Why in News?

• Astronomers have for the first-time discovered water in the atmosphere of an exoplanet with Earth-like temperatures that could support life.

Highlights:

• K2-18b is the only planet orbiting a star outside the Solar System known to have both water and temperatures that could be potentially habitable.
• It is known to have both water and temperatures that could be potentially habitable.
• The discovery is the first successful atmospheric detection for an exoplanet orbiting in its star’s ‘habitable zone’, at a distance where water can exist in liquid form, they said.
• The team used archive data from 2016 and 2017 captured by the ESA/NASA Hubble Space Telescope and developed open-source algorithms to analyse the starlight filtered through K2-18b’s atmosphere.
• The results revealed the molecular signature of water vapour, also indicating the presence of hydrogen and helium in the planet’s atmosphere.
• K2-18b’s size and surface gravity are much larger than Earth’s. Its radiation environment, too, maybe hostile.
• They believe that other molecules including nitrogen and methane may be present but, with current observations, they remain undetectable.

K2-18b:

• K2-18b was discovered in 2015 and is one of hundreds of super-Earths — planets with a mass between Earth and Neptune — found by NASA’s Kepler spacecraft.
• Exoplanet K2-18b is eight times the mass of Earth.
• The planet orbits the cool dwarf star K2-18, which is about 110 light years from Earth in the Leo constellation.
• However, the researchers said, “K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition.
• They also said that further studies are required to estimate cloud coverage and the percentage of atmospheric water present.