On a large exoplanet found conditions suitable for the origin of life

UNITED STATES (OBSERVATORY NEWS) — Not so long ago, the world spread around the news: on a planet lying in the habitable zone of its star, water was first discovered. Now astronomers are convinced that the temperature and pressure under the atmosphere of this world can indeed be favorable for living organisms.

The achievement is described in a scientific article accepted for publication in the Astrophysical Journal Letters. In the meantime, you can familiarize yourself with her preprint .

Recall that the exoplanet K2-18b became the first world in the habitable zone in the atmosphere of which water was detected . We explain that the habitable zone is the area around the star in which the existence of liquid water on the surface of the planet is possible.

However, this only means that there cannot be known to be liquid water outside this zone, and not that it certainly exists within its borders.

The specific conditions on the surface of a particular exoplanet depend not only on the distance to the local sun; the composition and thickness of the atmosphere of each particular world play a key role.

And with this, K2-18b is not easy. By mass, it exceeds the Earth by 8.6 times. Therefore, some researchers call it super-Earth, while others call it sub-Neptune (the mass of Neptune, we recall, exceeds the earth by 17 times).

According to experts, such worlds should have a thick atmosphere of hydrogen and helium. The problem is that if it is too thick, then the pressure and temperature on the surface will be extreme even for the most hardy organisms .

Therefore, scientists from the University of Cambridge decided to find out what the conditions under the K2-18b gas shell can be. To do this, they used observational data on the mass, radius and atmosphere of the planet.

Researchers confirmed the existence of water vapor on this exoplanet, and also noted an unexpectedly low methane and ammonia content. Then they calculated the possible thickness of the gas shell.

It turned out that the mass of the atmosphere is at most 6% of the mass of the entire planet, but, most likely, its contribution is much less. The lower boundary is about a millionth of the mass of a celestial body (as on Earth).

Moreover, a number of possible options allows the existence of oceans on K2-18b at temperatures and pressures similar to Earth’s.

Of course, there are less optimistic scenarios. To find out what is really going on under the gas veil of a huge planet, only further observations will help. In particular, astronomers have high hopes for the James Webb infrared telescope, whose launch is scheduled for 2021.

Note that planets with a mass larger than the earth, but smaller than Neptune, make up the majority of the worlds known to astronomers (and there are more than four thousand of them). Yes, and stars similar to K2-18 (red dwarfs) in the Galaxy more than 70%. So K2-18b is a kind of typical case, and its study is very important for understanding how many potentially inhabited worlds can be in the Milky Way.


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