Hycean Worlds: Exoplanets:
Some astronomers have identified a new class of exoplanets – Hycean worlds.
- The word Hycean comes from the words hydrogen and ocean. Planet-wide oceans and hydrogen-rich atmospheres might cover these worlds.
- They are also uniquely alien, up to 2.6 times the diameter of Earth, with temperatures up to 200 degrees celsius and thick hydrogen atmospheres.
- This places them somewhere between Earth and giant planets like Neptune or Uranus.
- With no analogs in the Solar System, these planets are variedly classed as super-Earths or mini-Neptunes depending on inferences about their bulk compositions based on their densities.
- These planets, unlike most mini-Neptunes, may have solid surfaces, like Earth. Many of the known Hycean candidates are larger and hotter than Earth, but still would be able to host large oceans.
- Some Hyceans orbit so close to their stars that they’re tidally locked, with one hot dayside and one eternally dark nightside. And some orbit very far away, receiving very little stellar radiation. But life could exist even on such extreme Hyceans.
- Tidal locking is the name given to the situation when an object’s orbital period matches its rotational period.