Approximate distance from the ground to the nearest exoplanets. What are the planets of the earthly type? Classification and examples

Are we alone in the universe? Over this issue, humanity breaks the head for many centuries. Not so long ago it was believed that the Earth is the only planet in the Universe, where life exists, but now scientists are not so firmly convinced.

New technologies of spectrometric measurement of radial speeds of stars allowed scientists to take a look far beyond our Solar system And the data obtained confirmed their thoughts that the land is far from so unique, as it was previously thought. According to the latest NASA calculations within the Milky Way there are at least 200 billion stars and at least 10 to 20% of them may be inhabited worlds.

When exoplans were found for the first time

The first assumptions about the existence of land-like bodies that rotate around other celestial luminaries were made by the medieval scientists Copernicus and Jordano Bruno. But until 1995, official science considered existence similar to the Earth exoplanets of pure water speculation. Now, scientists were convinced that almost near each star had one or more planets, and this is already hundreds of millions of potentially inhabited worlds only within one of our galaxy.

Unfortunately, exoplanet detection technologies today are in its infancy, but NASA hopes to make a huge breakthrough in the next decade. The construction of powerful orbital telescopes should increase knowledge in many areas of astronomy and primarily in the search for inhabited worlds.

What is exoplanets and what are the types of exoplanet

The exoplanet is called any planet that is outside the solar system. They can have a different size and composition - from small rocky planets to huge gas giants. In total, there are currently 3,583 exoplans in 2688 planetary systems. Exists different methods Exoplanet classification, but according to the NASA standard, they are divided into the following types

Exo land. These are planets earth Groupwhich are similar to our mass, composition, radius, atmosphere and orbit in the inhabited zone of their stars. Basically, they consist of heavy elements, such as silicate breeds and metals. They have a metal core, silicate mantle and bark. Also they possess sufficient magnetic field, To preserve the atmosphere and protect the surface from excess radiation and star winds. Therefore, among the first candidates for the role of a new homeland for earthlings, precisely such exoplans, similar to Earth in all major parameters.

Supermeni. These are planets with a mass of 1-10 Earth. This term does not focus on the inhabitants and surface conditions. heavenly Body. They are denoted by all new exoplans of which exceeds the earthly, but does not reach the gas giants. They can be both completely unsuitable for habitat and have all the conditions for life.

Ocean planets and desert planets. These are exoplanets, which are either 100% covered with water in a liquid form, or, on the contrary, representing an absolutely dry desert without the slightest marks of water in any form.

Scientists believe that the chances of the birth of life within the limits of water worlds that are located in a stable orbit, high enough. The desert planets, in turn, are absolutely dead and can hardly serve as a new face for a person in the future.

Gaza giants. Gas giants are called all planets with masses exceeding the earth 10 times and a composition consisting of a small stony core, surrounded by hydrogen and helium. Almost all open exoplans found from the very beginning are precisely gas giantsBecause it is much easier to detect them than small terrestrial rocky planets.

Hot Jupiter. These are gas giants that rotate very close around their star. This is a kind of high-temperature version of the usual gas giant.

At first, they have become a complete surprise for scientists, since such bodies can only be formed in significant remoteness from the star where hydrogen compounds can fade into solid slices of ice. It was later proved that hot jupiters are ordinary gas giants who migrate to the center of their solar system, being captured by the gravity of the star.

Nomadic planets. Planets without a star freely floating throughout the galaxy. According to estimates, scientists the number of rogue planets in our galaxy is very high and calculated hundreds of billions, but it is difficult to detect them. Chances that life can exist on such a planet very small. In addition, they can be dangerous for other more hospitable worlds.

There are also hypothetical types of planets, such as chtonic and pulsary planets. The first are the former gas giants burned to the full loss of the gas shell, and the second are dead celestial bodies that turn around the pulsars.

The first studied exoplants suitable for life

KEPLER-62 F

According to many scientists, this planet is one of the most similar to Earth. She is 1.4 times more land and refers to the class of warm superemen. Her sun is a single orange dwarf in the constellation Lira Kepler-62 from 4 to 7 billion years. It is believed that with a lot of probability there is liquid water and an atmosphere with a predominance of carbon dioxide, so the planet is located in the seti target list. The only minus is the distance. Kepler-62 F is 1200 light years from us, so it is not possible to study it in detail in the foreseeable future.

Gliese 667 c C

If there are exoplants suitable for life, then Gliese 667 C C will definitely get into this list. Its pluses are a temperature regime, 90% similar to earth, the presence of a sufficiently dense atmosphere with a high CO2 content and relative proximity to Earth (22 light years). As the main minus, we can consider a mass that exceeds the earthly minimum. Therefore, future colonists will have to exist with elevated gravity. The planet rotates around the red dwarf glyze 667. His age is estimated at 4-7 billion years, and the mass is only 31% of the mass of the Sun.

KEPLER-62 E

Perspective superer, which rotates around KEPLER-62 star. Astronomers are confident that its mass is only 1.6 times higher than the earth, and 90% of its surface is covered. warm ocean. This planet resort, which has every chance of becoming a cozy home for various aquatic organisms (according to NASA calculations, the probability of this is up to 70-80%).

Gliese 581 G.

Another planet with the controversial status, the existence of which is confirmed, then again refutes. Presumably it is located near the star Glize 581 in the constellation of the scales, in 20.4 light years from the ground. Scientists who do not doubt its existence assure that in terms of the level of suitability for the population, it is one of the most attractive. Red dwarf should give enough heat so that this stony planet can exist their rivers, lakes and the sea. Therefore, studies around Gliese 581 G are still underway.

KEPLER-22 B

Perhaps the most famous and well-studied exoplanet. According to scientists, even in the case of their worst concerns, this planet will be suitable for a relatively comfortable life. Its radius is more than 2.4 times, therefore, the force of gravity in any case should be acceptable. It is also assumed to have an atmosphere with a high CO2 content and the presence of a large amount of water that covers everything with the exception of polar hats.

The sun of the planet - Kepler-22 is between the Constellations of the Swan and Lyra. It is similar to the earth's sun on the spectral class, and its radius and mass are 0.979 and 0.970 from the solar. In general, almost like at home. True, you will have to fly distant - 619 light years.

New exoplanets

The newest discovery of astronomers is a single star in the constellation Aquarius TrapPist-1, around which seven exoplanet rotates. This planetary system is removed from the Earth for 40 light years and on the unanimous opinion of scientists from NASA, its discovery is a grand luck. After all, according to preliminary estimates, all seven exoplanets are similar in size to Earth and at least three of them have liquid water. The star itself is a red dwarf of which is estimated at about 500 million years. And although the planets are located quite close to the luminary, its activity is relatively low, so the planets are unlikely to be analogues of our Venus.

Why is the discovery of Trappist-1 is so important? Scientists call several basic advantages of this planetary system before the rest. The first is the youth and stability of the sun. M-dwarfs live for a long time, and therefore, if the person there will ever get there, he will be guaranteed to catch all seven exoplanets. Second - hospitability. In the atmosphere of three of the seven planets there is oxygen, carbon dioxide and ozone, which implies reliable protection against solar radiation. The third - 40 light years is a relatively small distance. Therefore, the opening of exoplanets in the TRAPPIST-1 system is indeed extremely an important event, the significance of which is difficult to overestimate.

Proxima Centaurial B - the nearest exoplanet of the earth

The proxima Centaur B is the closest to the Earth exoplanet (4.22 light years) in the so-called dullness area. This factor is very important, since the rest of the exoplanets, similar to Earth are located in dozens and hundreds of light years from us. It is possible that the first attempts of the expedition to far cosmos will be sent precisely in this direction.

But not so everything is rosy, as it seems at first glance. Based on the available NASA data, the proximation of Centauri B is a cold stony super-earth, which gets a vag radiation radiation From his shining. Therefore, the first people who visit there can hardly be hoped on the hospitable reception. However, humanity still does not have effective means for long-range travel travel. This gives hope that by the time of the invention of the first interstellar ships, new and more promising exoplans will be found near us.

When it becomes possible to colonize the nearest exoplanets and which obstacles exist

The discovery of exoplanets is 100% suitable for settlement is only a half business. Even if there will be exoplants suitable in all parameters near the ground (1-10 light years), they still separate such gigantic distances from them that space expeditions still seem completely unreal.

At the moment there are already projects of space sailboats and thermonuclear missiles capable of leaving the limits of the solar system, however, their tests faced several serious difficulties. Basic - low efficiency. Even if ships achieved the planned speed, flight to the nearest star will take at least 10 years one way. Second - inevitable corps damage space dust Upon reaching high speeds. The third is the devastating load on the human body during acceleration or braking.

And this is no longer speaking for such dangers as the risk of radiation exposure of the crew during flight or possible psychological problems associated with such long-term finding in a closed space.

What can I count in the near future

Other promising developments, such as a photon engine on magnetic monopolides, an ion engine, a basin engine or annihilation engines in theory can be implemented in the coming decades and are able to provide sufficient performance to reduce the duration of flight to the same alpha centaurus or barnard star to 2- 5 years. But at the same time the second and third problem still remain open.

A good alternative could be instant movements with the help of the so-called " mobbo"Or warp engines, but at the moment all this applies more to the discharge of science fiction. The possibility of the existence of the first today is in question at all, and today, though have a theoretical substantiation (thanks to the work of Miguel Alcuberre physics), but no one even represents these principles in practice. Therefore, according to NASA, in the near century, the piloted expeditions beyond the limits of the solar system can not even dream, and the main program of colonization will be directed towards Mars and Jupiter satellites.

Is there a chance to detect life on well-known exoplanets? On this expense, scientists do not dare to make any accurate assumptions. Through the study of such extremal organisms as Himalayan spiders, marine deep-sea ringed and devilish worms, various deep-sea bacteria, BDELLOIDEA or low-speed bacteria, Biologists are trying to simulate the development of life forms on other planets, but it is still like moving blindly. The only thing that can be argued exactly - no meetings with representatives of highly developed civilizations in the near future can not be afraid. After all, despite all efforts, in the entire history of observation, no artificial signals were found, capable of indicating the alien mind. So, the probability of crossing up with other space travelers is striving for zero.

Dwarf planets like Ceres and Pluto, as well as other major asteroids look like the planets of the earth group by the fact that they have a solid surface. However, they consist more of ice materials than stone.

Earth Group

Most planets found outside the solar system were gas giants because they are detected easier. But since 2005, hundreds of potential exoplanets of the earth group were discovered - largely due to space Mission "Kepler." Most planets have become known as "Super" (that is, the planets with a mass between the ground and the neptune).

Examples exoplanets of the earth group, a planet with a mass of 7-9 Earth. This planet rotates around the Red Dwarf Gliese 876, located in 15 light years from the ground. The existence of three (or four) exoplanets of the Earth Group was also confirmed between 2007 and 2010 in the GLIESE 581 system, another red dwarf in about 20 light years from the ground.

The smallest of them, Gliese 581 E, by weight of only 1.9 Earth, but rotates too close to the star. The other two, Gliese 581 C and Gliese 581 D, as well as the estimated fourth planet Gliese 581 G, are more massive and rotate within the "" star. If this information is confirmed, the system will become interesting to the presence of potentially inhabitable planets of the earth type.

The first confirmed Exoplanet of the KEPLER-10B Earth Group - the planet weighing 3-4 terrestrial planet, located in 460 light years from the ground, was discovered in 2011 during the Kepler mission. In the same year, the Kepler Space Observatory has released a list of 1235 exoplanetic candidates, including six "supermenities" located within the potentially inhabitable zone of their star.

Since then, "Kepler" found hundreds of planets in size from the moon to big land, and even more candidates outside these sizes.

Scientists offered several categories to classify the planets of the earthly type. Silicate planets - This is the standard type of the planets of the earth group in the solar system, consisting mainly of silicate solid mantle and metallic (iron) kernel.

Iron planet - This is the theoretical type of the globe planets, which consists almost entirely of iron, which means a more dense and smaller radius than other planets comparable mass. The planets of this type are believed to be formed in high-temperature areas close to the star, where the protopatabre is rich in iron. Mercury can be an example of such a group: it was formed close to the Sun and possesses a metal core, which is equivalent to 60-70% of the planetary mass.

Planets without nucleus - Another theoretical type of globe planets: they consist of silicate rocks, but do not have a metal kernel. In other words, planets without a nucleus are the opposite of the iron planet. The planets without cores are believed to be formed further from the star, where the volatile oxidant is more common. And although we have no such planets, there is a mass of chondrites - asteroids.

Finally, is carbon planets (The so-called "diamond planets"), the theoretical class of planets, which consist of a metal kernel surrounded mainly by carbon minerals. Again, in the solar system there are no such planets, but there is an abundance of carbon-saturated asteroids.

Until recently, all the scientists knew about the planets - including their education and the availability of different types, it was out of studying our own solar system. But with the development of the study of exoplanets, which saw a powerful splash over the past ten years, our knowledge of the planets increased significantly.

On the one hand, we came to understand that the size and scale of the planets are much higher than they thought before. Moreover, we first saw many planets similar to Earth (which can also be inhabited) existing in other solar systems.

Who knows that we find when we get the opportunity to send probe and manned missions to other planets of the earth group?

NASA AMES / JPL-CALTECH / T. PYL Planet KEPLER-452B in the artist's representation

Astronomers have already found quite a lot of exoplanets, which are potentially vitally. In the new work, experts focused on the number of ultraviolet radiation emanating from the parent star and capable, as expected to contribute to the development of life: on this basis, the researchers identified the planets on which life could appear like life on our planet.

"Life, as we know, requires a lot of molecular structures that perform various functions inside the cell - explains the astrophysicist Paul Rimmer from Cambridge University. - including DNA, RNA, proteins and cell membraneswhich consist of relatively simple building blocks (lipids, nucleotides and amino acids). For a long time, where data from these building blocks came from, remained a mystery, but recently important discoveries helped determine how they appeared on the surface of the Earth. "

"For example, - explains Rimmer, - Ultraviolet highlighting sinyl Acid (Chemical compound, existing in nature) in water, in the presence of a negatively charged ion, such as bisulfite, leads to the appearance of simple sugars. " Under suitable conditions, blue acid - which in large quantities is contained in protoplanetary disks - and a negatively charged ion can produce huge concentrations of building blocks for life, but for this they need ultraviolet.

In 2015, researchers demonstrated this experimentally. So, with the help of UV radiation and blue acid, they managed to create lipids, amino acids and nucleotides, which are components of living cells, but without the use of ultraviolet the reaction did not take place.

Rimmer and other scientists used this data for a new study. Experts compared the amount of used UV radiation in the 2015 experiment with radiation emanating from stars in planets - Kepler candidates (potentially vital exoplanets detected by Kepler's space telescope). Based on the calculations, the researchers identified the so-called zone of abogenesis - the distance from the star, on which the planet would give enough UV radiation. (The list of candidates "Kepler" includes stony planets located in the dwelling area: not too close and not too far from the star - so that liquid water could exist on the planet.)

It is important, as noted that the star possessed the temperature similar to that in the Sun: then the inhabitancy zone and the zone of abogenesis intersect. Cooling stars usually emit UV radiation in insufficient quantities - if, of course, frequent flashes do not occur: whether the latter will be able to lead to the emergence of building blocks for life, as long as researchers noted, remains unknown.

Planet Kepler 452-B (due to the possible similarity with the Earth, it was called "Earth 2.0"), as experts were established, enters both in the habitability zone and in the Abiogenesis zone. In addition, according to researchers, the KEPLER-62E planet is likely to enter the Abiogenesis zone, but it may not be stony.

The Kepler telescope, found a lot of planets outside of our solar system, will soon stop working (in the device, as is known, fuel ends). However, the TSS Space Telescope has already been launched to replace it (it is officially officially

New York, August 25th. / Corr. TASS Alexey Kachalin. Astronomers discovered the planet nearest to our solar system (exoplanet), similar to earth and suitable for life. We are talking about proxima b, which turns around the star proxima Centaur. The main calculations of scientists are published on the website of the Nature magazine.

There is no exoplanet closer and can not be

A group under the leadership of the Anglad-Eskud Guillem from the University of Queen Mary in London came to the conclusion that we are talking About the closest planet suitable for the existence of organic life in one form or another. "The good news is that it is (planet) is close. However, the location next door is not just a pleasant moment, this is a good dream for astronomers who want to continue observation of the object," said Anshar Reinarans co-author.

"This is not just the closest out of the already open planets of the earthly type, but also probably the planet coming to us outside the solar system from the already open or which will be open. There is no star that is closer (than proximation of Centaution) to the solar system, respectively, the planet ( This star) is located closer to all to the solar system, "the Anglad Ekda explained.

Relatively similar to earth

Proxima B is located at a distance of just 4.2 light year From the solar system, or at a distance of 266 thousand times greater than between the land and the sun. Until now, the most close to us was considered to be planets appearing around the Star Trappist-1 (Red Dwarf). From the ground to it, 40 light years.

Proxima b reaches 1,3 masses of ours, makes the turn around his shine for 11.2 days. The distance between the planet and its star reaches only 5% distances between the land and the sun. However, the proxima of the Centaurus is much colder than our shine, therefore its relative proximity does not exclude the presence of water on the surface of the water in liquid form.

Scientists admit existence at the planet of the atmosphere and estimate the air temperature on its surface at 30-40 degrees. Without the atmosphere, this indicator would be 28.9-40 degrees below zero.

Unfavorable factor

However, along with favorable factors for proxima b there are adverse factors. Thus, researchers believe that the level of ultraviolet and radiation radiation, which is exposed to the planet, is 100 times stronger than on Earth.

Scientists consider it appropriate to "carry out additional studies of the celestial body using spectroscopy high resolution and direct observations in the coming decades, as well as through (unpilotous) expeditions in the coming centuries. "Previously, thanks to the information transferred to the Earth, Kepler telescope, in our galaxy - Milky Way - More than a thousand exoplanets included in the systems formed around hundreds of stars were opened. NASA expects that new data on them will be obtained using the James Webb telescope, which should go to orbit in 2018.

GJ 1132B in the artist's representation

Max Planck Society

Astronomers from Great Britain, Sweden, Germany and Italy for the first time discovered traces of the atmosphere for Earth's exoplanets. Although it is definitely not possible to establish its composition, according to the authors, its spectral characteristics are well described with a mixture of water and methane. Earlier, astronomers observed the atmosphere only at significantly larger objects - hot jupiters. GJ 1132B has a mass of 1.6 times more earthly, and its radius exceeds the radius of the Earth 1.4 times. Research Posted by B. The Astronomical Journal, briefly about him press release of the Max Planck Society.

To date, about three thousand exoplanets are open. Most of them are gigantic objects with masses, the order of the mass of Jupiter and more. But in terms of the possibility of the life of life, the planets of terrestrial type are, which are much more difficult to detect.

There are two basic methods of search for exoplanets - on the Doppler shift and transit method. The first one is based on the fact that the gravity of the exoplanets causes the star to change its speed when rotating, from the point of view of the earth observer, it moves faster, then slower. This affects the position of the spectral lines of the shone. The second method is based on the fact that the exoplanet passes in front of the disk of the star, its luminosity decreases. Only the second method allows you to determine the characteristic dimensions of the planet and learn something about its atmosphere.

In the case of small planets, the study of the atmosphere is limited to the resolution of the telescope. Observations with the help of "Hubble" still not reliably detect any pronounced spectral features at the atmosphere of exoplanet of the earth type.

The authors of the new work chose a transit exoplanet of the earthly type as an object of study, located relatively close - in 39 light years from the ground. It addresses near Red Dwarf GJ 1132, located in the constellation of the sail. The planet was opened relatively recently - two years ago, and, according to the discovers, may have an atmosphere. At the same time, the equilibrium temperature of its surface is 600 Kelvin, so it is not suitable for life.

Visible radius of exoplanets in different spectral ranges

John Southworth et al. / The Astronomical Journal, 2017

Researchers conducted detailed observations of nine transits of exoplanets in front of the stars disk using a 2.2-meter telescope in the Southern European Observatory (Chile). Each transit astronomer was analyzed immediately in seven different spectral ranges: four optical and three infrared. For each range, the researchers estimated the visible diameter of the exoplanets.

It turned out that the visible diameter in one of the infrared bands with the statistical significance of four sigma exceeds the diameter derived from optical observations. According to the authors, it speaks of confident detection of the atmosphere of exoplanets. Astronomers note that the opacity of the atmosphere for infrared radiation can be explained by the presence of water, methane or other substances in it.

Astronomers note that the detection of the atmosphere in red dwarf is an important result. Many studies that red dwarfs are too active and outbreaks on their surface can completely fit the atmosphere of exoplanet, making them unsuitable for life. GJ 1132B acts as a counterpread for such statements. The planet is located just two million kilometers from the star, and its period of circulation is 1.6 days.

Red dwarfs include stars and, in the inhabited zones of which exoplanets of the earthly type were recently discovered. The possibility of living on them to scientists.

Vladimir Korolev