HD 189733 b
HD 189733 b is an exoplanet in the constellation of Vulpecula approximately 64.5 light-years (19.8 parsecs) away from the Solar System. Astronomers in France discovered the planet orbiting the star HD 189733 on October 5, 2005, by observing its transit across the star's face. With a mass 11.2% higher than that of Jupiter and a radius 11.4% greater, HD 189733 b orbits its host star once every 2.2 days at an orbital speed of 152.0 kilometers per second (152,000 meters per second; 340,000 miles per hour), making it a hot Jupiter with poor prospects for extraterrestrial life.
Jupiter and HD 189733 b compared | |
| Discovery | |
|---|---|
| Discovered by | Bouchy et al. |
| Discovery site | Haute-Provence Observatory |
| Discovery date | October 5, 2005 |
Detection method | Doppler spectroscopy Transit |
| Orbital characteristics | |
Semi-major axis | 0.03100 ± 0.0006 AU (4,638,000 ± 90,000 km) |
| Eccentricity | <0.0039 |
Orbital period (sidereal) | 2.218575200(77) d 53.2458048 h |
Average orbital speed | 152.0 km/s |
| Inclination | 85.580°±0.060° |
| Semi-amplitude | 201.3±1.6 m/s |
| Star | HD 189733 |
| Physical characteristics | |
Mean radius | 1.138±0.027 RJ |
| Mass | 1.123±0.045 MJ |
Mean density | 0.943+0.081 −0.072 g/cm3 |
Surface gravity | 21.5 m/s2 (2.2 g) |
| Albedo | 0.40±0.12 (290–450 nm) <0.12 (450–570 nm) 0.076±0.016 (geometric) |
| Temperature | 1,192±9 K (919 °C; 1,686 °F) 1,490±68 K (1,220 °C; 2,220 °F) |
The closest transiting hot Jupiter to Earth, HD 189733 b has been the subject of close atmospheric observation. Scientists have studied it with high- and low-resolution instruments, both from the ground and from space. Researchers have found that the planet's weather includes raining molten glass. HD 189733 b was also the first exoplanet to have its thermal map constructed, possibly to be detected through polarimetry, its overall color determined (deep blue), its transit viewed in the X-ray spectrum, and to have carbon dioxide confirmed as being present in its atmosphere.
In July 2014, NASA announced the discovery of very dry atmospheres on three exoplanets that orbited Sun-like stars: HD 189733 b, HD 209458 b, and WASP-12b.