Astronomers have discovered that an exoplanet–planets outside of our Solar System–hold the highest possibility to host human life because they found a clear indication of water and gases.
The researchers published their findings in the journal Nature Astronomy on Wednesday and identified the exoplanet as K2-18b, which is 110 light-years away from Earth in the Leo constellation.
“This is the first potentially habitable planet where the temperature is right and where we now know there is water,” said Angelos Tsiaras, an astronomer at University College London. “It’s the best candidate for habitability right now.”
However, Tsiarias noted that K2-18b is not an exact replica of Earth but rather has the potential to host life.
“Finding water in a potentially habitable world other than Earth is incredibly exciting,” said Tsiaras. “K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition. However, it brings us closer to answering the fundamental question: Is the Earth unique?”
Researchers first discovered K2-18b in 2015 by NASA’s Kepler spacecraft. It is eight times the mass of Earth and known as a super-Earth, or planets between the mass of Earth and Neptune.
It orbits a red dwarf star and completes one orbit around its star every 33 days. It is also much closer to its star than Earth is to the sun; from a mere 14m miles out, a sixth of the distance from the Earth to the Sun. Notably, however, the red dwarf is estimated to be much cooler compared to our Star.
Based on the researchers’ calculations, they believe the planet is at a similar temperature to that of Earth. Red dwarfs produce far less heat than the sun, but K2-18b is warmed to about 10C (50F). But the range extends to include temperatures much colder or warmer than Earth because of the constraints of their data.
The most interesting part of their discovery, however, is that they have clear indications that water exists on the planet.
In data collected by the Hubble Space Telescope between 2016 and 2017, they analyzed measurements of starlight from the red dwarf as the planet wandered across its face on eight separate occasions.
The data revealed that as K2-18b crossed in front of its star, wavelengths of light that are absorbed by water suddenly dropped off, and then rose again as the planet moved on.
The researchers said that this is a clear signature for water vapor in the atmosphere when they put the data through algorithms.
The detection of water vapor in the atmosphere of this exoplanet is particularly “exciting” to the researchers because the exoplanet also orbits around the sun in a habitable zone called the Goldilocks Zone. This particular area around a Star is considered likely to host life because it harbors the right amount of heat and energy for water to remain liquid on the surface.
They also observed the signatures of hydrogen and helium in the atmosphere, two of the most abundant elements in the universe.
“With so many new super-Earths expected to be found over the next couple of decades, it is likely that this is the first discovery of many potentially habitable planets,” said Ingo Waldmann, study co-author and lecturer in extrasolar planets at the University College London’s Centre for Space Exochemistry Data.
“This is not only because super-Earths like K2-18b are the most common planets in our Galaxy, but also because of red dwarfs – stars smaller than our Sun – are the most common stars.”
Today’s technology is too feeble to take photos of the surfaces of such distant worlds, and they are too far away to send probes to. The researchers believe that other elements like nitrogen and methane could also be present in the atmosphere, but only future observations by more advanced telescopes will reveal them.
The red dwarf star, which K2-18b orbits around is also suspected to be an active one, which is likely exposing the exoplanet to more radiation than Earth receives. This could render the planet uninhabitable as it may no longer be able to retain a life-sustaining atmosphere.
Similar to a study published in August, astronomers also discovered three potential planets capable of hosting life but continues to lack more sensitive instruments to say for certain.
In the future, astronomers may be able to get a clearer view and more significant data as NASA will soon be able to launch the James-Webb Space Telescope, which is touted to be the most advanced space-probing tool.