Gliese 581b
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Gliese 581b is an extrasolar planet orbiting the star Gliese 581.
Discovery
The planet was discovered by a team of French and Swiss astronomers, who announced their findings on November 30 2005 as a discovery of one of the smallest extrasolar planets ever found, with one conclusion being that planets may be more common around the smallest stars. It was the fifth planet found around a red dwarf star (after Gliese 876's planets and Gliese 436 b).
The planet was discovered using the HARPS instrument, with which they found the host star to have a wobble that implied the existence of the planet.
The astronomers published their results in a Letter to the Editor of Astronomy and Astrophysics.[1]
Orbit and mass
Gliese 581 b is at minimum about 16 times the Earth's mass, similar to Neptune's mass. It does not transit its star, implying that its inclination is under 88.1 degrees.[2] 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.[3] For Gliese 581 b, the upper bound of its mass is about 90 times the mass of the Earth, similar to that of Saturn.[4] At this mass it must be held together with a central heavy-element core like Saturn and maybe even HD 149026 b.
It is rather close to Gliese 581 and completes a full orbit in only 5.4 days at a mean distance of about 6 million kilometres (0.041 AU). By comparison, Mercury is at a distance of 58 million kilometres (0.387 AU) and completes an orbit in 88 days.
Characteristics
Gliese 581 b is about 0.04 AU from its sun. It is likely close to Gliese 436 b in mass, temperature, and (with Gliese 876 d) susceptibility to solar effects such as coronal mass ejection. Since Gliese 581 b does not transit, nothing more can be said of it yet. At the least, given that Gliese 581 b orbits alongside two other planets and that Gliese 436 b (thus far) stands alone, their formation must have differed.
References
- ^ Bonfils; et al. (2005). "The HARPS search for southern extra-solar planets, VI. A Neptune-mass planet around the nearby M dwarf Gl 581". Astronomy and Astrophysics. 443: L15–L18.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ Mercedes Lopez-Morales, Nidia I. Morrell, R. Paul Butler, Sara Seager (2006). "Limits to Transits of the Neptune-mass planet orbiting Gl 581". arXiv:0609255v1 [astro-ph].
{{cite arXiv}}: Check|arxiv=value (help)CS1 maint: multiple names: authors list (link) - ^ Beust, H.; et al. (2008). "Dynamical evolution of the Gliese 581 planetary system". Astronomy and Astrophysics. 479 (1): 277–282. doi:10.1051/0004-6361:20078794. Retrieved 2008-08-20.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ Dividing the m sin i of 15.82, by "Sin(10/180 * PI)" on a radian-configured processor, yields 91.1.
See also
Other members of the system:
Related topics: