Hycean planets (ocean worlds with H-rich atmospheres) are thought to be promising spots for life, particularly around M-dwarfs, with the habitable zone being much wider than it is for terrestrial planets. But there’s a twist…
In a new paper accepted to ApJ Letters and on arXiv now, UW-Madison graduate student Joseph Livesey shows that tidal heating from even modest orbital eccentricity can heat close-in planets around M-dwarfs, shrinking the habitable zone significantly. To the right, you will find a summary plot from the paper showing the effect – the transparent region was the location of the known habitable zone, the opaque region is the updated limits including tidal heating. For low mass stars, tides can make a difference. What does that mean? If a Hycean planet has a giant outer companion, tidal forces can perturb it out of the habitable zone, even if the incident stellar flux looks fine.