spacetoday.net: Exoplanet found to be made of "hot ice"

Posted: Fri, May 18, 2007, 6:40 AM ET (1040 GMT)
Gliese 436 exoplanet illustration (NASA)

Astronomers this week said that a previously-discovered extrasolar planet appears to be made of exotic forms of ice that can exist at high temperatures. Swiss astronomers studied the exoplanet, orbiting close to the star GJ 436 30 light-years away, as it transited across the star's disk as seen from Earth. Those observations allowed astronomers to estimate its size and, combined with previous measurements of its mass, the exoplanet's density. Astronomers found that the planet is too compact to be a gaseous "hot Jupiter", like many other exoplanets found near their parent stars, but not dense enough to be a rocky planet like the Earth. Instead, they suggest that the planet may have any icy composition, with an atmosphere of water vapor and other gases, but an interior that stays icy at high pressures, deposits temperatures of hundreds of degrees Celsius.