Current Affairs

Hycean Worlds: Exoplanets

  • Posted By
  • Categories
  • Published
    7th Sep, 2021


Recently, some astronomers have identified a new class of exoplanets – Hycean worlds.

What is hycean planets?

  • The word Hycean comes from the words hydrogen and ocean.
  • These planets get formed due to the presence of substantial hydrogen in the atmosphere and large oceans (hydrogen and ocean = Hycean) on their surfaces.

Key- Points about the hycean planet

  • Hycean planets can be up to 2.6 times larger than Earth.
  • Hycean planets  have atmospheric temperatures up to nearly 200 degrees Celsius, depending on their host stars. 
  • This places them somewhere between Earth and giant planets like Neptune or Uranus.
    • Hycean planets “straddle the boundary between super-Earths and mini-Neptunes.
  • These planets may well be tidally locked meaning that
    • One side is always in daylight from the star it orbits.
    • The other side is perpetually in the dark, like our moon.
  • Tidal locking is the name given to the situation when an object’s orbital period matches its rotational period.

Characteristics of Hycean planets

  • Size alone is not enough to confirm whether a planet is Hycean. Numerous other features including 

    • The planet’s mass and temperature
    • The nature of the host sun and atmospheric properties are required for any potential confirmation.
  • These oceanic planets, called Hycean worlds, are covered by thick hydrogen-rich atmospheres.
  • Hycean planets include massive oceans, unfathomably hot temperatures (440° F), and atmospheric pressures up to a thousand times stronger than Earth's. 
  • The laws of thermodynamics claim that, in order for Hycean worlds to support life, average temperatures should not exceed roughly 250° F.
  • Hycean worlds seem so promising that the authors decided to create two sub-categories:
    • Cold Hycean  worlds are located at the outer edges of their habitable zones and receive such little light that they grow cool (but not too cool).
    • Dark Hycean  worlds are found slightly beyond the inner edges where the side of the planet facing away from the sun could be "habitable even if the dayside is too hot.