New computer simulations suggest that Uranus and Neptune, two ice giants, are able to form their own moons – just like Saturn and Jupiter. The number of moons, some potentially habitable, could therefore be much larger than expected in the universe.
The solar system is home to many moons. Among them, only two are, as of now at least, of interest in the question of extraterrestrial life: Europa, the icy moon of Jupiter, and Enceladus, the icy moon of Saturn, both formed in the disk of their rather large host planet. It was thought, however, that planets like Uranus and Neptune, giant icy planets much smaller than Jupiter and Saturn, could not form their own moons. However, recent simulations suggest that they are quite capable on the contrary.
The five main moons of Uranus and the only large moon of Neptune (Triton) have a different story despite the fact that these two planets are very similar. Though scientists believe that Triton was captured by Neptune, they have always thought that the moons of Uranus could have formed like the moon of the Earth, following a cosmic collision. “It was believed that Uranus and Neptune are too light to form such a disk,” notes Judit Szulágyi, lead author of the study. Whether it is the result of a collision for Uranus or a capture for Neptune, these two means of forming moons remain rare in the Universe.
But recent computer simulations seem to prove the idea that Uranus and Neptune were indeed able to form their moons from gas dust discs during their formation. An icy moon would be able to form in 105 years, say the researchers. Thus, for its part, Uranus was able to form its five moons without the help of anyone. This was probably also the case for Neptune, but these moons were then ejected by the arrival of Triton.
We know that giant planets like Jupiter and Saturn are capable of producing moons formed in gaseous discs during the last phase of their formation. But this new study suggests that smaller planets, like ice giants that seem to abound in the Universe, can also form such disks, and thus moons.
“If ice giants can also form their own satellites, it means that the moon population of the Universe is much more abundant than previously thought,” says the astrophysicist. We can therefore expect many more discoveries of exomoons over the next decade. ” With a more important population of frozen moons in the Universe, we can also expect more potentially habitable worlds.