Instead of a rocky world like Earth, HD 189733b is large, about 1.15 times the mass of Jupiter. Located just 4.5 million km from its star, it orbits it in 2.2 days. In comparison, Earth is 150 million km from the Sun; even Mercury, the innermost planet, is 70 million km away.
Astronomers classify such worlds as ‘hot jupiters’. These planets tend to have extensive atmospheres because heat from the nearby star gives them energy to expand. HD 189733b is no exception; its diameter is 1.25 times that of Jupiter.
HD 189733b’s atmospheric temperature is about 1000 Kelvin (a little more than 700°C) or higher, implying that the significant amounts of water vapour in the atmosphere cannot condense to fall as rain or form clouds. The temperature would have to be about five times lower to form clouds of water vapour or rain.
Thursday, July 12, 2007
Astronomers have found evidence of water vapour in the atmosphere of a planet which orbits a star some 63 light years away, but it resides too close to its star to have any chances of life existing on it. From ESA press release:
Posted by I.Z. Reloaded at 11:22 AM
This work is licensed under a Creative Commons Attribution-Noncommercial 3.0 Singapore License.