With data from the NASA/ESA Hubble Space Telescope, water vapour has been detected in the atmosphere of a super-Earth within the habitable zone by University College London (UCL) researchers in a world first.
K2-18b, which was discovered in 2015, lies 110 light years away from us in the constellation of Leo. This is a landmark discovery, because the alien world is potentially habitable, apparently orbiting its star at the right distance for liquid water to exist on the planetary surface.
It's twice the size of Earth with eight times the mass, and its star is unlike our sun. While the atmosphere contains water vapor, there's evidence suggesting it's quite thick, and that the planet may not have a surface in the first place. The planet, K2-18b (aka EPIC 201912552 b) orbits its red-dwarf star every 33 days. We assume that any planet capable of supporting life has to exist within the habitable zone (also sometimes called the "Goldilocks zone") of its host star. It bathes K2-18 b in a glow of ultraviolet light making the planet's surface not wholly conducive to human occupation. So, in their paper, they took the conservative approach and gave a broad-range estimate for the abundance of water - somewhere between 0.01 percent and 50 percent. Some super-Earths have turned out to be more like sub-Neptunes, with big gaseous envelopes, but this planet's average density is similar to the density of the Moon or Mars.
A group of astronomers may have found Earth's long-lost cousin, discovering the first ever "habitable" terrestrial planet with water in its atmosphere, according to new research aided by the Hubble telescope.
Scientists in the United Kingdom have made a "world first" discovery on a distant planet that hosts both water and temperatures which could support life.
Although the planet sits in the habitable zone of its solar system, scientists say that there is now no way to determine whether there are signs of life.
They then modelled the atmosphere using three different approaches: cloudless, with water vapour in a hydrogen-helium atmosphere; cloudless, with water vapour, hydrogen-helium and molecular nitrogen; and cloudy, with water vapour and hydrogen-helium. It is also necessary that the planet has an atmosphere to protect the planet from any harmful radiation coming from its host star. Additionally, it could have a hydrogen-rich atmosphere with just water all over. Like Earth, it has a temperate climate, a rocky core, and water.
"We have no analogue for those kinds of planets in our solar system", he said.
"The water vapor detection was quite clear to us relatively early on", lead author Björn Benneke, a professor at the Institute for Research on Exoplanets at the Université de Montréal, told Space.com in an interview.
So instead, our best bet is to do follow-up observations with two successors to Hubble: the James Webb Space Telescope, which is due to launch into orbit in 2021 but has been repeatedly delayed, and the European Space Agency's ARIEL space telescope, scheduled to launch in 2029.
These telescopes will also, hopefully, detect smaller planets more like our own.