Gliese 581 b

Planetbox begin
name = Gliese 581bPlanetbox star
star = Gliese 581
constell = Libra
RA = RA|15|19|26
DEC = DEC|−07|43|20
dist_ly = 19.9
dist_pc = 6.12
class = M2.5V Planetbox orbit
semimajor = 0.04061cite journal |author=Udry, S., Bonfils, X., Delfosse, X., "et al." |year=2007| journal=Astronomy and Astrophysics| title=The HARPS search for southern extra-solar planets. XI. Super-Earths (5 and 8 M⊕) in a 3-planet system| volume=469| page=L43]
eccentricity = 0.01374 ± 0.01405
period = 5.36843 ± 0.00031
ang_dist = 6.55
t_peri = 2,451,299.99
semi-amp = 12.42Planetbox character
mass_earth = >15.82 ± 0.25 Planetbox discovery
discovery_date = August 22, 2005
announced November 30, 2005
discoverers = X. Bonfils, T. Forveille, X. Delfosse, S. Udry, M. Mayor, C. Perrier, F. Bouchy, F. Pepe, D. Queloz, J.-L. Bertaux
discovery_method = Doppler Spectroscopy
discovery_status=Published

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. [cite journal | url=http://www.edpsciences.org/papers/aa/full/2005/45/aahh223/aahh223.html |author=Bonfils et al.|title=The HARPS search for southern extra-solar planets, VI. A Neptune-mass planet around the nearby M dwarf Gl 581 |journal = Astronomy and Astrophysics | volume=443 | year=2005 | pages=L15–L18 ]

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. [cite arXiv | title=Limits to Transits of the Neptune-mass planet orbiting Gl 581 | author=Mercedes Lopez-Morales, Nidia I. Morrell, R. Paul Butler, Sara Seager |year=2006|class=astro-ph |eprint=0609255v1] 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. [cite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2008A%26A...479..277B&db_key=AST&nosetcookie=1|author=Beust, H. et al.|title=Dynamical evolution of the Gliese 581 planetary system|journal=Astronomy and Astrophysics|volume=479|issue=1|year=2008|pages=277–282|doi=10.1051/0004-6361:20078794|accessdate=2008-08-20] For Gliese 581 b, the upper bound of its mass is about 90 times the mass of the Earth, similar to that of Saturn. [Dividing the m sin i of 15.82, by "Sin(10/180 * PI)" on a radian-configured processor, yields 91.1.] 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

ee also

Other members of the system:
*Gliese 581
*Gliese 581 c
*Gliese 581 dRelated topics:
*Gliese 229
*Gliese 436 b
*Gliese 876 b
*Gliese 876 c
*Gliese 876 d

External links

* [http://www.eso.org/outreach/press-rel/pr-2005/pr-30-05.html ESO: The Dwarf that Carries a World]
* [http://www.solstation.com/stars/gl581.htm SolStation: Gliese 581 / HO Librae]
* [http://exoplanet.eu/star.php?st=Gl+581 Extrasolar Planets Encyclopaedia: Gl 581]