vorenhutz

they don’t know exactly what the density of the gliese 581 planets are. mass measured by radial velocity is really a minimum mass, the actual mass depends on unknown orbital parameters… and there’s no way to measure the radius. the composition is pretty much an educated guess. radial velocity is pretty good at detecting planets, not so good at characterising them.

on the other hand corot 7-b was detected by transit, a method where mass and radius are directly measurable and an exact density can be calculated.

Geoff G

There ae so many extrasolar planets being discovered nowadays that each discoverer has to try hard to differentiate their discovery from everybody else’s. Sometimes they conveniently forget the claims made for earlier discoveries.

Little Raven

The media has a hard time keeping track of this stuff. Most mainstream journalists don’t know enough about science to get it right most of the time.

Also, ‘solid water’ would be ice. Gliese 581 has several rocky planets, but only 581d is in the star’s habitable zone (the distance from the star where liquid water could exist, instead of it all freezing or evaporating). It’s entirely possible that this planet has both liquid and solid water. But its mass is 8 times that of Earth, so the gravity there would be pretty heavy.

All of Gliese 581′s other planets are too close to the star to have liquid or solid water. Any water there would evaporate from the heat.

chris

Yeah, the exoplanet COROT-7b is orbiting the star COROT-7. And the planet Gliese 581 e is the exoplanet orbiting the star Gliese 581. Both of these planets are thought to be rocky planets like Earth but COROT is a special case; scientists believe that the planets composition by equal parts water and rocky material. It was hypothesized that COROT may have been a “water planet” were it not so close to its sun which has caused any water on/in the planet to exist primarily as water vapor.