Every year more and more resources and specialists are involved in space exploration and solving its mysteries. Now scientists are looking for another life more actively than ever. Among the mass of cosmic bodies, the attention of the astronomer was captured by an exoplanet - it is she who acts as the hope of scientists for the origin and development of extraterrestrial life forms. To understand why such an object is worth studying, it is worth examining what this body is.

What is it?

An exoplanet is a planet outside the solar system. At the end of the 80s of the last century, the first such objects were opened.
As of the beginning of autumn 2019, 4 115 tel. At the same time, almost 2.5 thousand apply for this title, but for this they will have to re-register with the help of telescopes located on Earth.
All objects are found in a tenth of the studied stars, which are observed within the framework of the corresponding program. The number increases as data accumulates and as search and exploration tools evolve. Initially, the vast majority of discovered exoplanets were gas giants. However, later on, objects with lower masses were discovered.


Classification of gas giants

The subdivision of giant exoplanets was proposed by astrophysicist D. Sudarsky and expressed taking into account three factors that determine the atmosphere - temperature, appearance and features. There are 5 categories:

water clouds. The temperature does not exceed minus 20 degrees Celsius. Clouds contain: water suspension, methane, hydrogen. Despite the initial definition, it is problematic to classify such planets as suitable for life - these are only gas giants, which are removed from their own luminary in about the same way as the Earth is from the Sun;
ammonia clouds. The temperature does not exceed minus 1200 C. They are located at a great distance from the sun. Similar to Jupiter or Saturn;
silicon clouds. Temperatures over 1,100 degrees Celsius. Clouds are composed of silicates and iron vapor, which means they are highly reflective. Located close to the luminary;

cloudless. Temperatures range from 80 to 540 Celsius. Free from clouds, which means it has a low reflectivity;
with strong spectral lines of alkali metals. Temperatures range from 600 to 1,000 degrees Celsius. The atmosphere is composed primarily of carbon dioxide and alkali metal vapors;
The subdivision can be carried out according to other parameters. So, a separate terrestrial exoplanet is singled out, as which is recognized as a celestial object with the following characteristics:
does not consist of hot gases;
smaller than gas giants.
There are currently 200 known such planets.


Earth-like exoplanet with atmosphere

In the spring of 2017, European astronomers for the first time in history identified a planet outside our terrestrial system with signs of an atmosphere - this is GJ 1132b, located at a distance of 39 s. years from Earth. Its characteristics:

radius is 20% larger than earth;
mass 1.6 earth;
the surface is hard and rocky;
the composition of the surface is assumed to be similar to the composition of terrestrial rocks;
atmosphere is a mixture of methane and water vapor;
temperature - about 260 C.
Despite the high temperature and atmosphere, the discovery of a body so similar to that of the earth was recognized as one of the most important events at the moment and it is the most similar to our planet.

How does the search work?

An exoplanet is usually detected and recorded by several methods, since some of the available options only work under a number of specific conditions. The most commonly used techniques are:

direct observation. It is mainly used to highlight planets near young stars at a distance of no more than 10-100 astronomical units. The bottom line is that when an exoplanet is isolated from the light of its luminary, the observer can get a direct image of the celestial body;
Doppler. Revealing the radial velocity of a star using a spectrometer. With its help, it is possible to detect giant planets with a period of up to ten years and objects with a mass several times the mass of the Earth, which are located in the immediate vicinity of their sun. The mechanism is based on the interaction of the planet and the star: the planet, when the star rotates, contributes to its "wobble", which makes it possible to track the Doppler shift;
astronomical. Based on the correction of the proper motion of the star under the influence of the gravity of a celestial body. Helps with mass clarification;
transit. With its help, it is possible to obtain data on the size of the planet, the presence of the atmosphere and its composition by observing a decrease in the degree of luminosity of a star when an object passes against its background. In combination with the Doppler method, you can also find out the density of a celestial body. Relevant only in a situation when the orbit of the planet is located in the same plane with the observation point;
radio observation of pulsars. When planets revolve around a pulsar, the pulsar signal changes to an oscillating character - radiation forms conical surfaces in space;


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