I have heard that there are at least three Basic requirement for life exist in the universe, they are:

  • Source of Energy
  • Complex chemistry (including solvent/medium for chemical reaction)
  • Protection for external threat (e.g. high energy electromagnetic wave, asteroid etc.)

In earth, our major source of energy come from our sun, which provide enough heat to initial chemical reaction in our ocean.

One day, when I was searching the internet, I came upon the ideas of rogue planet, brown dwarf, tidal heating. Which keep me thinking of the possibility of life on the moon of a rogue planet (probability a large gas giant/ brown dwarf).

I have a naive thought on the situation , where the rogue planet radiation and its mass (effect of tidal heating), provide sufficient energy of the moon (hot enough to maintain solvent say water/methane) . And somehow the moon like Titan, which have a dense atmosphere, to protect the surface of the moon.

As I digging deeper, I find some other sources saying that, these kind of situation is not possible because of tidal locking (somehow related to small radius of orbit to keep the moon warm? not quite remember) or the moon atmosphere will be evaporated by the large rogue planet.

So, my question is would the moon of a rogue planet ever have chance like my naive situation exist?(What would be the ideal size of both planet and moon, and their orbital radius?) Or the situation is simply impossible, if so would there be other cases, where the moon of a rogue planet can support life to exist. (may be life within thick ice sheet? or not in the moon but in the planet?)

  • $\begingroup$ Related: astronomy.stackexchange.com/questions/28314/… BTW There are currently 48 questions on rogue planets here, did you check the other 47? Two of those (about life specifically) got closed as primarily opinion based. $\endgroup$
    – user1569
    Dec 4, 2019 at 6:58
  • $\begingroup$ Thank you for notification, but I find out those questions are focusing on the rogue planet itself. In this question my focus is on the moon surrounding the rogue planet for a specified configuration and assumption. $\endgroup$
    – C.Calvert
    Dec 4, 2019 at 7:11
  • $\begingroup$ Also, life in this question is not limit to complex life form. $\endgroup$
    – C.Calvert
    Dec 4, 2019 at 7:14

1 Answer 1


No one knows for sure, but the idea is plausible. There would not be enough radiation from a rogue planet to provide much help, but we know from the moons of Jupiter and Saturn that tidal heating can keep water liquid. There might have to be multiple moons for it to work. The outer moon keeps making sure the inner moon has an elliptical orbit, and as the inner moon gets farther and closer to the main planet, the tidal forces get weaker and stronger, causing a "squeezing and unsqueezing" that warms the moon.

Of course, at the distance of Jupiter the Sun still provides some warmth, so it would take a lot of tidal heating. But I don't think it's out of the question.


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