Friday, July 3, 2015

'Exomoons' Capable of Supporting Life May Be Common

Mars-Mass Exomoons Around Alien Planet

Exomoons are the wild card in the ongoing chase for habitable worlds.

Astronomers have discovered more than 1,900 exoplanets, a few of which might be friendly to life, but no moons circling these alien bodies have turned up as of yet. Astronomers do not know how common exomoons might be or, for that matter, what they might be like.

A new study fills in an important gap in the developing theoretical framework regarding exomoons. The paper looks at a special set of exomoons located in the habitable, or "Goldilocks zone" — the not-too-cold, not-too-hot band where water neither freezes nor boils off a planet’s (or moon’s) surface. [How Habitable Zones for Alien Planets and Stars Work (Infographic)]

The research hearkens back to the holy grail of exoplanet hunts: an Earth-like clone. Astronomers have fervently sought a world the mass and size of our own, orbiting at a similar distance from a star similar to our sun.

To date, however, most worlds with known masses, and orbiting at Earth-like distances from sun-like stars, are "super-Jupiters." As their name implies, these behemoths are even-more-jumbo versions of Jupiter, our solar system’s biggest planet. Such bloated, gaseous worlds, of course, would not themselves be habitable in any way.

But if these super-Jupiters orbiting in habitable zones could form large exomoons, these bodies might be excellent candidates for supporting life. So far, most exomoon formation models have been restricted to exoplanets with masses in the Saturn-Jupiter range, because scenarios similar to our solar system have primarily piqued astronomers. Given the fact that dozens of super-Jupiters are now known to occupy Earth-like real estate around sun-like stars, the study authors figured it was high time to broaden those models.

"We wanted to extend, for the first time, the calculations for the formation of water-rich moons around gas giants beyond the Jupiter mass regime," said lead author René Heller, a postdoctoral fellow in astrophysics at McMaster University in Ontario, Canada.

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