Planetary System
HD 209458 b is an extrasolar planet that orbits the Sun-like star HD 209458 in the constellation Pegasus. Spectroscopic studies first revealed the presence of a planet around HD 209458 on November 5, 1999. The planet is now under even more public scrutiny with the announcement that its atmosphere contains water vapor. Astronomers had made careful photometric measurements of several stars known to be orbited by planets, in the hope that they might observe a dip in brightness caused by the transit of the planet across the star's face. This would require the planet's orbit to be inclined such that it would pass between the Earth and the star, and previously no transits had been detected.
Travis Barman at Lowell Observatory in Flagstaff, Arizona analyzed the emission spectrum of this planet, and believes that its atmosphere contains water, although previous research suggests that the atmosphere is composed mostly of silicate clouds.
| Companion |
Mass | Semimajor axis |
Orbital period |
Eccentricity | Radius |
|---|---|---|---|---|---|
| b | 0.69 ± 0.05 MJ | 0.045 | 3.52474541 ± 0.00000025 | 0.00 | — |
Read more about this topic: HD 209458
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