Clingy Alien Planets May Fling Their Moons Out of Orbit
http://www.space.com/35460-clingy-alien-planets-may-lose-moons.html
Alien planets that orbit especially close to their stars have a bigger chance of losing their moons, which may reduce
the chances that habitable alien moons will survive for very long around those planets, a new study finds.
In the past 20 years or so, astronomers have confirmed the existence of more than 3,400 worlds outside Earth's solar system.
These discoveries have revealed that many exoplanets are very different from those seen in Earth's solar system; for instance,
about 40 percent of exoplanets discovered to date orbit their stars at least 10 times closer than Earth orbits the sun.
(In comparison, Mercury is at most about three times closer than Earth is to the sun.)
In Earth's solar system, there are far more moons than planets, with Jupiter alone having at least 67 moons. Previous work has
suggested that exomoons, or moons around exoplanets, could be as big or larger than Earth. If an exoplanet happens to lie in
a star's habitable zone — the area in which worlds have surface temperatures warm enough to host liquid water — then an Earth-
size exomoon around such a planet could potentially harbor life.