K2-18b

• K2-18b is now the only planet orbiting a star outside the Solar System known to have both water and temperatures that could be potentially habitable.

K2-18b

• About 110 light years from Earth, an exoplanet eight times the mass of Earth orbits a star. Called K2-18b, it was discovered in 2015 by NASA’s Kepler spacecraft.
• The researchers used 2016-17 data from the Hubble Space Telescope and developed 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.
• It resides in a habitable zone — the region around a star in which liquid water could potentially pool on the surface of a rocky planet.
• Scientists have found signatures of water vapour in the atmosphere of K2-18b. The discovery of water vapour is not the final word on the possibility of life.
• That makes it the only planet orbiting a star outside the Solar System that is known to have both water and temperatures that could support life.

Not ‘Earth 2.0’

• K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition.
• For one thing, K2-18b’s size and surface gravity are much larger than Earth’s. Its radiation environment may be hostile.