The recently discovered TRAPPIST-1 star in the constellation Aquarius turned out to be the mistress of seven Earth analogs at once, and three of them are located in the center of the "zone of life" and presumably have water and a thick atmosphere, according to an article published in the journal Nature.
“Before the discovery of the TRAPPIST-1 system, we knew of only four real earth-like planets that we could study - Earth, Mars, Venus and Mercury. Now their number has increased by seven, and we can study them not in five to ten years, but right now. It can be expected that the first news about their properties will appear in the coming weeks and months. The history of TRAPPIST-1 is just beginning,”comments Michel Gillon, an astronomer at the University of Liege (Belgium).
Seven sisters
In May last year, astronomers from MIT announced the discovery of an extremely unusual star system - TRAPPIST-1, only 40 light-years distant from Earth towards the constellation Aquarius. Then it was reported that the three planets revolving around this red dwarf are located inside the so-called "zone of life", where water can exist in liquid form, and their mass is supposedly comparable to that of Earth.
Later, scientists studied the spectrum of rays of the star TRAPPIST-1, which passed through the air envelopes of the planets on the way to Earth, and found that they were rocky planets, similar to Earth, and also found hints of the presence of water, oxygen and carbon dioxide in their atmospheres. Nevertheless, not all astronomers were sure of the existence of these planets, noting that the periodic decreases in the brightness of the star, according to which they were detected, could be generated by the invisible satellite luminary TRAPPIST-1.
Gillon and his colleagues studied the properties of these planets by observing the star system with the TRAPPIST telescope in Chile and the Spitzer orbiting telescope. As the scientists note, they assumed that they could easily obtain information on the size, mass and composition of the atmosphere of the planets due to the small distance to TRAPPIST-1, the calm nature of the star and its small size, making it easier to observe the shadows of the planets on its surface.
These observations led to an unexpected discovery - it turned out that the planets are actually not three, but seven, and six of them are within the "zone of life." Thanks to the high resolution of telescopes and long-term observations, planetary scientists for the first time managed to very accurately measure both the diameter and mass of six of the seven planets and obtain some data on the composition of their atmosphere.
Promotional video:
TRAPPIST-1 planets compared to the solar system
Photo: NASA / JPL-Caltech
The riddle of the fifth planet
All 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 or slightly lower than that of the Earth, which indicates their rocky nature or that they are ocean planets.
Unlike our planet, the "seven sisters" revolve in a very close orbit around TRAPPIST-1 - a year lasts from one and a half days to about two weeks. Even the last planet of the system, TRAPPIST-1h, is located about four times closer to the star than Mercury approaches the Sun.
At the same time, almost all planets should be dominated by terrestrial or Mars-like weather with average surface temperatures around zero or 20-30 degrees below zero. Only the first two planets are out of this trend - their temperatures exceed 70-100 degrees Celsius, which probably makes them more like Venus than Earth.
If we talk about the likelihood of the development of life, then the three central planets - d, e and f - pretend to this role. According to Amaury Triaud of the Astronomical Institute in Cambridge (UK), planet f has the best chances for the birth of life, with a climate mild and cool enough for water and organics to exist.
The exact answer to this question can be obtained quite soon - according to Trio, some features of the climate of planet f and its neighbors will become known in the coming years, and the first reliable information on its habitability can be obtained within "the current decade."
Are we alone in the universe?
The possibility of the emergence of life on these planets, as Gillon admits, may be influenced by two unusual properties of the TRAPPIST-1 system. According to him, all the planets with a very high degree of probability are captured by the tidal forces of the star, as a result of which they always face one side of it. This can adversely affect the work of the planetary climate and make them virtually uninhabited.
In addition, the planets themselves are in the so-called orbital resonance. As a rule, this phenomenon arises as a result of the gravitational interaction of celestial bodies, which leads to the stabilization of their orbits and the emergence of a strict mathematical relationship between the periods of their rotation. For example, Saturn and Jupiter are synchronized in such a way that in two Saturnian years, Jupiter makes exactly five turns around the Sun.
Such processes, as the Belgian planetary scientist explains, can warm up the bowels of the planets of the TRAPPIST-1 system and cause powerful outbreaks of volcanism, similar to those that occur on Io, the satellite of Jupiter. This factor will also affect the favorableness of the planets for the origin of life, although it is difficult to say with certainty whether in a positive or negative direction.
This is how the artist imagined the planet TRAPPIST-1f, the closest candidate for the role of Earth's twin
Photo: NASA / JPL-Caltech
The discovery of a family of seven planets near TRAPPIST-1, as Gillon told RIA Novosti, does not yet allow us to talk about how often multiplanetary star systems similar to or similar to the solar system are found in our Galaxy.
“Here we are dealing with a relatively rare type of star, one of the coldest and quietest objects in the Milky Way. We do not expect that analogs of the solar system can arise in such stars - they simply do not have enough building materials for large planets like Jupiter or Saturn to appear in them. Therefore, we have not yet found analogues of the solar system in red dwarfs and are unlikely to find them,”the scientist explains.
If we talk about stars similar to the Sun, the data from Kepler and other telescopes, says Gillon, show that such systems are extremely rare. According to his estimates, only 10% of the planetary systems of such stars will be similar in their structure to the solar system. There are no statistics for an accurate estimate of this proportion yet, but the Belgian scientist is sure that the Solar System is a very rare and almost unique thing for the Galaxy. Systems like TRAPPIST-1 should be much more common there.
In any case, TRAPPIST-1 has initially high chances of the origin of life, since such stars live tens and hundreds of times longer than the Sun and other relatively large stars. As Gillon puts it, the Sun will go out long ago when TRAPPIST-1 has not yet emerged from childhood, which gives great chances for the birth of life in the future or even in the past.