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| Extrasolar planet | List of extrasolar planets | |
|---|---|---|
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| Parent star | ||
| Star | Gliese 581 | |
| Constellation | Libra | |
| Right ascension | (α) | 15h 19m 26s |
| Declination | (δ) | −07° 43′ 20″ |
| Distance | 20.3 ly (6.2 pc) |
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| Spectral type | M3V | |
| Orbital elements | ||
| Semimajor axis | (a) | 0.2525 ± 0.013[1] AU |
| Eccentricity | (e) | 0.12118 ± 0.12034[1] |
| Orbital period | (P) | 83.22730 ± 0.65845[1] d |
| Physical characteristics | ||
| Mass | (m) | >7.804 ± 0.69[1] M⊕ |
| Discovery information | ||
| Discovery date | 24 April 2007 | |
| Discoverer(s) | Udry et al. | |
| Detection method | Radial velocity | |
| Discovery site |  Switzerland |
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| Discovery status | Published[1] | |
Gliese 581 d (pronounced /ˈgliːzə/) is an extrasolar planet approximately 20 light-years away in the constellation of Libra. Because of its mass, the planet is classified as a super-Earth planet. Because the planet orbits in the outer edge of its parent star's habitable zone, it is thought that the planet may be similar to Earth.
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Discovery
The planet was discovered by the team of Stéphane Udry of the Geneva Observatory in Switzerland using the HARPS instrument on the European Southern Observatory 3.6 meter telescope in La Silla, Chile on 24 April 2007. Udry's team employed the radial velocity technique, in which the size and mass of a planet are determined based on the small perturbations it induces in its parent star’s orbit via gravity.
The team is confident that the planet exists but recognizes that unlikely events could mimic its existence. They believe the issue will be settled by upcoming studies.
Dynamical simulations of the Gliese 581 system assuming that the orbits of the three planets are coplanar show that the system becomes unstable if its component masses are so high as to correspond to an overall inclination angle of 10° or less.[2] For Gliese 581 d, the upper bound of its mass must be half that of 581 b; that is, 581 d's maximum is 45 Earth masses.[3] At this mass it must be held together with a central heavy-element core like Saturn and maybe even HD 149026 b.
Climate and habitability
Although Gliese 581 d orbits outside the theoretical habitable zone of its star, scientists surmise that conditions on the planet may be conducive to supporting life.[4][5] Scientists originally believed that Gliese 581 d would be too cold for liquid water to exist, and therefore could not support life in forms as existing on Earth. However, since Earth's temperature would be about -19°C without any greenhouse gases,citation needed and due to a theorized greenhouse effect of Gliese 581 d, research now suggests that atmospheric conditions on the planet could create temperatures at which liquid water can exist, and therefore the planet may be capable of supporting life.citation needed
References
- ^ a b c d e Udry, S.; Bonfils, X.; Delfosse, X.; Forveille, T.; Mayor, M.; Perrier, C.; Bouchy, F.; Lovis, C.; Pepe, F.; Queloz, D.; Bertaux, J.-L. (2007). "The HARPS search for southern extra-solar planets. XI. Super-Earths (5 and 8 M⊕) in a 3-planet system". Astronomy and Astrophysics 469 (3): L43 – L47. doi:. Retrieved on 2008-08-18.
- ^ Beust, H. et al. (2008). "Dynamical evolution of the Gliese 581 planetary system". Astronomy and Astrophysics 479 (1): 277–282. doi:. Retrieved on 2008-08-20.
- ^ Dividing the m sin i by "Sin(10/180 * PI)" on a radian-configured processor.
- ^ SPACE.com - Hopes Dashed for Life on Distant Planet
- ^ von Bloh, W.; Bounama, C.; Cuntz, M.; Franck, S.. "The Habitability of Super-Earths in Gliese 581". Astronomy & Astrophysics 476: 1365 – 1371. doi:. Retrieved on 2008-08-18.
External links
- "Notes for planet Gl 581 d". The Extrasolar Planets Encyclopaedia. Retrieved on 2008-07-15.
