Anatomy of a super-Earth (original) (raw)

They are out there, and they are unlike anything previously discovered in the galaxy. Dubbed “super-Earths” because of their size, these planets are the first predominantly rocky worlds found outside our solar system.

Big deal? You bet. The discovery of this new class of planet takes us a significant step closer to finding other Earth-like worlds that might be suitable for life. It also sheds new light on the physics of planetary formation. Indeed, the race to find Earth’s bigger cousins is hotting up: a French-led space telescope called Corot is scheduled to launch later this month, with the promise of detecting more of these mysterious worlds.

What is most interesting is not that super-Earths are big, but that they are relatively small. Since the discovery in 1995 of a Jupiter-sized planet around the star 51 Pegasi, astronomers have located more than 200 extrasolar planets. Until last year, all had been classified as gas giants like Jupiter, Saturn, Uranus and Neptune – most of them hundreds of times the Earth’s mass. (A few were originally mislabelled super-Earths but have since been judged Neptune-class.) Now, thanks to more sensitive instruments and better analytical techniques, researchers are detecting smaller planets which, crucially, should be more Earth-like.

So far we know of just two super-Earths (see Diagram). They are less than half the mass of any previously known extrasolar planet, which is why researchers are confident they have crossed the threshold from gas giants to rocky worlds. Although no telescope is yet powerful enough to reveal their surfaces, astronomers have plenty of ideas about what they might look like.

The first was discovered…