The American aerospace agency NASA reported that in the constellation Aquarius there is a system of seven planets approximately the size of the Earth. On three of them, the conditions are suitable for the existence various forms life. This statement was made on emergency press conference dedicated to exoplanets beyond solar system.
Information was heard at the conference that seven years ago a group of scientists led by Michael Gillon began searching for exoplanets using the method of transits near faint stars neighboring the Sun. To do this, they used the 60-cm TRAPPIST robotic telescope in Chile. Last year, scientists announced the discovery of three Earth-like planets around the ultracold dwarf TRAPPIST-1, 39 light years away from the Sun.
Having made additional observations of this system with other ground-based telescopes, as well as with the help of space observatory Spitzer, they determined that a planetary system had been found near TRAPPIST-1.
We are taking a giant step forward with this discovery. It was previously believed that there were only three exoplanets around the star TRAPPIST-1, said Thomas Zurbuchen, head of the agency's science directorate.
Astronomer Scientific Institute space telescope in Baltimore, Nicole Lewis reported that three of the seven planets are in habitable zone. One of these planets is similar in size to Earth and has a similar temperature.
Note that earlier, a few hours before the start of the press conference former employee NASA Keith Cowing reported that TRAPPIST-1E, TRAPPIST-1G and TRAPPIST-1F are close in their characteristics to the planets of the solar system. The mass of exoplanets is from 41 to 134 percent of the mass of the Earth, the orbital period is 1.51 - 20 days. It is assumed that in addition to the size of the discovered exoplanets, according to at least six of them have a similar composition: they consist of stone minerals and at surface temperatures from 0 to 100 degrees Celsius can contain liquid water. Primarily we are talking about the planet TRAPPIST-1F, where the orbital period lasts nine days.
Since these exotic planets are located at a distance of about 39 light years, the inhabitants of the Earth will not be able to visit them in the near future.
In order to reach them by plane, it will take millions of years, - joked astronomer of the University of Liege (Belgium) Michael Gillon.
Scientists have said they intend to continue their study of exoplanets, and with the launch of the James Webb Space Telescope, they will be able to study the atmosphere and composition of these and similar planets.
By the way
In the spring of 2015, astrophysicists at the Zelenchuk Observatory in Karachay-Cherkessia tracked an unusual radio signal from the HD164595 star system in the constellation Hercules. After a year of observations, they came to the conclusion that the "alien" signal is of terrestrial origin.
A day after an extraordinary NASA press conference, at which representatives of the American space agency announced new Earth-like planets (not a word, by the way, without mentioning huge contribution European telescopes), we decided to write in detail about this event, if possible without using the words "sensation" or "for the first time in the history of mankind." Still, this discovery is not as grandiose as registration gravitational waves last year though big step forward - primarily in understanding the processes of formation of planets in stars different type, studying chemical composition planetary systems, comparing the characteristics of our solar system and more and more discovered systems in other stars. So four new planets around the star TRAPPIST-1 is really an excuse to hold an emergency press conference and even start your own website.
NASA has already released a poster calling for travel to newly discovered exoplanets
So what happened? In short, the red dwarf 2MASS J23062928-0502285 (its second name TRAPPIST-1) was found to have 4 new exoplanets resembling Earth or Mars in size, density and estimated surface temperature. Now let's explain each word of this sentence.
Where does the double name of the star come from?
Why does the star have two names and how is it correct: 2MASS J23062928-0502285 or TRAPPIST-1? The fact is that according to modern rules, the name of an object is assigned by the name of the telescope or the observation program that discovered it. The star from the constellation Aquarius was discovered during the 2MASS All-Sky Survey in the late 1990s. It was identified as an unremarkable red dwarf of spectral type M8 - there are now more than 500 million similar objects in the 2MASS catalog - and was not disturbed again for several years. Until 2015, long-term observations with the TRAPPIST telescope led to the discovery of three planets orbiting this star. After that, in order to distinguish it from millions of similar ones, it was given an additional name - TRAPPIST-1, that is, the first star with exoplanets discovered by this telescope.
What the strange name at the telescope? This, of course, is a science-intensive abbreviation, which stands for Transiting Planets and Planetesimals Small Telescope, that is, “Small telescope for searching for transit planets and planetesimals”, but the Belgians, who installed it at the La Silla Observatory in Chile, do not hide that it is also a homage to the famous monastery ale, which has long been brewed in their country. This telescope, by the way, is quite small, the diameter of its main mirror is only 60 centimeters, the same as, for example, at the Mayaki observation station near Odessa. It was built according to the Ritchie-Chrétien scheme (like the Hubble or Spitzer telescopes) - this allows it to take pictures of large sections of the sky without distortion (for example, the entire surface of the Moon at a time). In addition, the presence of only two reflective surfaces practically does not attenuate light and makes it possible to observe even very dim objects (at least four reflective or refracting surfaces are installed in the Schmidt or Maksutov telescopes popular with amateur astronomers). This is important because the main purpose of the TRAPPIST telescope is to search for comets, exoplanets, and observe small bodies of the solar system (for example, the telescope studied the dwarf planets Eris and Makemake). This robotic telescope is controlled directly from the University of Liege in Belgium, and if you are reading this news during the day in Russia, then for sure at this very time in Chile he continues to look for new exoplanets, and you can even live as he does.
The TRAPPIST telescope that made it possible to detect the first exoplanets around the red dwarf 2MASS J23062928-0502285
What is a transit method?
How were the first three bodies discovered around the star TRAPPIST-1? The transit method, which is used by most exoplanet hunters, such as the Kepler telescope. The method consists in tracking the apparent brightness of the star (since it is not known in advance which star has planets, telescopes with a wide viewing angle, such as TRAPPIST, are best suited here). If a star has a planet and the plane of its orbit is parallel to the line of sight of the telescope (that is, we see the orbit “edge-on”), then sooner or later, as it orbits, the planet will cover part of the star and for us it will become a little dimmer. It is still the most productive method: as of February 24, 2017, 2707 out of 3453 exoplanets have been discovered with its help. But he also has his shortcomings. In addition to the already mentioned limitation on the inclination of the orbit, it does not allow one to determine many important parameters, for example, the elongation of the orbit. In addition, if the exoplanet is far from the star (and therefore moves slowly in orbit), then the telescope must follow this section of the sky for a very long time to notice it. If aliens suddenly try to detect all nine planets in the solar system, then they will have to follow us for at least 160 years, and still this will give them only one signal from Neptune.
Simple in words, the method requires very careful observations, as well as algorithms to filter out changes in the star's apparent brightness that are not related to exoplanets (for example, caused by turbulence in the Earth's atmosphere).
However, in the case of the TRAPPIST-1 system, this did not become a hindrance - observations made since 2013 made it possible to register numerous periodic changes in the star's brightness, which could not be caused by any other reasons than the passage of exoplanets across its disk. According to the research results, a release of the European Space Agency was published in 2016, and we are in detail about it. It seemed that this was all, and this star was no longer fraught with new surprises, until four days ago there was a message about an emergency NASA press conference.
How have new exoplanets been discovered?
How can four new exoplanets be detected at once from a seemingly already well-studied star? The fact is that after the discovery of the first three planets, a team of astronomers led by Michael Gillon received observation time at the Very Large Telescope in Chile (yes, that’s what it is called: Very Large Telescope) and already after the publication of the article in 2016, they found that the signal that they initially took for the passage of the planet TRAPPIST-1d (each new discovered planet receives the name of the host star and the next unoccupied letter Latin alphabet starting with "b"), is actually a superposition of signals from three planets at once. This was so unexpected for the scientific community that the team was given observation time at several of the world's largest telescopes, including 20 days (that's a lot!) of continuous use of the Spitzer Space Telescope. The work of giants such as the 2m Liverpool Telescope on Palm Island, the 3.8m UKIRT Telescope in Hawaii, and the 4m William Herschel Telescope in the Canary Islands, together with a number of smaller overshadowing her. But it was precisely 20 days of Spitzer's work in September 2016 that gave 34 new signals that made it possible to unmistakably establish the existence of three new planets - there were six of them in total. Moreover, the initial superposition of signals was not accidental - the orbits of these planets are in resonance. This means that the rotation time of two neighboring planets is related as two integers: 8/5 for the first two planets, 5/3 for the second and third, 3/2, 3/2 and 4/3 for the next three pairs.
Exoplanets of the TRAPPIST-1 system (top row) compared to planets in the solar system (bottom row)
These patterns, as the authors note, indicate that the planets most likely formed in a single gas and dust cloud on b about further away from the star and gradually, losing angular momentum, migrated to near orbits. Similar theories were put forward more than a decade ago, they are now well developed, and the observations in the TRAPPIST-1 system are in excellent agreement with the predictions. Something similar, for example, should have happened with the moons of Jupiter - and Michael Gillon emphasizes in the article that the mass of TRAPPIST-1 is the same more mass of all the planets, how much Jupiter is greater than the mass of all its satellites. Indeed, Europa, Io, Callisto, and Ganymede are also thought to have formed from the flat disk of dust and gas that surrounded young Jupiter. Thus, the study of a gas giant located in our solar system, and a planet located 40 light years away, will help clarify the fundamental laws of the formation of celestial bodies.
Separately, it should be said that Spitzer saw another signal - once for 75 minutes TRAPPIST-1 became dimmer by 0.35 percent, and no already known planets could be the reason for this. According to astrophysicists, this indicates the presence of another, seventh planet. At the time of the press conference, none of the telescopes involved could register a second-pass signal, so the parameters of the orbit and the planet have to be judged precisely by these two numbers - the eclipse time gives the speed of the planet in orbit (and, as follows from Kepler's laws, the radius of the orbit ), and the decrease in the apparent brightness of the star helps to roughly establish the size of this seventh planet.
What are new exoplanets made of?
Now, having learned the number of planets, their orbits and approximate radii, is it possible to say something about the composition of the planets - what do they consist of, is there water on them? To do this, you need to know the mass of each planet. Above, we said that it is not possible to directly determine its transit method. However, with the TRAPPIST-1 system, we were lucky: all of its planets are located so close to each other (all of their orbits lie much closer to the star than the orbit of Mercury to the Sun) that they interact with each other gravitationally, either speeding up or slowing down their movement along the orbits. This was manifested in the fact that each planet eclipses the star for different periods of time. During observations, the difference in the passage of the same planet across the disk of a star reached 30 minutes. This is for orbits that, in the absence of perturbations, remain unchanged for billions of years! Such transit time variations have helped scientists build analytical and numerical solutions and calculate the most probable masses of the planets. The reliability of these methods strongly depends on the number of measurements, therefore, as new signals are accumulated, the mass values will be refined, but so far they are all in the range from half to one and a half Earth masses.
Comparison of the orbital sizes of the Jovian moons, the TRAPPIST-1 system and the solar system (it is not to scale with the others, and therefore it is not clear that all the discovered exoplanets would be comfortably located inside the orbit of Mercury).
NASA/JPL-Caltech
Knowing the mass and size of the planet, you can calculate its density, which means you can talk about what it is made of. It is clear that the errors here are large, but it seems that the density of five planets differs from that of the Earth by no more than 20 percent. This means that they must be rocky and probably contain water. Water is not as exotic a compound as it might seem - it was found on the surface of comets and asteroids that came to us from the outskirts of the solar system. Therefore, it may well be part of the planets, which, as we remember, were formed at a distance from the TRAPPIST-1 star. We currently do not have evidence of the existence of water on these planets, but I would like to warn the reader against unreasonable skepticism: the hypotheses of scientists are not taken from the ceiling, but are built based on the results of using models with many input parameters. For example, the ability of planets to reflect and re-emit the light incident on them from a star was measured - this also indirectly indicates the composition of the planet and the presence of an atmosphere on it.
Comparison of the densities of the discovered exoplanets (colored dots) with the densities of the Solar System planets (gray dots). The radius of the planets is plotted vertically, their masses are plotted horizontally. It can be seen that the TRAPPIST-1 planets can have a structure similar to Earth, Venus or Mars. However, it is worth paying attention to the measurement error (horizontal colored lines) - they are very significant and do not allow us to confidently speak about the composition of the planets.
Michael Gillon et al, 2017
Now let's talk about the climate. The uniqueness of the system is that six, and maybe all seven planets fall into the habitable zone - the conditional range of distances from the star, at which it warms the planet so that unfrozen water can exist there. Most likely, all the planets experienced tidal capture by TRAPPIST-1, that is, they make one revolution around their axis simultaneously with the revolution around the star. This means that, like the Moon to the Earth, they are always turned to it on one side, on which the temperature is always higher than on the other, dark side. Theoretical calculations performed by various exoplanet research groups suggest that this should not be a hindrance to the existence of liquid water, - if available enough dense atmosphere, tectonic activity and a single ocean, heat will be effectively transferred to dark side planets without creating strong temperature fluctuations.
Department Professor theoretical mechanics MIPT Vladislav Viktorovich Sidorenko explains how this can happen: “The fact that the orbits of the planets in TRAPPIST-1 have small radii contributes to gravitational capture - the establishment of such a mode of motion when the planet is turned to the star by the same side. In this case, the tidal deformations of the planet are determined by the eccentricity of its orbit. And although the eccentricities of the planets in TRAPPIST-1 are small, in combination with a close position to the star, powerful tidal deformations occur, which can lead to the release of a significant amount of heat in the interior of the planet, which may be enough to support noticeable geological activity. It turns out that the small radius of the orbits not only creates the problem of heat transfer from one side of the gravitationally captured planet to the other, but can itself partially solve it.
article by Peter Wheatley, published in 2016, immediately after the discovery of the first three planets, provides data on ultraviolet and X-rays TRAPPIST-1 stars. And it almost does not yield to the sun. Given that exoplanets are much closer to the star and, most likely, not protected by a strong magnetic field, the radiation and hard radiation on their surface should significantly exceed Earth's indicators.
In addition, such stars are much less stable than the Sun, and frequent flares and prominence ejections are also unlikely to contribute to an even and healthy tan for would-be Trappistarians (?). The same (and even more pessimistic) assessments are given in a just-published article by Jack O'Malley-James from Cornell University - only a very specific composition of the planet's atmosphere can save its surface from the damaging effects of X-rays. The presence of a large amount of ozone is especially important. As a consolation, we can say that class M8 stars live 500 times longer than the sun(up to a trillion years, which far exceeds the age of the Universe) and, since the star is still very young - it is only 500 million years old, the Trappisterians (?) have a lot of time left to adapt to an aggressive environment.
What's next?
However, all of this is just speculation. Astrophysicists from other scientific groups have already applied to use the Hubble telescope to attempt to "shine" the atmosphere of planets as they next pass through the disk of a star, and Kepler has been observing TRAPPIST-1 for some time, collecting new data on transits. Well, and, of course, the launch of the space IR telescope " James Webb"assigned to next year, is also eagerly awaited - its huge mirror, which is six times larger than that of the Hubble, should be enough to obtain new information about this amazing system.
Marat Musin
The editors are grateful to Vladislav Viktorovich Sidorenko, Professor of the Department of Theoretical Mechanics of the Moscow Institute of Physics and Technology, for his help in preparing the material.
Scientists in 2016 discovered seven Earth-sized planets near the star TRAPPIST-1 in the constellation Aquarius, three of which have conditions suitable for the existence of life. According to the researchers, this system is an "ideal laboratory" for studying alien worlds, and possibly the best place in the galaxy to search for life beyond Earth. Two planets have been discovered using ground telescope Trappist, and five more with the help of the Spitzer telescope located in space.
The surface of the planets is likely rocky, scientists write. Follow-up studies will allow researchers to establish whether there is water there. Scientists hope to study discovered planets using the James Webb telescope, which will be launched in 2018. The discovered planets are much closer to their star than the Earth is to the Sun. However, unlike the Sun, TRAPPIST-1, around which the planets revolve, is a cold red dwarf. Because of this, even on planets close to it, water can remain.
The planets are located very close to each other, so from each of them you can see the neighboring ones.
In May 2016, NASA confirmed the existence of 1,284 exoplanets - planets orbiting a star outside the solar system. The first evidence of the existence of such planets appeared in 1995.
In April 2014, NASA announced the discovery of the exoplanet Kepler-186f. She was named after orbiting telescope"Kepler", with which it was discovered. She is in planetary system the red dwarf Kepler-186 in the constellation Cygnus at a distance of 492 light-years from Earth. The planet revolves around the star at a distance favorable for the emergence of life, it is 10% more earth. In this regard, the researchers do not exclude that water in liquid form may exist on it.
The existence of a planet as similar to Earth as possible was announced again by NASA in July 2015. new planet also named after the telescope - Kepler 452b. The distance to the star around which it revolves is 1400 light years. The discovered planet is one and a half times the size of the Earth. This makes it a more "promising" analogue of ours than those that have been found orbiting cool stars, the scientists noted, Dozhd TV reported.
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NASA experts immediately discovered seven analogues of the planet Earth around the recently discovered star TRAPPIST-1 in the constellation of Aquarius. These celestial bodies similar in size and mass to the Earth. At the same time, three of the seven planets are located in the center of the "life zone" and, presumably, have water and a thick atmosphere.
O sensational discovery experts announced during a press conference, which was broadcast live on the official website of NASA. In addition, the breakthrough discovery of astronomers was written by the journal Nature.
"This discovery could be a significant step in the search for habitable environments and places that support life," NASA said, commenting on the discovery of planets in the TRAPPIST-1 star system, 40 light years away from Earth.
All discovered planets are similar in size to the Earth - their radius is from 0.7 to 1.08 of the radius of our planet, and their mass is from 0.41 to 1.38. Accordingly, their density is equal to that of the earth or slightly lower than it. This indicates their rocky nature or that they are oceanic planets.
Unlike Earth, the Seven Sisters orbit TRAPPIST-1 in a very tight orbit. On these planets, the year lasts from one and a half days to about two weeks.
Wherein last planet system, TRAPPIST-1h, is located about four times closer to the star than Mercury approaches the Sun.
As for the probability of the development of life, the three central planets - d, e and f - so far have the most claims for this role.
According to scholar Emory Trio of Astronomical Institute in Cambridge, greatest chance for the origin of life, planet f has a climate that is mild and cool enough for water and organic matter to exist on it.
In May 2016, astronomers from the American University of MIT announced the discovery of an unusual star system - TRAPPIST-1, only 40 light-years away from the Earth in the direction of the constellation Aquarius, recalls RIA Novosti.
Even then, scientists suggested that the three planets revolving around this red dwarf are inside the "zone of life", where water can exist in liquid form, and their mass, presumably, is comparable to that of the earth.
Later, scientists studied the spectrum of the rays of the star TRAPPIST-1, which passed through air envelopes planets on their way to Earth, and found that they were rocky planets similar to Earth. In addition, hints of the presence of water, oxygen and carbon dioxide in their atmospheres have been found.
However, until recently, not all astronomers agreed that these planets really exist. Critics have pointed out that the periodic dips in the brightness of the star, from which they were detected, could be generated by an invisible luminary to us - the TRAPPIST-1 satellite.
Michel Gillon, an astronomer at the University of Liege, meanwhile warned that the discovery of a family of seven planets does not yet allow us to talk about how often multiplanetary planets are found in our galaxy. star systems similar to or similar to the solar system.
"Here we are dealing with a relatively rare type stars, some of the coldest and quietest objects Milky Way. We do not expect that analogues of the solar system can arise in such stars - they simply do not have enough building materials to create major planets like Jupiter or Saturn. Therefore, we have not yet found analogues of the solar system in red dwarfs and are unlikely to find them," he explained.
At a press conference NASA scientists announced that in the constellation Aquarius, a system of 7 Earth-sized planets was discovered near a single star TRAPPIST-1, NTV reports.
On February 22, a NASA press conference was held, during which employees announced the discovery of seven planets in the constellation of Aquarius, three of which may be suitable for the existence of life. They are located at a distance of 40 light years from Earth.
The discovery took place back in 2016, but agency employees reported it only now. The planets are near the star TRAPPIST-1. Their size is the same as that of the Earth.
As NASA researchers noted, such a system is an ideal laboratory for studying alien worlds. Now scientists will find out if there is water on the discovered planets.
In addition to studying extraterrestrial finds, researchers will have to name celestial bodies. So far, the plans are to name them with letters of the Latin alphabet in accordance with their distance from the TRAPPIST-1 star. The process of naming exoplanets is a "pretty delicate" process, according to the planet-discovering team of Mikael Gillon. In this case, for example, it is easier with asteroids.
What does a new discovery mean for earthlings
Corresponding member Russian Academy cosmonautics named after Tsiolkovsky Andrey Ionin commented to REN TV reporters NASA discovery. He said that it was very interesting, but there could be no talk of making the way to new planets. And this is due to a lack of funding.
Why the discovery should be treated with some skepticism
Such achievements often appear in science: for example, at the beginning of the twentieth century, they discovered the most close star, or found the most big star in the universe - for its time it is important discoveries, — explained Metro Candidate of Physical and Mathematical Sciences, Senior Researcher Astrometry Laboratories and Stellar Astronomy Pulkovo observatory Maxim Khovrichev. - Here we are talking about such a case when 3 planets were in the "habitat zone". This is a very conditional concept, with these planets in terms of life (if we talk about life earth type) things are not going well. Because they are very close to the brown star. And this star is one that "breathes" - on the threshold between brown dwarfs (chemical stars) and stars. Smoldering object. But even these objects are not as calm as the Sun. The peculiarity of their structure is that there is very serious convection, mixing of matter - a large current, a large magnetic field, very strong flashes. Therefore, planets that are at such small distances are subject to " magnetic storms", which can drive very deeply all the rudiments of life.
Well, another difficulty is that, usually, when a massive body (giant star) is relatively small (the size of the Earth), then rotation synchronization occurs, and the planet always faces the star on one side. That is, on one side is eternal night, on the other - eternal day. The temperature difference is large, so if there is an atmosphere, the gas flows back and forth. With a very big stretch, you can find that something will live there. Rather, on Mars more favorable conditions for the development of life than there.
