There Might Be Rain In The Augur For At Least One Faraway Planet

Far outside our solar system, it’s called K2 18b. Data from space telescopes and computer models suggest that this planet’s atmosphere hosts water vapor. If true, it could be the first exoplanet that has liquid water — an essential ingredient for life as we know it.
“Water vapor lives far and wide in the universe,” says Björn Benneke. He is an astronomer in Canada at the University of Montreal. On September 10, his team reported the potential discovery of water on K2 18b at arXiv.org. “It’s not so easy to make liquid water,” Benneke notes. One needs the right pressure and the right temperature, he has pointed out.
Astronomers first spotted K2 18b in 2015. They were using the Kepler exoplanet-hunting space telescope. Kepler revealed that the planet orbits a dim star known as a red dwarf. The star and planet are some 110 light-years from Earth. The planet is bit more than twice as wide as Earth, and has eight times Earth’s mass. So it’s “not an Earthlike planet,” Angelos Tsiaras explained in a September 10 news conference. He is an astronomer in England at University College London. His team also studies K2 18b. And they, too, have detected water vapor in K2 18's atmosphere. Tsiaras’ team reported that September 11 in Nature Astronomy. Though not Earthlike, the planet sits in what astronomers call a habitable zone. This is a region around a star where planets could have just the right temperatures to host liquid water. And liquid water appears important for life.
Could this planet host life?
In 2016 and 2017, Benneke’s group studied K2 18b using the Hubble Space Telescope. They wanted to see if the planet had an atmosphere. So they studied the planet as it passed in front of its star. The astronomers were looking to see if the planet’s atmosphere absorbs some of its star’s light. Astronomers can tell which molecules are in a planet’s atmosphere based on which wavelengths of starlight they absorb.
Tsiaras and his team accessed the data Benneke‘s had team collected from a public archive. Then it used specially designed computer software to analyze those data. This revealed the planet indeed had an atmosphere. And the wavelengths of light it absorbed were a signature for water vapor. That meant the planet’s atmosphere held water. That atmosphere also contains hydrogen and helium, the team reports.
Rain may fall — but how far?
Benneke’s group took the work a step further. They observed the planet with the Spitzer space telescope. By combining observations from Hubble, Spitzer and Kepler, they now believe the planet’s atmosphere has clouds. They appear to form at a specific spot. Knowing where this is, Benneke and his team simulated the planet’s climate. And that spot where the clouds form, they now say, could have the right pressure and temperature for liquid water to form and condense out as rain.
“It’s quite likely that this planet has liquid rain on it,” Benneke concludes.

By: Abhishek Singh
Content: https://www.sciencenewsforstudents.org/article/spotted-exoplanet-where-it-might-rain