Friday, May 29, 2009
One unresolved issue for quite some time had been whether other stars could have planets, since until the 1990s the only example of a star with a planetary system had been our own, and without a larger sample size it would be impossible to know for sure whether other stars really had planets, or whether the majority of them were bereft of them and simply existed by themselves.
Fast-forward to 2009 and we know of over 300 extrasolar planets, but more than that, now we know that planets can exist around extremely lightweight stars as well (another link here). Thanks to this planet called VB 10b that has been discovered orbiting a star barely large enough to be called one - an M dwarf called VB 10. What's important about this though is that M dwarfs are the most common stars out there, making up over 75% of all main sequence stars, and now we're sure that even the smallest of these stars can have fairly large planets.
VB 10 is one-twelfth the mass of the Sun, and for comparison the famous red dwarf Gliese 581 (the one with all the super-Earth planets) is one-third the mass of the Sun, so this one is only a quarter the mass of even the red dwarf Gliese 581.
As for the planet itself, it's six times the mass of Jupiter, so one percent the mass of the star it orbits. Though it's located at about the same distance as Mercury (around this star that's already beyond the habitability zone) its high mass means that it has quite a bit of internal heating and thus isn't cold.