescope was commissioned – an optical reflector telescope with the largest mirror in the world. Its primary hexagonal mirror, with an equivalent diameter of 10.4 meters, is composed of 36 hexagonal segments. The telescope is equipped with active and adaptive optics and is able to see objects a billion times fainter in light than those that are visible to the naked eye.

Keck Observatory, USA

The observatory is located at the peak of Mount Mauna Kea (Hawaii) at an altitude of 4145 meters above sea level.From 1993 to 2007 – until the introduction of the Large Canary Telescope GTC (10.4 m) – the observatory’s telescopes were the largest in the world. Two mirror telescopes with hexagonal mirrors 10 meters in diameter. And it was here that the largest number of exoplanets was discovered.

Special Astrophysical Observatory, Russian Academy of Sciences, Russia

In Russia, the largest telescope is installed in a special astrophysical observatory in the Republic of Karachay-Cherkessia in the North Caucasus.It is mounted at an altitude of just over 2000 meters above sea level. The main reflector mirror is 6 meters in diameter. Until 1993, it remained the largest in the world, until the Keck Observatory was built. Today, the telescope is planned to be modernized – the main mirror has been dismantled and sent to the manufacturing plant for re-polishing, and new electronic equipment for the tracking and guidance system will be installed here.

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Responses | § 17. Investigation of the electromagnetic radiation of celestial bodies – Astronomy, 11 class

1. What ranges is the entire spectrum of electromagnetic radiation subdivided into?

Gamma radiation, X-rays, ultraviolet, visible rays, infrared and radio waves.

2. Why is it impossible to study celestial objects from the surface of the Earth in all ranges of electromagnetic radiation?

Because the Earth’s atmosphere transmits radiation only in certain wavelength ranges: from 300 to 1000 nm, from 1 cm to 20 m, and in several “windows” of the infrared range.

3. What are the main tasks in astronomy with the help of telescopes?

1. Collect as much radiation energy of a certain range of electromagnetic waves from the investigated object as possible;
2. Create the sharpest possible image of the object, so that you can highlight the radiation from its individual points, as well as measure the angular distances between them.

4. How can you determine the apparent magnification of the telescope optical system?

Find the ratio of the angle at which the image is observed to the angular size of the object when viewed directly with the eye.

5. What is meant by the resolution of a telescope? Permeable ability?

Resolution is the smallest angular distance between two stars that can be seen separately through a telescope. Permeability is the limiting stellar magnitude of a luminary accessible to observation with this telescope under ideal atmospheric conditions.

6. What is meant by extra-atmospheric astronomy?

Extra-atmospheric astronomy studies celestial objects using equipment located outside the atmosphere (in space) in order to capture certain ranges.

7. What is the difference: optical telescopes from radio telescopes; a radio interferometer from a radio telescope?

Radio telescopes consists of an antenna device and a sensitive receiving system. Used to detect and receive cosmic radio emission. Optical telescopes are designed to receive optical radiation.

The radio interferometer combines several radio telescopes. The radio interferometer summarizes the obtained images to increase the resolving power of the telescopes.

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90,000 Astronomers have found a new unusual category of potentially habitable exoplanets

British astronomers have identified a new category of relatively large exoplanets – mini-neptunes, very different from Earth, but capable of supporting the existence of life. This could significantly increase the number of potentially habitable places outside the solar system.

Earlier, in their search for life, astronomers paid attention primarily to planets similar to Earth – with approximately the same size, mass, temperature and atmospheric composition. However, scientists at the Cambridge Institute of Astronomy believe that in doing so they have always overlooked much more promising opportunities. An article about this was published in the Astrophysical Journal, the preprint is posted on the site arXiv.org .

A new category of potentially habitable planets is proposed to be called Hycean – “highkeans”.These are hot, ocean-covered planets with a hydrogen-rich atmosphere, which are much more common in the Galaxy than terrestrial planets. Previously, they were usually referred to as super-earths or mini-neptunes.

“Such planets open up completely new opportunities for the search for life in other worlds,” says Nikku Madhusudhan of the Cambridge Institute of Astronomy, who led this research.

Many of the main candidates for “highkeans” selected by British astronomers are larger and hotter than Earth, but still have characteristics that allow them to have large oceans that are capable of supporting microbial life, similar to that found in some terrestrial aquatic ecosystems with extreme conditions.The advantage of such planets is that they form near their stars a much wider potentially habitable zone, or, as they say, the “Goldilocks zone”, in comparison with the terrestrial planets. This means that they are still capable of supporting life even where planets like Earth are already clearly out of this range.

The first exoplanet was identified almost thirty years ago, and since then 4.5 thousand new planets have been discovered outside the solar system.The overwhelming majority of them in size are between the Earth and Neptune, and they are considered super-earths or mini-neptunes depending on their size and composition: they can be predominantly rocky or, conversely, ice giants with an atmosphere saturated with hydrogen. Sometimes there is something in between.

Most mini-Neptunes are at least 1.6 times larger than Earth, but significantly smaller than Neptune. They are too large to have a hard rocky surface, like Earth, and previous studies of such planets have shown that the pressure and temperatures under their hydrogen envelope are too high to talk about the existence of life similar to Earth.

However, a recent study of mini-neptune K2-18b by Madhusudhan’s team showed that under certain conditions these planets can still support life. A red dwarf exoplanet, 124 light years from Earth, orbits its star in 33 days and contains water in its atmosphere. Its diameter is 2.6 times that of Earth, and its mass is 8.6 times that of Earth, in fact, it is a cross between a super-Earth and a mini-Neptune. This study prompted scientists to re-examine the full range of properties of planets and their stars, satisfying conditions suitable for life, in order to consider the possibility of observing characteristic biomarkers – chemical traces in atmospheres that indicate the existence of life.Most often these are oxygen, ozone, methane and nitrogen oxide N ₂ O, which are also present on Earth. There are also a number of other biomarkers, such as methyl chloride and dimethyl sulfide, of which there are significantly fewer on Earth, but they can also serve as promising indicators of life on planets with a hydrogen-rich atmosphere where oxygen and ozone are low.

According to British scientists, planets that are 2.3-2.6 times larger than Earth and weigh 5-10 Earth masses can still have oceans covering their entire surface under a hydrogen atmosphere, whose temperature is about 200 ° C.Moreover, conditions in such oceans may be similar to those that allow microbial life to exist in Earth’s oceans. Exoplanets, on which life can exist, also include planets very close to their stars and gravitationally locked due to tidal interactions, always turned to the star with one side. These are the “dark” worlds among the “highkeans”, where life is possible only on the night side.

In the known population of exoplanets, planets of just such sizes and types predominate, but until now they have received much less attention than super-earths.The prevalence of “highkeans” in the Universe means that the most promising places for the search for life in other parts of the Galaxy could be hidden in plain sight.

“Basically, when we were looking for these different molecular signatures, we were focusing on planets like Earth, which seemed quite reasonable to start the search,” Madhusudhan says.”However, now we think that highkean planets give us a better chance of finding multiple biomarkers at once.”

Madhusudhan and his team suggest that a number of terrestrial biomarkers can be easily found in the atmospheres of “highkeans” using spectroscopic observations in the very near future. The larger sizes, higher temperatures and hydrogen-rich atmospheres of such planets make their atmospheric biomarkers much more visible than those of terrestrial planets.

“The discovery of biomarkers will change our understanding of life in the universe,” Madhusudhan explains.“We need to be open about where we expect to find life and what form it can take, as nature continues to amaze us in often the most unimaginable ways.”

The Cambridge Group has unveiled a large sample of planets that could be early candidates for exploration with next-generation telescopes such as the James Webb Space Telescope. Its launch is scheduled for the end of this year. All planets selected in this way revolve around red dwarfs at distances of 35-150 light years from Earth, which is very close in astronomical scales.Already planned follow-ups for the most promising candidate, K2-18b, may lead to the discovery of one or more biomarkers.

90,000 The origin of everything: why life appeared on Earth

How everything appeared everywhere: stars and galaxies, the Earth’s atmosphere, oceans, cells and, finally, human civilizations. Combining humor and a scientific canvas, the author guides readers through space and time – almost 14 billion years – while showing the connections between theories, helping to understand topics such as particle physics, plate tectonics and photosynthesis.All this is about the book “The Origin of Everything” by David Berkovichi, translated by the publishing house “Alpina Non-Fiction”. Indicator.Ru publishes an excerpt from this book.

Unlike other planets of the solar system, a temperate climate was formed on Earth, therefore water in a liquid state was preserved on it, and therefore life, at least those forms that are known to us. The first living organisms that appeared on Earth were microorganisms, and this happened several billion years before the moment from which we, humans, consider the planet suitable for life, let alone hospitable.But even today, we have found microbial life on the planet that lives in the most unfavorable natural conditions – in environments where temperatures exceed 100 ° C, or in acid crater lakes. Therefore, the definition of “fit for life” has a fairly wide range. We can find microbial life that exists or once existed on other planets, the conditions on which are not worse than the worst conditions on Earth.

Water is extremely important for life, so the list of potentially habitable planets includes Mars and the icy moons of Jupiter and Saturn (Europa and Enceladus, respectively), which definitely have liquid water.Be that as it may, we know for sure that a particularly stable and mild climate has developed on our planet, which has given life enough time to become complex and multicellular. The conversation about the conditions necessary for the existence of life on the planet should begin with the classical concept of the “zone of possible life.” This zone is, in fact, the range of orbits in any planetary system where the conditions on the surface of the planets in it allow water to exist in a liquid state. In other words, the planet should not be so far from the star for all the water to freeze (as probably happened on Mars, although this is becoming increasingly doubtful), but not so close that all the water evaporates (as on Venus).This concept is still used today by astronomers discovering planets in other planetary systems, since the main characteristics they establish, at least for now, are the distance from the planet to the star and (sometimes) the mass and / or size of the planet.