Gliese 777 Ab
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| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
| Orbital elements | ||
| Semimajor axis | (a) | 3.92 AU |
| Eccentricity | (e) | 0.36 ± 0.03 |
| Orbital period | (P) | 2891 ± 85 d |
| Angular distance | (θ) | 246.696 mas |
| Longitude of periastron |
(ω) | 12.4 ± 9.3° |
| Time of periastron | (T0) | 2,450,628.1 ± 99.8 JD |
| Semi-amplitude | (K) | 23.5 ± 0.5 m/s |
| Physical characteristics | ||
| Mass | (m) | >1.502 ± 0.13 MJ |
| Discovery information | ||
| Discovery date | June 19, 2002 | |
| Discoverer(s) | Mayor et al. | |
| Detection method | Doppler Spectroscopy | |
| Discovery site | Geneva Extrasolar Planet Search Team in France |
|
| Discovery status | Published | |
Gliese 777 Ab is a gas giant planet orbiting the star Gliese 777 A. It was discovered on June 19, 2002 by the Geneva Extrasolar Planet Search Team using the radial velocity method that has been used to detect most of the planets found so far. The planet is at least one half more massive than Jupiter but roughly the same size as Jupiter. Because the inclination of the planet's orbit is not known, the true mass is unknown. But it is unlikely to be much more than the given minimum mass.
The planet has one of the longest orbits currently known for an extrasolar planet. The planet's mean distance from the star is close to the distance between Jupiter and the Sun. However, unlike Jupiter it has a eccentric orbit. At periastron the distance between the planet and the star is only 2.51 AU and at apoastron the distance is as much as 5.33 AU (compared to our Solar system, distance from Sun to the inner asteroid belt and from Sun to just beyond the orbit of Jupiter). The gravitational influence of the red dwarf companion may have caused the eccentricity of the planet.
The signal produced by the planet is very weak and the eccentricity was originally supposed to be very circular which led to speculations of a very Jupiter-like planet. Fortunately, the inner system should be stable for Earth-like planets.
[edit] References
- Naef et al. (2003). "The ELODIE survey for northern extra-solar planets II. A Jovian planet on a long-period orbit around GJ 777 A". Astronomy and Astrophysics 410: 1051–1054.
