“Is life a rare thing in the universe?”, is a question many scientists ask. We know many conditions that should be fulfilled to create life. Searching for planets that fir our description is a very intensive study, there are many people working on the matter in many ways. Therefore, lots of possibly life-supporting planets had been found, though let’s take a look on the most promising ones.
1. Ross 128b
First of all, the closest one, discovered in 2017. “Although Ross 128b is not Earth's twin, and there is still much we don’t know about its potential geologic activity, we were able to strengthen the argument that it's a temperate planet that could potentially have liquid water on its surface," lead author Diogo Souto, of the Observatório Nacional in Rio de Janeiro. Ross 128b circles a red dwarf only 11 light years away. It is probably rocky planet, about 1.3 times Earth’s mass. After analysing Ross 128- our planet mother star- and by using information about star’s temperature (about 3000 degrees), along with data about location of Ross 128b's, they came into the conclusion, that temperature on the planet’s surface is about 21 Celsius degrees. We do not know anything about air or atmosphere on the planet, though other collected data seems promising.
2. Gliese 667 Cc
The next one is orbiting a red dwarf star, that is a part of trinary system. Its mass is probably 4 times bigger than Earth’s and receives about 90% of sunlight Earth receives. The equilibrium temperature, that considers an object as a black body heated by a star, doesn’t involve atmosphere or any other effects, is 4.3 degrees Celsius (for Earth is -18.5). Recent researches confirmed, that planet’s atmosphere is quite similar to Earth’s and temperature on the surface is around 30 degrees Celsius.
3. TRAPPIST-1 system
Another interesting example is the solar system of ultracold dwarf, where scientist found four possibly life-supporting planets. There are located 39 light years from Earth, each one is quite different, though they are all in habitable zone. TRAPPIST-1d is the smallest one (30% Earth’s mass), with almost 5% of its mass, that can be water or ice layers. The next one is TRAPPIST-1e, that is almost Earth-sized, has the same gravity, temperature and it also has a compact atmosphere. In the end of 2018, researches from University of Washington claimed that from the TRAPPIST-1 system, TRAPPIST-1e is most life-supporting. Then there are TRAPPIST-1f and TRAPPIST-1g. Both are almost Earth-sized, the first one has a massive steam-water envelope, the second one may also contain water.
4. Proxima Centauri b
Let’s talk a little about the closest exoplanet, only 4 light years away. Proxima Centauri b orbits Proxima Centauri, a part of triple star system Alpha Centauri. Proxima Centauri is a red dwarf star whose mass is only 12% of Sun’s mass, it is also a lot colder than our star. When it comes to the planet, it receives 70% of energy Earth receives, has similar size, though its habitability depends on many other condition. Scientists try a lot of possible models of Proxima Centauri b’s history, that affects if planet has liquid water and atmosphere today. In the end of 2017, NASA came with an idea of launching an interstellar probe by 2069. Its mission would be searching for any bio-signatures and researching the whole system.
5. Kepler 186F
Last but not least, the most distant one, 582 years away from Earth. Planet’s size is not exactly known, however its radius is probably 11% bigger than Earth’s and it’s mass about 1.4 times that of Earth. Study performed in June 2018 by Yutong Shan and Gongjie Li suggested, that Kepler 186F may have stable climate and seasons. Kepler 186F is one of the first exoplanets located in habitable zone ever discovered. It has been a target of SETI mission and over the years it’s been one of the public’s favourites.
As we can see, there are many exoplanets that can support life, but nobody found any extraterrestrial life. Arthur C. Clarke said “Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.” , though most scientists believe that somewhere out there, in the depths of cosmic ocean, there are many forms of life. We are trying to find it, and it may be on one of the mentioned planets, albeit no matter where and what is it, it will change our look on the universe forever.