The two exoplanets of the TRAPPIST-1 system, most likely, have water in liquid form, which means that life is also possible. This is stated in a new study by scientists from the US Planetary Institute. However, experts consider the American conclusions premature, pointing out that these planets probably lack the atmosphere necessary for life.
"Relatives" of the Earth
The TRAPPIST-1 system has been perhaps the main space newsmaker since its opening in 2016. The ultracold dwarf is located in the constellation Aquarius, 39 light-years from Earth. TRAPPIST-1 is slightly larger than Jupiter but about 90 times heavier.
At first, as many as seven planets were discovered around the star. Then it turned out that they were all earthlike.
An international team of scientists led by astrophysicists from the US Planetary Institute suggested that the planets are composed of ice, rocky rocks and iron, and determined their structure using computer simulations. As a result, experts obtained new, updated values of the masses for each of the planets, and also estimated the amount of water contained on them.
“Since the star TRAPPIST-1 is old and dim, it is relatively cool on the surfaces of its planets: from 127 ° C to -107 ° C. The planets are also very close to their star and make a complete revolution around it in just a few days: from 1.5 to 12. Since the orbits of these planets are slightly elliptical, and not circular, then, rotating around the star, they are then closer to it then further away from it. Under the influence of the gravitational attraction of the star on the planets, the amplitudes of the tides change. This process is called tidal heating. All this contributes to the fact that heat is generated in their depths, which supports geological activity in the planets,”says one of the study's authors, Amy Barr.
Planets of the TRAPPIST-1 system. NASA / JPL-Caltech.
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The report also reports on the heat transfer processes in the mantle of each planet. The results showed that the second and third (if you count from the star) planets probably had partially molten rock mantles. Moreover, there are traces of siliceous magma on one of the surfaces, probably due to the eruption caused by tidal heating. Such volcanic activity is characteristic of Jupiter's moon Io.
The planets of the TRAPPIST-1 system have another interesting feature: when they approach directly to the star, they are deformed under the influence of its gravitational field, becoming like an egg. When removed, the planets take on a spherical shape again.
"Quite moderate" conditions
Even last year, scientists talked about three planets of the TRAPPIST-1 system, which are located in the so-called habitable zone: where it is not too hot or cold for water to be in a liquid state. And this, in turn, would create conditions for the origin and development of life.
As a result, two planets most suitable for life were identified. They are named TRAPPIST-1d and TRAPPIST-1e. At the first, the average temperature is +15 ° C. The second is cooler: the climate is about the same as in Antarctica. But this astrophysicists called "quite moderate" conditions. Scientists believe that planet d may even be covered by an entire ocean.
Hastened to conclusions
However, some scientists doubt that the study of Americans provides sufficiently convincing and weighty scientific arguments for such conclusions.
“The research is purely theoretical. Its authors did not mention the radiation, the level of which on these planets is clearly higher than that of the Earth. The TRAPPIST-1 star is very active. There is still a lot to study before declaring whether these planets are suitable for life - for example, to study in detail the composition and density of their atmosphere in order to understand how much it can protect exoplanets from energy emissions, the astronomer, academician said in an interview with RT. Yuri Balega, bureau member of the Physical Sciences Division
According to the expert, in 2019 NASA will launch the new James Webb telescope, which will allow to study this system in more detail, test it for the presence of water and potential suitability for life.
The James Webb Space Telescope. NASA / Chris Gunn.
Skeptics doubt that TRAPPIST planets - including those declared potentially habitable - have a suitable atmosphere. Opponents of the "habitability" of exoplanets say that the radiation of "native" stars often destroys the atmosphere of their satellites.
“More than 3.5 thousand exoplanets have already been discovered, and more will be discovered. Some of them are already in the habitable zone, there is liquid water, a suitable temperature. We can say that the conditions for organic life are favorable. But many of these planets, including the TRAPPIST-1 system, revolve around low-luminosity red dwarfs. They are very characterized by high chromospheric activity, when very strong flares occur, many times stronger than on the Sun. Therefore, there may be many planets around red dwarfs, but due to the activity of their stars, they are, of course, not suitable for life - at least the way we imagine it on Earth, explained RT Doctor of Physical and Mathematical Sciences, scientific director of the Institute Astronomy RAS Boris Shustov.
Anastasia Ksenofontova