Moons of rogue planets may stay habitable for billions of years
Scientists from the Excellence Cluster ORIGINS at Ludwig Maximilian University of Munich (LMU) and the Max Planck Institute for Extraterrestrial Physics (MPE) have found that moons orbiting free-floating rogue planets could maintain liquid water oceans for up to 4.3 billion years. The researchers say dense hydrogen atmospheres combined with tidal heating could keep these exomoons warm enough for life to develop, even without sunlight. Rogue planets are giant worlds ejected from their star systems during chaotic planetary formation, and previous work showed they may retain some of their moons. After ejection, the moons often end up in highly elongated orbits, and the gravitational stretching and squeezing generates internal heat through tidal heating. The team investigated hydrogen-rich atmospheres because hydrogen, under high pressure, can trap thermal radiation through collision-induced absorption, remaining stable at very low temperatures. The study also suggests tidal forces could create wet-dry cycles that may help produce complex molecules essential for life. Astronomers estimate there could be as many free-floating planets in the Milky Way as stars, greatly expanding the number of possible life-hosting worlds.
What’s reported
The study was conducted by scientists from LMU’s Excellence Cluster ORIGINS and the Max Planck Institute for Extraterrestrial Physics.
Moons around rogue planets could maintain liquid water oceans for up to 4.3 billion years.
Tidal heating from elongated orbits generates internal heat strong enough to keep oceans from freezing.
Hydrogen atmospheres, under high pressure, trap thermal radiation through collision-induced absorption, providing long-term insulation.
Carbon dioxide atmospheres, previously studied, would condense in deep space and lose warming ability after about 1.6 billion years.
Tidal forces may create wet-dry cycles that could help form complex life-building molecules.
Astronomers believe free-floating planets may be as common as stars in the Milky Way.
Key figures
David Dahlbüdding – doctoral researcher at LMU and lead author of the study
Dr. Giulia Roccetti – LMU physicist, involved in previous moon-retention research
Professor Dieter Braun – collaborated on the study
Sources: ScienceDaily
