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Gliese 581 g

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Gliese 581 g

Extrasolar planet		List of extrasolar planets
The orbits of planets in the Gliese 581 system compared to those of our own solar system
Parent star
Star		Gliese 581
Constellation		Libra
Right ascension	(α)	15h 19m 26s
Declination	(δ)	−07° 43′ 20″
Apparent magnitude	(mV)	10.55
Distance		20.3 ± 0.3 ly (6.2 ± 0.1 pc)
Spectral type		M3V
Mass	(m)	0.31 M☉
Radius	(r)	0.29 R☉
Temperature	(T)	3480 ± 48 K
Metallicity	[Fe/H]	-0.33 ± 0.12
Age		7 – 11 Gyr
Orbital elements
Semimajor axis	(a)	0.146[1] AU
Orbital period	(P)	36.6[1] d
Physical characteristics
Minimum mass	(m sin i)	3.1 – 4.3[1] M⊕
Radius	(r)	1.3 – 2[1] R⊕
Surface gravity	(g)	1.1 – 1.7[1] g
Discovery information
Discovery date		September 29, 2010
Discoverer(s)		Steven S. Vogt et al.
Detection method		Radial Velocity
Discovery site		Keck Observatory, Hawaii
Discovery status
Database references
Extrasolar Planets Encyclopaedia		data
SIMBAD		data

Gliese 581 g (pronounced /ˈɡliːzə/) or Gl 581 g,^[2] is an extrasolar planet, orbiting the red dwarf star Gliese 581, approximately 20.5 light-years^[3] away from Earth in the constellation of Libra. It is the sixth planet discovered in the Gliese 581 planetary system and the fourth in order from the star. The planet was discovered by the Lick-Carnegie Exoplanet Survey after more than a decade's worth of observations. Despite the Gliese 581 system having a "somewhat checkered history of habitable planet claims," ^[1] results from the study imply that the planet is located in the middle of the "Goldilocks", or habitable zone of its parent star, where the existence of liquid water is considered a strong possibility.^[4] The discovery of Gliese 581 g was announced in late September 2010,^[1] and is believed to be the first Goldilocks planet ever found, the most Earth-like planet, and the best exoplanet candidate with the potential for harboring life found to date.^[5]

Contents [hide] 1 Discovery 2 Habitability 3 Implications 4 See also 5 Notes and references 6 External links

Discovery

The planet was detected by a team of astronomers in the Lick-Carnegie Exoplanet Survey, led by principal investigator Steven Vogt, professor of astronomy and astrophysics at the University of California, Santa Cruz and co-investigator Paul Butler of the Carnegie Institution of Washington. The discovery was made using radial velocity measurements combining 11 years of data from the HIRES instrument of the Keck 1 telescope and the HARPS instrument of ESO's 3.6m telescope at La Silla Observatory.^[1][6]

The planet is believed to have a mass of 3.1 to 4.3 times that of the Earth and a radius of 1.3 to 2 times that of Earth. It has an orbital period of just under 37 days, orbiting at a distance of 0.146 AU from its parent star.^[1]

The Lick-Carnegie team explained the results of their research in a paper published in the Astrophysical Journal.

Habitability

The orbits of the Gliese 581 planetary system, with circular orbits, excluding outermost planet f.

In an interview with Lisa-Joy Zgorski of the National Science Foundation, Steven Vogt was asked what he thought about the chances of life existing on Gliese 581 g. Vogt was optimistic: "I'm not a biologist, nor do I want to play one on TV. Personally, given the ubiquity and propensity of life to flourish wherever it can, I would say that, my own personal feeling is that the chances of life on this planet are 100%. I have almost no doubt about it."^[7]

Despite other planets between Gliese 581g and the parent star not being tidally locked (Gliese 581 d eccentricity is 0.38 [1]) Gliese 581 g's size combined with proximity make it likely to be tidally locked to Gliese 581. Just as our moon always presents the same face to the Earth, the length of Gliese 581 g's sidereal day would then precisely match the length of its year.^[1][8] Tidal locking would mean the planet would have no axial tilt and therefore no seasonality in any normal sense of the word. Its mass indicates that it is probably a rocky planet with a definite surface and that it has enough gravity to hold on to an atmosphere, likely one that is denser than Earth's.^[1] Researchers have estimated that the global average surface temperature of the planet averages between −31 to −12 degrees Celsius (−24 and 10 degrees Fahrenheit).^[9] With one side of the planet always facing the star, temperatures would range from blazing hot in the light side to freezing cold in the dark side, with continuous Earth-like temperatures imaginable along the terminator (the area between the bright and the dark side), informally known as the twilight zone.

Theoretical models of tidally locked worlds predict that under some conditions, volatile compounds such as water and carbon dioxide, if present, might evaporate in the scorching heat of the sunward side, migrate to the cooler night side, and condense to form ice caps. Over time, the entire atmosphere might freeze into ice caps on the night side of the planet. However, the amounts of water and carbon dioxide present on the surface of Gliese 581 g are unknown. Alternatively, an atmosphere massive enough to be stable would circulate the heat more evenly, allowing for a wider habitable area on the surface.^[10] For example, Venus has a solar rotation rate approximately 117 times slower than Earth's, producing prolonged days and nights. Despite the uneven distribution of sunlight over time intervals shorter than several months, unilluminated areas of Venus are kept almost as hot as the day side by globally circulating winds.^[11]

Implications

Scientists have monitored only a relatively small number of stars in the search for exoplanets. The discovery of a potentially habitable planet like Gliese 581 g so early in the search might mean that habitable planets are more widely distributed than had been previously believed. According to Vogt, the discovery "implies an interesting lower limit on the fraction of stars that have at least one potentially habitable planet as there are only ~116 known solar-type or later stars out to the 6.3 parsec distance of Gliese 581."^[12] With the discovery of Gliese 581 g, the ratio of systems with habitable planets could be 10–20%^[1] with "potentially billions" of Earth-like planets in our Milky Way galaxy alone.^[13]

See also

	Astronomy portal
	Space portal

• Habitability and climate of Gliese 581 c
• Habitability of red dwarf systems
• Climate of Mars

Notes and references

1. ^ ^{a b c d e f g h i j k l} Vogt, Steven S.; Butler, R. Paul; Rivera, Eugenio J.; Haghighipour, Nader; Henry, Gregory W.; Williamson, Michael H. (2010-09-29). "The Lick-Carnegie Exoplanet Survey: A 3.1 M_Earth Planet in the Habitable Zone of the Nearby M3V Star Gliese 581". accepted by the Astrophysical Journal. http://arxiv.org/abs/1009.5733. Retrieved 2010-09-29. 
2. ^ Borenstein, Seth (2010-09-29). "Could 'Goldilocks' planet be just right for life?". Associated Press. http://hosted.ap.org/dynamic/stories/U/US_SCI_NEW_EARTHS?SITE=ILMOL&SECTION=HOME&TEMPLATE=DEFAULT. Retrieved September 30, 2010. 
3. ^ About 193 trillion kilometres
4. ^ Shiga, David (2010-09-29). "Found: first rocky exoplanet that could host life". New Scientist. http://www.newscientist.com/article/dn19519-found-first-rocky-exoplanet-that-could-host-life.html. Retrieved September 30, 2010. 
5. ^ "Just-right planet that can support life detected". Reuters, USA. September 29, 2010. http://www.reuters.com/article/idUSTRE68S5XB20100929. Retrieved September 30, 2010. 
6. ^ Alleyne, Richard (September 30, 2010). "Gliese 581g the most Earth like planet yet discovered". The Daily Telegraph. http://www.telegraph.co.uk/science/space/8033124/Gliese-581g-the-most-Earth-like-planet-yet-discovered.html. Retrieved September 30, 2010. 
7. ^ NSF. Press Release 10-172 - Video. Event occurs at 41:25-42:31. See Overbye, Dennis (2010-09-29). "New Planet May Be Able to Nurture Organisms". The New York Times'. http://www.nytimes.com/2010/09/30/science/space/30planet.html?_r=1. Retrieved September 30, 2010. 
8. ^ "Astronomers Find Most Earth-like Planet to Date". Science, USA. September 29, 2010. http://news.sciencemag.org/sciencenow/2010/09/astronomers-find-most-earth-like.html. Retrieved September 30, 2010. 
9. ^ Stephens, Tim (2010-09-29). "Newly discovered planet may be first truly habitable exoplanet". University News & Events. University of California, Santa Cruz. http://news.ucsc.edu/2010/09/planet.html. 
10. ^ Alpert, Mark (2005-11-07). "Red Star Rising". Scientific American. http://www.sciam.com/article.cfm?chanID=sa004&articleID=000CC344-B043-1353-AF3383414B7FFE9F. Retrieved 2007–04–25. 
11. ^ Ralph D Lorenz, Jonathan I Lunine, Paul G Withers, Christopher P. McKay (2001). "Titan, Mars and Earth: Entropy Production by Latitudinal Heat Transport" (PDF). Ames Research Center, University of Arizona Lunar and Planetary Laboratory. http://sirius.bu.edu/withers/pppp/pdf/mepgrl2001.pdf. Retrieved 2007-08-21. 
12. ^ Vogt 2010, pp.32-33. For more information, see Turnbull, Margaret C.; Tarter, Jill C. (Mar., 2003). "Target Selection for SETI: 1. A Catalog of Nearby Habitable Stellar Systems". The Astrophysical Journal (Institute of Physics Publishing). http://arxiv.org/abs/astro-ph/0210675. 
13. ^ Berardelli, Phil (2010-09-29). "Astronomers Find Most Earth-like Planet to Date". AAAS. http://news.sciencemag.org/sciencenow/2010/09/astronomers-find-most-earth-like.html. Retrieved September 30, 2010. 

External links

• National Science Foundation. "Steven Vogt and Paul Butler lead a team that discovered the first potentially habitable exoplanet". http://www.nsf.gov/news/news_videos.jsp?cntn_id=117765&media_id=68454&org=NSF. "Video: Steven Vogt of UC Santa Cruz and UC Observatories and Paul Butler of the Carnegie Institution of Washington join NSF's Lisa-Joy Zgorski to announce the discovery of the first exoplanet that has the potential to support life." 
• "NASA and NSF-Funded Research Finds First Potentially Habitable Exoplanet". Release 10-237. NASA. 2010-09-29. http://www.nasa.gov/home/hqnews/2010/sep/HQ_10-237_Exoplanet_Findings.html. 

[hide] v • d • e The Gliese 581 system Star Gliese 581 Planets Gliese 581 e • Gliese 581 b • Gliese 581 c • Gliese 581 g • Gliese 581 d • Gliese 581 f Book:Gliese 581 • Category:Gliese 581 • Portal:Astronomy

[show] v • d • e Nearest star systems Star systems (including brown dwarf systems) within 30 light-years from Earth. [show]   0 - 5 ly G V* (Yellow) Solar System (1s, 8p) • Alpha Centauri (3s: Alpha¹ Centauri • Alpha² Centauri • Proxima Centauri) [show]   5 - 10 ly A V* (White) Sirius (2s) M V* (Red dwarf) Barnard's Star system (1s) • Wolf 359 (1s) • Lalande 21185 (1s) • BL/UV Ceti (2s) • Ross 154 (1s) [show]   10 - 15 ly F V* (Yellow-white) Procyon (2s) G V* (Yellow) Tau Ceti (1s) K V* (Orange) Sadira (1s, 2p: planet b • planet c) • 61 Cygni (2s) • Epsilon Indi (1s, 2bd) M V* (Red dwarf) Ross 248 (1s) • Lacaille 9352 (1s) • Ross 128 (1s) • EZ Aquarii (3s) • Struve 2398 (2s) • Groombridge 34 (2s) • DX Cancri (1s) • GJ 1061 (1s) • YZ Ceti (1s) • Luyten's Star system (1s) • Teegarden's Star system (1s) • SCR 1845-6357 (1s, 1bd) • Kapteyn's Star system (1s) • Lacaille 8760 (1s) • Kruger 60 (2s) • Ross 614 (2s) • Wolf 1061 (1s) • Gliese 1 (1s) • Wolf 424 (2s) • TZ Arietis (1s) • Gliese 687 (1s) • LHS 292 (1s)‡ • Gliese 674 (1s, 1p: planet b) • GJ 1245 (3s) White Dwarf* DZ* van Maanen's Star system (1s) Brown Dwarf* M* DEN 1048-3956 (1bd) T/Y* UGPS 0722-05 (1bd)‡ [show]   15 - 20 ly A V* (White) Altair (1s) G V* (Yellow) Achird (2s) • e Eridani (1s) • Delta Pavonis (1s) K V* (Orange) Groombridge 1618 (1s) • Keid (3s) • 70 Ophiuchi (2s) • Alsafi (1s) • 33G. Librae (3s, 1bd) • 36 Ophiuchi (3s) • Gliese 783 (2s) M V* (Red dwarf) GJ 1002 (1s) • Gliese 876 (1s, 4p: planet d • planet c • planet b • planet e) • LHS 288 (1s) • Gliese 412 (2s) • AD Leonis (1s) • Gliese 832 (1s, 1p: planet b) • Gliese 682 (1s) • EV Lacertae (1s) • EI Cancri (2s) • GJ 3379 (1s) • LHS 1723 (1s) • Gliese 445 (1s) • Wolf 498 (1s) • LP 816-060 (1s) • Gliese 251 (1s) • Gliese 205 (1s) • Gliese 229 (1s, 1bd) • Gliese 693 (1s) • Gliese 752 (2s: Gliese 752 A • Gliese 752 B) • Ross 47 (1s) • Gliese 754 (1s) • BR Piscis (1s) • Gliese 588 (1s) • GJ 1005 (1s) • YZ Canis Minoris (1s) White Dwarf* DC* Stein 2051 (2s) DQ* Gliese 440 (1s)‡ • GJ 1221 (1s)‡ Brown Dwarf* M* LP 944-020 (1bd) • 2MASS 1835+3259 (1bd) L* DEN 0255-4700 (1bd) T* DEN 0817-6155 (1bd)‡ • 2MASS 0939-2448 (2bd) • 2MASS 0415-0935 (1bd) [hide]   20 - 25 ly G* (Yellow) IV* Beta Hydri (1s) V* Xi Boötis (2s) VI* Marfak-West (2s) K V* (Orange) Gliese 338 (2s)‡ • Gliese 892 (1s) • Gliese 667 (3s, 1p: planet Cb) • HR 753 (3s) • Gliese 33 (1s) • 107 Piscium (1s) • TW Piscis Austrini (1s)‡ M V* (Red dwarf) QY Aurigae (2s)‡ • HN Librae (1s)‡ • Gliese 784 (1s) • Gliese 581 (1s, 6p: planet e • planet b • planet c • planet g • planet d • planet f) • EQ Pegasi (2s) • LHS 2090 (1s) • LHS 337 (1s) • Gliese 661 (2s) • LHS 3003 (1s) • G 180-060 (1s) • Gliese 644 (5s) • GL Virginis (1s) • Gliese 625 (1s) • Gliese 408 (1s) • Gliese 829 (2s) • G 41-14 (3s) • EE Leonis (1s) • Gliese 299 (1s) • Gliese 880 (2s) • LP 771-095 (3s) • GJ 1068 (1s) • Gliese 809 (1s) • Gliese 54 (2s) • GJ 1286 (1s) • Gliese 393 (1s) • GJ 3991 (1s)‡ • GJ 4053 (1s) • Gliese 1230 (3s)‡ • GJ 2005 (1s) • GJ 4274 (1s)‡ • GJ 4248 (1s) • GJ 1224 (1s)‡ • Gliese 109 (1s)‡ • GJ 3378 (1s)‡ • Gliese 514 (1s)‡ • Gliese 480.1 (1s)‡ White Dwarf* DZ* Gliese 223.2 (1s) Brown Dwarf* L* 2MASS 1507-1627 (1bd) T* 2MASS 0937+2931 (1bd)‡ • SIMP J013656.5+093347 (1bd)‡ [show]   25 - 30 ly A V* (White) Fomalhaut (1s, 1p: planet b)‡ • Vega (1s) F V* (Yellow-white) Tabit (1s) • Batentaban Borealis (2s) • Zeta Tucanae (1s) • Gamma Leporis (2s) G* (Yellow) IV* Mu Herculis (3s) V * Alula Australis (3s, 1bd) • Chara (1s) • 61 Virginis (1s, 3p: planet b • planet c • planet d) • Chi¹ Orionis (2s) • 41 G. Arae (2s) • Beta Comae Berenices (1s)‡ • Kappa¹ Ceti (1s)‡ VI* Groombridge 1830 (1s)‡ K* (Orange) IV* Rana (1s) V* Gliese 673 (1s)‡ • Gliese 884 (1s) • p Eridani (2s) • Gliese 250 (2s) • HR 1614 (1s) • HR 7722 (1s) M V* (Red dwarf) GJ 2005 (3s)‡ • GJ 1093 (1s)‡ • Gliese 686 (1s) • Gliese 701 (1s) • Gliese 382 (1s) • SIPS 1259-4336 (1s) • GJ 3789 (1s)‡ • Gliese 793 (1s) • SSSPM J1138-7722 (1s)‡ • Gliese 831 (2s) • Gliese 257 (2s) • Gliese 623 (2s) • GJ 4063 (1s)‡ • GJ 1105 (1s) • GJ 1289 (1s) • Gliese 493.1 (1s) • Gliese 48 (1s) • Gliese 747 (2s) • Gliese 300 (1s) • Gliese 486 (1s) • GJ 1151 (1s) • LP 655-48 (1s)‡ • GJ 1227 (1s) • SCR 1138-7721 (1s) • Gl 232 (1s) • SCR 0838-5855 (1s)‡ • Gliese 438 (1s) • GJ 3146 (1s) • GJ 1154 (1s) • GJ 1057 (1s) • Gliese 618 (2s) • GJ 3076 (1s)‡ • SCR 0640-0552 (1s)‡ • Gliese 185 (2s) • Gliese 450 (1s) • GJ 3517 (1s) • Gliese 877 (1s) • Gliese 745 (2s) • Gliese 867 (2s) • GJ 3454 (2s) • Gliese 791.2 (2s) • LDS 169 (2s)‡ • Gliese 849 (1s, 1p: planet b) • GJ 1103 (2s) • GJ 1207 (1s)‡ • Gliese 465 (1s) • GJ 1277 (1s) • SCR 0630-7643 (2s) • GJ 3128 (1s) • GJ 3707 (1s)‡ • GJ 3820 (1s)‡ • GJ 4247 (1s) • Gliese 357 (1s) • Gliese 595 (1s)‡ • GJ 4360 (1s)‡ • Gliese 433 (1s, 1p: planet b) • Gliese 424 (1s) • GJ 3801 (1s)‡ • GJ 2066 (1s)‡ • GJ 3421 (2s)‡ • Gliese 317 (1s, 1p: planet b)‡ • SCR 1826-6542 (1s)‡ White Dwarf* DA* GJ 2034 (2s)‡ • GJ 1087 (1s) • Gliese 915 (1s) • Gliese 318 (1s) DC* GJ 3667 (1s) DQ* Gliese 293 (1s) • GJ 2012 (1s) DZ* Gliese 518 (1s) • GJ 1276 (1s) • Gliese 283 (2s) Brown Dwarf* L* SDSS J1416+13 (2bd)‡ • 2MASS 0036+1821 (1bd) T* 2MASS 0727+1710 (1bd)‡ *System's primary member stellar class. ‡Distance error margin extends out of declared distance interval. Components: s - star, bd - brown dwarf, p - planet

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Coordinates: 15^h 19^m 27^s, −07° 43′ 19″

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Categories: Extrasolar planets | Libra constellation | Terrestrial planets | Exoplanets discovered in 2010 | Exoplanets detected by radial velocity | Super-Earths | Gliese 581

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Press Release 10-172 - Video
Steven Vogt and Paul Butler lead a team that discovered the first potentially habitable exoplanet.

Steven Vogt of UC Santa Cruz and UC Observatories and Paul Butler of the Carnegie Institution of Washington join NSF's Lisa-Joy Zgorski to announce the discovery of the first exoplanet that has the potential to support life. Credit: National Science Foundation Back to article

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