K2-18b — a potentially ‘habitable’ planet

  • Category
    Science & Technology
  • Published
    19th Sep, 2019


Water vapour discovered on potentially ‘habitable’ planet. Using Hubble Space Telescope, scientists also detected the presence of hydrogen and helium in K2-18b's atmosphere.


  • K2-18b an exoplanet that orbits around a small red dwarf star K2-18, nearly 110 light-years away in the constellation Leo.
  • K2-18b was first discovered in 2015 by Nasa's now retired Kepler space telescope.
  • It was found orbiting within the red dwarf star's habitable zone, making it an ideal candidate to have liquid surface water.
  • Having a mass that is eight times greater than Earth's, K2-18b is also known as Super-Earth exoplanets with masses between those of Earth and Neptune.
  • The Kepler satellite mission discovered nearly two-third of all known exoplanets. While the mission indicated that five to 20 per cent of these are located in the habitable zone of their stars.
  • Water vapour has been detected on K2-18b a potentially ‘habitable’ planet by Nasa and the European space agency's Hubble Space Telescope.
  • K2-18b could be the only exoplanet known to have both water and temperatures in its atmosphere to sustain liquid water on a rocky surface
  • The new finding offers an 'unprecedented opportunity' to gain insight into the composition and climate of habitable-zone planets.
  • K2-18b is not ‘Earth 2.0’ as it is significantly heavier and has a different atmospheric composition.
  • This study contributes to our understanding of habitable worlds beyond our Solar System and marks a new era in exoplanet research.

What Is an Exoplanet?

  • All of the planets in our solar system orbit around the Sun. Planets that orbit around other stars are called exoplanets.
  • Exoplanets are very hard to see directly with telescopes. They are hidden by the bright glare of the stars they orbit.
  • There are many methods of detecting exoplanets. Transit photometry and Doppler spectroscopy have found the most, but these methods suffer from a clear observational bias favoring the detection of planets near the star; thus, 85% of the exoplanets detected are inside the tidal locking zone.
  • One way to search for exoplanets is to look for "wobbly" stars. A star that has planets doesn’t orbit perfectly around its center. From far away, this off-center orbit makes the star look like its wobbling.
  • The most massive planet listed on the NASA Exoplanet Archive is HR 2562 b, about 30 times the mass of Jupiter.

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