A team of scientists from the University of Cambridge (England) has determined, after analyzing the mass, radius and atmospheric data of exoplanet K2-18b , that it is possible that this world houses liquid water in habitable conditions under its hydrogen-rich atmosphere .
This planet, averaging between Earth and Neptune, is only 124 light years distant from Earth and … could be teeming with life . This discovery, published in The Astrophysical Journal Letters, broadens the range of planets that astronomers can include in their search for extraterrestrial life.
K2-18b is orbiting a red dwarf star K2-18, right in the middle of the habitable zone, not so hot that liquid water ends up evaporating from the surface, and not so cold that it freezes completely.
Does the name sound familiar to you?
It was discovered in 2017, but it will sound like a few months ago, as the planet made headlines last year when astronomers found water vapor in its atmosphere. This was an exciting find, as it was the first potentially habitable planet on which water vapor had been found in its atmosphere. However, its potential habitability was not so clear at the time. Also, we have the clearest example on Mars. Not just being at the correct distance from the star is important in proclaiming the habitability of a planet.
It is relatively similar to Earth: it has a radius 2.6 times larger and a mass 8.6 times that of Earth. Of course, we still do not know what its surface is like. Researchers can’t say for sure whether it has a rocky exterior and a thin atmosphere, like Earth, or a dense hydrogen atmosphere over a high-pressure ammonia-water ocean and a metallic core, like Neptune, conditions that are nothing. suitable for life.
How is the planet?
With the new data they concluded that the heart of K2-18b can be … anything from an almost pure iron ball with a not too thick hydrogen atmosphere, to something more like Neptune, to a water world with an atmosphere lighter and Earth-like ocean conditions.
The researchers found that the maximum extent of the hydrogen envelope allowed by recent data is around 6% of the planet’s mass. The minimum amount of hydrogen is about one millionth by mass, similar to the mass fraction of Earth’s atmosphere. The most suitable scenario seems to be an oceanic world, with liquid water below the atmosphere and temperatures similar to those found in Earth’s oceans.
¿Habitable?
It is not conclusive proof that K2-18b is habitable, but it does show that on exoplanets like this it is something that could happen. Therefore, we must not limit our search for habitable worlds to rocky planets of habitable zones. It is time to be more open-minded.
“Future observations, for example with the James Webb Space Telescope, will have the potential to refine our findings,” the authors wrote. “We argue that planets like K2-18b may have the potential to approach habitable conditions and searches for biosignatures should not necessarily be limited to smaller rocky planets.”
Referencia: Nikku Madhusudhan et al. The interior and atmosphere of the habitable-zone exoplanet K2-18b. The Astrophysical Journal Letters, 2020 DOI: 10.3847/2041-8213/ab7229
