Gliese 581: Difference between revisions
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At least three [[planets]] are believed to be orbiting this [[star]]. One, about [[Neptune]]-sized, was discovered in [[2005]].<ref name="bonfils">{{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 }}</ref> Another, having an estimated radius 1.5 times that of Earth, was discovered in [[2007]].<ref name="udry">{{cite journal | url=http://obswww.unige.ch/~udry/udry_preprint.pdf |author=Udry et al.|title=The HARPS search for southern extra-solar planets, XI. An habitable super-Earth (5 M<sub>⊕</sub>) in a 3-planet system |journal = [[Astronomy and Astrophysics]] | volume=preprint | year=2007 | pages=preprint }}</ref> The latter is doubly notable, as it is the first planet |
At least three [[planets]] are believed to be orbiting this [[star]]. One, about [[Neptune]]-sized, was discovered in [[2005]].<ref name="bonfils">{{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 }}</ref> Another, having an estimated radius 1.5 times that of Earth, was discovered in [[2007]].<ref name="udry">{{cite journal | url=http://obswww.unige.ch/~udry/udry_preprint.pdf |author=Udry et al.|title=The HARPS search for southern extra-solar planets, XI. An habitable super-Earth (5 M<sub>⊕</sub>) in a 3-planet system |journal = [[Astronomy and Astrophysics]] | volume=preprint | year=2007 | pages=preprint }}</ref> The latter is doubly notable, as it is the first low-mass planet discovered in the [[habitable zone]] of another star, and it also may be as few as five times as massive as the [[Earth]] with a potentially similar composition, making it by far the most "earthlike" [[exoplanet]] discovered anywhere to date. Observations of the star also revealed the possibility of a third planet with a mass of roughly 8 Earths and an orbit of 84 Earth days. |
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=== Gliese 581 b === |
=== Gliese 581 b === |
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Revision as of 22:03, 28 April 2007
 | This article documents a current event. Information may change rapidly as the event progresses, and initial news reports may be unreliable. The latest updates to this article may not reflect the most current information. (April 2007) |
File:Phot-22a-07-normal.jpg Artist's impression of the Gliese 581 system. Credit: ESO. | |
| Observation data Epoch J2000 Equinox J2000 | |
|---|---|
| Constellation | Libra |
| Right ascension | 15h 19m 26.8250s |
| Declination | −07° 43′ 20.209″ |
| Apparent magnitude (V) | 10.56 |
| Characteristics | |
| Spectral type | M3V |
| B−V color index | 1.60 |
| Variable type | BY Draconis variable |
| Astrometry | |
| Radial velocity (Rv) | -9.5 km/s |
| Proper motion (μ) | RA: -1224.55 mas/yr Dec.: -99.51 mas/yr |
| Parallax (π) | 159.52 ± 2.27 mas |
| Distance | 20.4 ± 0.3 ly (6.27 ± 0.09 pc) |
| Absolute magnitude (MV) | 11.56 |
| Details | |
| Mass | 0.31[1] M☉ |
| Radius | 0.38[1] R☉ |
| Luminosity | 0.013[2] L☉ |
| Temperature | 3,480[3] K |
| Metallicity | [M/H] = -0.33[3] |
| Age | 4.3 × 109[1] years |
| Other designations | |
| Database references | |
| SIMBAD | data |
Gliese 581 is an M2.5V red dwarf star located 20.40 light years away from Earth. It is about two degrees north of Beta Librae, the brightest star in the constellation Libra. Its mass is estimated to be approximately a third that of the Sun.
Observations suggest that the star has at least three planets.
Star
The name Gliese 581 refers to the Star catalogue of nearby stars by Wilhelm Gliese. Other names of this star include BD-07° 4003 (BD catalogue, first known publication) and HO Librae (variable star designation). It does not have an individual name such as Sirius or Procyon.
Gl 581 is classified as a BY Draconis variable, which is a star that shows a fluctuating luminosity with periods ranging from hours to several months. These light changes are caused by variations in the surface brightness of the photosphere combined with the axial rotation of the star.[4] Gl 581 undergoes long-term changes in luminosity, with the brightness varying by up to half a magnitude.[5] (Short-term variability is at most 0.006 magnitudes.)[2]
An M-class dwarf star such as Gliese 581 has a much lower mass than the Sun, causing the core region of the star to burn hydrogen at a significantly lower rate. As a result, this star has only 1.3% of the Sun's total luminosity, and a planet would need to be situated much closer to this star in order to receive a comparable amount of energy as the Earth. The region of space around a star where a planet would receive roughly the same energy as the Earth is sometimes termed the "Goldilocks Zone", or, more-accurately, the habitable zone.
Planetary system
At least three planets are believed to be orbiting this star. One, about Neptune-sized, was discovered in 2005.[2] Another, having an estimated radius 1.5 times that of Earth, was discovered in 2007.[6] The latter is doubly notable, as it is the first low-mass planet discovered in the habitable zone of another star, and it also may be as few as five times as massive as the Earth with a potentially similar composition, making it by far the most "earthlike" exoplanet discovered anywhere to date. Observations of the star also revealed the possibility of a third planet with a mass of roughly 8 Earths and an orbit of 84 Earth days.
Gliese 581 b
Gliese 581 b was the fifth planet to be discovered around a red dwarf star. This inner planet is 16 times as massive as Earth (similar to Neptune's mass) and completes a full orbit of Gliese 581 in only 5.4 days.
Gliese 581 c
Gliese 581 c is believed to be a rocky planet of 50% greater radius than Earth and about five times Earth's mass, orbiting within the habitable zone of its parent star. The mean surface temperature has been estimated to lie between -3 °C (for a Venus-like albedo) and 40 °C (for an Earth-like albedo),[6] suggesting the possibility of liquid water on a solid surface. However, given the closer-orbiting Neptune-mass planet, the system has undergone planetary migration and Gliese 581 c may have formed beyond the frost line, with a composition similar to icy bodies like Ganymede.[citation needed] Gliese 581 c completes a full orbit in just under 13 days. Gliese 581 c orbits one of the hundred closest stars to Earth, which has led some to suggest that Earth-like planets are much more common than previously speculated.[7]
Gliese 581 d
Gliese 581 d is about eight times as massive as the Earth and orbits its sun in 84 days.
See also
References
- ^ a b c "Star: Gl 581". Extrasolar Planets Encyclopaedia. Retrieved 2007-04-26.
- ^ a b c 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) - ^ a b Bean, J. L.; Benedict, G. F.; Endl, M. (2006). "Metallicities of M Dwarf Planet Hosts from Spectral Synthesis". The Astrophysical Journal. 653 (1): L65–L68. Retrieved 2007-02-04.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ "BY Draconis variables". Centre de Données astronomiques de Strasbourg. Retrieved 2007-04-27.
- ^ Lopez-Morales, M.; Morrell, N. I.; Butler, R. P.; Seager, S. (2006). "Limits to Transits of the Neptune-mass planet orbiting Gl 581". Publications of the Astronomical Society of the Pacific. 118: 1506–1509. Retrieved 2007-04-27.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ a b Udry; et al. (2007). "The HARPS search for southern extra-solar planets, XI. An habitable super-Earth (5 M⊕) in a 3-planet system" (PDF). Astronomy and Astrophysics. preprint: preprint.
{{cite journal}}: Explicit use of et al. in:|author=(help) - ^ 20 light years away, the most Earthlike planet yet IHT.com
- "Major Discovery: New Planet Could Harbor Water and Life"
- Sol Station: Gliese 581 / HO Librae
- BBC News report
- CTV News Report
