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Gliese 581g: Difference between revisions

Coordinates: Sky map 15h 19m 27s, −07° 43′ 19″
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== Habitability ==
== Habitability ==
Gliese 581 g is expected to be [[tidally locked]] to its star,{{why}} just as our moon is to the Earth; the length of Gliese 581 g's [[sidereal day]] would then precisely match the length of its year.<ref name = "Vogt"/><ref> {{Cite web|url=http://news.sciencemag.org/sciencenow/2010/09/astronomers-find-most-earth-like.html|title=Astronomers Find Most Earth-like Planet to Date|publisher=[[Science (journal)|Science]], USA|date=September 29, 2010|accessdate=September 30, 2010}}</ref> With one side of the planet always facing the star, continuous Earth-like temperatures are imaginable in the area between the bright and the dark side. 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. Researchers have estimated that the surface temperature of the planet averages between −31 to −12 degrees Celsius (−24 and 10 degrees Fahrenheit), ranging from blazing hot in the light side to freezing cold in the dark side.<ref name="Stephens">{{cite web |last=Stephens |first=Tim |date=2010-09-29 |url=http://news.ucsc.edu/2010/09/planet.html |title=Newly discovered planet may be first truly habitable exoplanet |work=University News & Events |publisher=[[University of California, Santa Cruz]]}}</ref>
Due to the planet's closeness to its parent star it is expected to be [[tidally locked]] to Gliese 581, just as our moon is to the Earth; the length of Gliese 581 g's [[sidereal day]] would then precisely match the length of its year.<ref name = "Vogt"/><ref> {{Cite web|url=http://news.sciencemag.org/sciencenow/2010/09/astronomers-find-most-earth-like.html|title=Astronomers Find Most Earth-like Planet to Date|publisher=[[Science (journal)|Science]], USA|date=September 29, 2010|accessdate=September 30, 2010}}</ref> With one side of the planet always facing the star, continuous Earth-like temperatures are imaginable in the area between the bright and the dark side. 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. Researchers have estimated that the surface temperature of the planet averages between −31 to −12 degrees Celsius (−24 and 10 degrees Fahrenheit), ranging from blazing hot in the light side to freezing cold in the dark side.<ref name="Stephens">{{cite web |last=Stephens |first=Tim |date=2010-09-29 |url=http://news.ucsc.edu/2010/09/planet.html |title=Newly discovered planet may be first truly habitable exoplanet |work=University News & Events |publisher=[[University of California, Santa Cruz]]}}</ref>
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."<ref>NSF. [http://www.nsf.gov/news/news_videos.jsp?cntn_id=117765&media_id=68454&org=NSF Press Release 10-172 - Video]. Event occurs at 41:25-42:31. See {{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |date=2010-09-29 |url=http://www.nytimes.com/2010/09/30/science/space/30planet.html?_r=1 |title=New Planet May Be Able to Nurture Organisms |publisher=''[[The New York Times]]''|accessdate=September 30, 2010}}</ref>
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."<ref>NSF. [http://www.nsf.gov/news/news_videos.jsp?cntn_id=117765&media_id=68454&org=NSF Press Release 10-172 - Video]. Event occurs at 41:25-42:31. See {{cite news |last=Overbye |first=Dennis |authorlink=Dennis Overbye |date=2010-09-29 |url=http://www.nytimes.com/2010/09/30/science/space/30planet.html?_r=1 |title=New Planet May Be Able to Nurture Organisms |publisher=''[[The New York Times]]''|accessdate=September 30, 2010}}</ref>

Revision as of 16:58, 30 September 2010

Template:Planetbox begin Template:Planetbox image Template:Planetbox star Template:Planetbox orbit Template:Planetbox character Template:Planetbox discovery Template:Planetbox reference Template:Planetbox end Gliese 581 g (Template:Pron-en) or Gl 581 g is one of at least six extrasolar planets found around Gliese 581, an M3V red dwarf star approximately 20.5 light-years away from Earth[1] in the constellation of Libra.

The planet lies near the middle of the "Goldilocks", or habitable zone of its parent star, and the presence of liquid water is considered a strong possibility.[2] The discovery of Gliese 581 g was announced in late September 2010,[3] 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.[4]

Discovery

The orbits of the Gliese 581 planetary system. In the picture, Gliese 581 g is plotted with a circular orbit between c and d.

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.[3][5] The planet is believed to have a mass of three to four times that of the Earth and an orbital period of just under 37 days, orbiting at a distance of 0.146 AU from its parent star.

The Steven Vogt et al team has unofficially adopted the name "Zarmina" for the planet, after Steven Vogt's wife.[6]

The discovery of a habitable planet so early in the search for exoplanets, after scientists had monitored only a relatively small number of stars for this purpose, could mean that such planets are more widely distributed than had been believed. Vogt now believes that the ratio of systems with habitable planets is 10%—20%.[7]

Habitability

Due to the planet's closeness to its parent star it is expected to be tidally locked to Gliese 581, just as our moon is to the Earth; the length of Gliese 581 g's sidereal day would then precisely match the length of its year.[3][8] With one side of the planet always facing the star, continuous Earth-like temperatures are imaginable in the area between the bright and the dark side. 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. Researchers have estimated that the surface temperature of the planet averages between −31 to −12 degrees Celsius (−24 and 10 degrees Fahrenheit), ranging from blazing hot in the light side to freezing cold in the dark side.[9]

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."[10]

In their paper published in the Astrophysics Journal their figures are some what less optimistic:

With this assumption, in the absence of tidal heating sources, the average surface temperatures on GJ 581g would be 236 to 258 K (-37°C to -15°C). Alternatively, if we assume that an Earth-like greenhouse effect would simply raise the equilibrium temperature by 33 K (33°C), similar to Earth’s greenhouse, the surface temperature would still be about the same, 242 to 261 K (-31°C to -12°C).

- Steven S. Vogt et al. 2010, page 31

For comparison, Martian surface temperatures vary from lows of about -87 °C during the polar winters to highs of up to -5 °C in summers.[11] The wide range in temperatures is due to the thin atmosphere which cannot store much solar heat, the low atmospheric pressure, and the low thermal inertia of Martian soil.[12] The planet is also 1.52 times as far from the sun as Earth, resulting in just 43 percent of the amount of sunlight.[13]

References

  1. ^ About 193 trillion kilometres
  2. ^ Shiga, David (2010-09-29). "Found: first rocky exoplanet that could host life". New Scientist. Retrieved September 30, 2010. {{cite news}}: Italic or bold markup not allowed in: |publisher= (help)
  3. ^ a b c Vogt, Steven S. (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. Retrieved 2010-09-29. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  4. ^ "Just-right planet that can support life detected". Reuters, USA. September 29, 2010. Retrieved September 30, 2010.
  5. ^ Alleyne, Richard (September 30, 2010). "Gliese 581g the most Earth like planet yet discovered". The Daily Telegraph. Retrieved September 30, 2010. {{cite news}}: Italic or bold markup not allowed in: |publisher= (help)
  6. ^ Borenstein, Seth (2010-09-29). "Could 'Goldilocks' planet be just right for life?". Associated Press. Retrieved September 30, 2010.
  7. ^ Berardelli, Phil (2010-09-29). "Astronomers Find Most Earth-like Planet to Date". AAAS. Retrieved September 30, 2010.
  8. ^ "Astronomers Find Most Earth-like Planet to Date". Science, USA. September 29, 2010. 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.
  10. ^ 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. Retrieved September 30, 2010. {{cite news}}: Italic or bold markup not allowed in: |publisher= (help)
  11. ^ Cite error: The named reference h was invoked but never defined (see the help page).
  12. ^ Cite error: The named reference nasa_surface was invoked but never defined (see the help page).
  13. ^ Cite error: The named reference disc920901 was invoked but never defined (see the help page).
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