# Gliese 581c

> Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Gliese_581c
> Markdown URL: https://mediated.wiki/source/Gliese_581c.md
> Source: https://en.wikipedia.org/wiki/Gliese_581c
> Source revision: 1341384046
> License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/)

Super-Earth exoplanet orbiting Gliese 581

Gliese 581c Size comparison of Gliese 581c with Earth and Neptune (based on selected hypothetical modeled compositions)[a] Discovery[1] Discovered by Stéphane Udry et al. Discovery site La Silla Observatory Discovery date 4 April 2007 24 April 2007 (announced) Detection method Radial velocity Orbital characteristics[2] Semi-major axis 0.0718+0.0008 −0.0009 AU Eccentricity 0.032+0.027 −0.021 Orbital period (sidereal) 12.9211+0.0008 −0.0007 d Inclination 47°+15° −13° Time of periastron 2454759.2 ± 0.1[3] Argument of periastron 16°+61° −89° Semi-amplitude 3.1±0.1 m/s Star Gliese 581 Physical characteristics[2] Mass 6.81+0.21 −1.16 M🜨

**Gliese 581c** [/ˈɡliːzə/](https://en.wikipedia.org/wiki/Help:IPA/English) (**Gl 581c** or **GJ 581c**) is an [exoplanet](/source/Exoplanet) orbiting within the [Gliese 581](/source/Gliese_581) system. It is the second planet discovered in the system and the third in order from the [star](/source/Star). With a mass about 6.8 times that of the [Earth](/source/Earth), it is classified as a [super-Earth](/source/Super-Earth) (a category of planets with masses greater than Earth's up to ten Earth masses).

At the time of its discovery in 2007, Gliese 581c gained interest from astronomers because it was reported to be the first potentially Earth-like planet in the [habitable zone](/source/Habitable_zone) of its star, with a temperature right for liquid water on its surface, and, by extension, potentially capable of supporting [extremophile](/source/Extremophile) forms of Earth-like life. However, further research cast doubt upon the planet's [habitability](/source/Habitability). Based on newer models of the habitable zone, the planet is likely too hot to be potentially habitable.[4][3]

In astronomical terms, the Gliese 581 system is relatively close to Earth, at 20.55 [light-years](/source/Light-year) (194 trillion kilometres; 121 trillion miles) in the direction of the [constellation](/source/Constellation) of [Libra](/source/Libra_(constellation)). This distance, along with the [declination](/source/Declination) and [right ascension](/source/Right_ascension) coordinates, give its exact location in the [Milky Way](/source/Milky_Way).

## Discovery

The team released a paper of their findings dated 27 April 2007, published in the July 2007 journal *[Astronomy & Astrophysics](/source/Astronomy_%26_Astrophysics)*.[1] At the time of discovery, it was reported to be the first potentially Earth-like planet in the [habitable zone](/source/Habitable_zone) of its star[5][6] and the smallest-known [exoplanet](/source/Exoplanet) around a [main-sequence](/source/Main_sequence) star, but on 21 April 2009, another planet orbiting Gliese 581, [Gliese 581e](/source/Gliese_581e), with an approximate mass of 1.9 [Earth masses](/source/Earth_mass), was announced. In the paper, they also announced the discovery of another planet in the system, [Gliese 581d](/source/Gliese_581d), with a minimum mass of 7.7 Earth masses and a [semi-major axis](/source/Semi-major_axis) of 0.25 [astronomical units](/source/Astronomical_unit).[7][3]

## Physical characteristics

### Mass

The existence of Gliese 581c and its mass have been measured by the [radial velocity method](/source/Methods_of_detecting_exoplanets#Radial_velocity) of detecting [exoplanets](/source/Exoplanet). The mass of a planet is calculated by the small periodic movements around a common centre of mass between the host star Gliese 581 and its planets. When all planets are fitted with a [Keplerian](/source/Kepler's_laws_of_planetary_motion) solution, the [minimum mass](/source/Minimum_mass) of the planet is determined to be 5.5 Earth masses.[3] The radial velocity method cannot by itself determine the true mass, but it cannot be very much larger than this or the system would be dynamically unstable.[1] Dynamical simulations of the Gliese 581 system which assume the orbits of the planets are [coplanar](/source/Coplanar) indicate that the planets cannot exceed approximately 1.6 to 2 times their minimum masses or the planetary system would be unstable (this is primarily due to the interaction between planets e and b). For Gliese 581c, the upper bound is 10.4 Earth masses.[7]

A 2024 study determined the inclination of the planet, allowing its true mass to be determined, which is about 30% greater than the minimum mass at about 6.8 [Earth masses](/source/Earth_mass).[2]

### Radius

Since Gliese 581c has not been detected in transit, there are no measurements of its radius. Furthermore, the [radial velocity method](/source/Radial_velocity_method) used to detect it only puts a lower limit on the planet's mass, which means theoretical models of planetary radius and structure can only be of limited use. However, assuming a random orientation of the planet's orbit, the true mass is likely to be close to the measured minimum mass.

Assuming that the true mass is the minimum mass, the radius may be calculated using various models. For example, if Gliese 581c is a [rocky](/source/Rock_(geology)) planet with a large iron core, it should have a radius approximately 50% larger than that of Earth, according to Udry's team.[1][8] [Gravity](/source/Gravity) on such a planet's surface would be approximately 2.24 times as strong as on Earth. However, if Gliese 581c is an [icy](/source/Ice) and/or [watery](/source/Water) planet, its radius would be less than 2 times that of Earth, even with a very large outer [hydrosphere](/source/Hydrosphere), according to density models compiled by Diana Valencia and her team for [Gliese 876 d](/source/Gliese_876_d).[9] Gravity on the surface of such an icy and/or watery planet would be at least 1.25 times as strong as on Earth. They claim the real value of the radius may be anything between the two extremes calculated by density models outlined above.[10]

Other scientists' views differ. [Sara Seager](/source/Sara_Seager) at MIT has speculated that Gliese 581c and other five-Earth-mass planets could be:[11]

- "rock giants" mostly of [silicate](/source/Silicate);

- "cannonball" planets of solid [iron](/source/Iron);

- "gas dwarfs" mostly of [helium](/source/Helium) and [hydrogen](/source/Hydrogen);

- carbon-rich "[diamond](/source/Diamond) worlds";

- purely hot "[ice VII](/source/Ice_VII) worlds";

- purely "[carbon monoxide](/source/Carbon_monoxide) worlds".

If the planet transits the star as seen from the direction of the Earth, the radius should be measurable, albeit with some uncertainty. Unfortunately, measurements made with the Canadian-built [MOST](/source/MOST_(spacecraft)) space telescope indicate that transits do not occur.[12]

The new research suggests that the rocky centres of super-Earths are unlikely to evolve into terrestrial rocky planets like the inner planets of the Solar System because they appear to hold onto their large atmospheres. Rather than evolving to a planet composed mainly of rock with a thin atmosphere, the small rocky core remains engulfed by its large hydrogen-rich envelope.[13][14]

### Orbit

The orbits of the [Gliese 581](/source/Gliese_581) system, as per the 2009 four-planet model. In the picture, Gliese 581c is the third planet from the star.

Gliese 581c has an [orbital period](/source/Orbital_period) ("year") of 13 Earth days[15] and its orbital radius is only about 7% that of the Earth, about 11 million km,[16] while the Earth is 150 million km from the [Sun](/source/Sun).[17] Since the host star is smaller and colder than the Sun—and thus less luminous—this distance places the planet on the "warm" edge of the habitable zone around the star according to Udry's team.[1][8] Note that in astrophysics, the "habitable zone" is defined as the range of distances from the star at which a planet could support liquid water on its surface: it should not be taken to mean that the planet's environment would be suitable for humans, a situation which requires a more restrictive range of parameters. In any case, based on newer models of the habitable zone, the planet is likely too hot to be potentially habitable.[4][3]

A typical radius for an M0 star of Gliese 581's age and [metallicity](/source/Metallicity) is 0.00128 AU,[18] against the Sun's 0.00465 AU. This proximity means that the primary star should appear 3.75 times wider and 14 times larger in area for an observer on the planet's surface looking at the sky than the Sun appears to be from Earth's surface.

### Tidal lock

Because of its small separation from Gliese 581, the planet has been generally considered to always have one [hemisphere](/source/Sphere) facing the star (only day), and the other always facing away (only night), or in other words being [tidally locked](/source/Tidally_locked).[19][20] The most recent orbital fit to the system, taking stellar activity into account indicates a nearly circular orbit,[2] but older fits used an eccentricity between 0.10 and 0.22. If the orbit of the planet were eccentric, it would undergo violent tidal flexing.[21] Because tidal forces are stronger when the planet is close to the star, eccentric planets are expected to have a rotation period that is shorter than its orbital period, also called pseudo-synchronization.[22] An example of this effect is seen in [Mercury](/source/Mercury_(planet)), which is tidally locked in a 3:2 resonance, completing three rotations every two orbits. In any case, even in the case of 1:1 tidal lock, the planet would undergo [libration](/source/Libration) and the terminator would be alternatively lit and darkened during libration.[23]

Models of the evolution of the planet's orbit over time suggest that [heating](/source/Tidal_heating) resulting from this tidal locking may play a major role in the planet's geology. Models proposed by scientists predict that tidal heating could yield a surface heat flux about three times greater than that of [Jupiter](/source/Jupiter)'s moon [Io](/source/Io_(moon)), which could result in major geological activity such as volcanoes and plate tectonics.[24]

## Habitability and climate

The study of Gliese 581c by the von Bloh et al. team is quoted as concluding "The super-Earth Gl 581c is clearly outside the habitable zone, since it is too close to the star."[4] The study by Selsis et al. states that "a planet in the habitable zone is not necessarily habitable" itself, and this planet "is outside what can be considered the conservative habitable zone" of the parent star, and further that if there was any water there then it was lost when the red dwarf was a strong X-ray and EUV emitter, it could have surface temperatures ranging from 700 to 1,000 [K](/source/Kelvin) (427 to 727 [°C](/source/Celsius)), like [Venus](/source/Venus) today.[25] Temperature speculations by other scientists were based on the temperature of (and heat from) the parent star [Gliese 581](/source/Gliese_581) and have been calculated without factoring in the margin of error (96 °C/K) for the star's temperature of 3,432 K to 3,528 K, which leads to a large [irradiance](/source/Irradiance) range for the planet, even before eccentricity is considered.[26]

### Effective temperatures

Using the measured stellar luminosity of Gliese 581 of 0.013 times that of the Sun, it is possible to calculate Gliese 581c's [effective temperature](/source/Effective_temperature), a.k.a. [black body](/source/Black_body) temperature, which probably differs from its [surface temperature](/source/Planetary_equilibrium_temperature).[*[citation needed](https://en.wikipedia.org/wiki/Wikipedia:Citation_needed)*] According to Udry's team, the effective temperature for Gliese 581c, assuming an [albedo](/source/Albedo) (reflectivity) such as that of Venus (0.64), would be −3 °C (27 [°F](/source/Fahrenheit)), and assuming an Earth-like albedo (0.296), it would be 40 °C (104 °F),[1][15] a range of temperatures that overlap with the [range at which water would be liquid at a pressure of 1 atmosphere](/source/Orders_of_magnitude_(temperature)#liquid_water). However, the effective temperature and actual surface temperature can be very different due to the greenhouse properties of the planetary atmosphere. For example, Venus has an effective temperature of −41 °C (−42 °F), but a surface temperature of 464 °C (867 °F) (mainly due to a 96.5% [carbon dioxide atmosphere](/source/Atmosphere_of_Venus)), a difference of about 505 °C (910 °F).[27]

Studies of habitability (i.e. liquid water for [extremophile](/source/Extremophile) forms of life)[28] conclude that Gliese 581c is likely to suffer from a [runaway greenhouse effect](/source/Runaway_greenhouse_effect) similar to that found on [Venus](/source/Atmosphere_of_Venus) and, as such, is highly unlikely to be habitable. Nevertheless, this runaway greenhouse effect could be prevented by the presence of sufficient reflective cloud cover on the planet's day side.[29] Alternatively, if the surface were covered in ice, it would have a high [albedo](/source/Albedo) (reflectivity), and thus could reflect enough of the incident sunlight back into space to render the planet too cold for habitability, although this situation is expected to be very unstable except for very high albedos greater than about 0.95 (i.e. ice): release of [carbon dioxide](/source/Carbon_dioxide) by volcanic activity or of water vapor due to heating at the substellar point would trigger a runaway greenhouse effect.[30]

### Liquid water

Gliese 581c is likely to lie outside the [habitable zone](/source/Habitable_zone).[4][31] No direct evidence has been found for [water](/source/Water) to be present, and it is probably not present in the liquid state. Techniques like the one used to measure the extrasolar planet [HD 209458 b](/source/HD_209458_b) may in the future be used to determine the presence of water in the form of vapor in the planet's [atmosphere](/source/Atmosphere), but only in the rare case of a planet with an orbit aligned so as to [transit](/source/Astronomical_transit) its star, which Gliese 581c is not known to do.[12]

### Tidally locked models

Theoretical models predict that volatile [compounds](/source/Chemical_compound) such as [water](/source/Water_(molecule)) and [carbon dioxide](/source/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](/source/Ice_cap). Over time, the entire atmosphere might freeze into ice caps on the night side of the planet. However, it remains unknown if water and/or carbon dioxide are even present on the surface of Gliese 581c. Alternatively, an atmosphere large enough to be stable would circulate the heat more evenly, allowing for a wider habitable area on the surface.[32] For example, although [Venus](/source/Venus) has a small axial inclination, very little sunlight reaches the surface at the poles. A slow rotation rate approximately 117 times slower than Earth's produces prolonged days and nights. Despite the uneven distribution of sunlight cast on Venus at any given time, polar areas and the night side of Venus are kept almost as hot as on the day side by globally circulating winds.[33]

## A Message from Earth

A Message from Earth (AMFE) is a high-powered digital radio signal that was sent on 9 October 2008 towards Gliese 581c. The signal is a digital [time capsule](/source/Time_capsule) containing 501 messages that were selected through a competition on the [social networking site](/source/Social_networking_site) [Bebo](/source/Bebo). The message was sent using the [RT-70](/source/RT-70) [radar telescope](/source/Radar_telescope) of [Ukraine](/source/Ukraine)'s [State Space Agency](/source/State_Space_Agency_of_Ukraine). The signal will reach the planet Gliese 581c in early 2029.[34] More than half a million people including celebrities and politicians participated in the AMFE project, which was the world's first digital time capsule where the content was selected by the public.[35][36]

## In popular culture

Estonian singer [Laura Põldvere](/source/Laura_P%C3%B5ldvere) sings poetically about the "beautiful far-away planet" in her song *581c*.[37]

## See also

- [Circumstellar habitable zone](/source/Circumstellar_habitable_zone) (Goldilocks phenomenon)

- [CoRoT-7b](/source/CoRoT-7b)

- [Interstellar travel](/source/Interstellar_travel)

- [Planetary habitability](/source/Planetary_habitability)

## Notes

1. **[^](#cite_ref-1)** The estimated range of sizes in this image from 2009 is based on the planet's [minimum mass](/source/Minimum_mass). Since the true mass is now known to be somewhat greater, the sizes are likely underestimated, especially if the planet has a hydrogen atmosphere.

## References

1. ^ [***a***](#cite_ref-udry_2-0) [***b***](#cite_ref-udry_2-1) [***c***](#cite_ref-udry_2-2) [***d***](#cite_ref-udry_2-3) [***e***](#cite_ref-udry_2-4) [***f***](#cite_ref-udry_2-5) Udry, Stéphane; Bonfils, Xavier; Delfosse, Xavier; Forveille, Thierry; Mayor, Michel; Perrier, Christian; Bouchy, François; Lovis, Christophe; Pepe, Francesco; Queloz, Didier; Bertaux, Jean-Loup (2007). ["The HARPS search for southern extra-solar planets XI. Super-Earths (5 and 8 M🜨) in a 3-planet system"](https://web.archive.org/web/20101008120426/http://exoplanet.eu/papers/udry_terre_HARPS-1.pdf) (PDF). *Astronomy & Astrophysics*. **469** (3): L43–L47. [arXiv](/source/ArXiv_(identifier)):[0704.3841](https://arxiv.org/abs/0704.3841). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...469L..43U](https://ui.adsabs.harvard.edu/abs/2007A&A...469L..43U). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20077612](https://doi.org/10.1051%2F0004-6361%3A20077612). [S2CID](/source/S2CID_(identifier)) [119144195](https://api.semanticscholar.org/CorpusID:119144195). Archived from [the original](http://exoplanet.eu/papers/udry_terre_HARPS-1.pdf) (PDF) on 8 October 2010.

1. ^ [***a***](#cite_ref-vonStauffenberg2024_3-0) [***b***](#cite_ref-vonStauffenberg2024_3-1) [***c***](#cite_ref-vonStauffenberg2024_3-2) [***d***](#cite_ref-vonStauffenberg2024_3-3) von Stauffenberg, A.; Trifonov, T.; Quirrenbach, A.; et al. (5 June 2024). "The CARMENES search for exoplanets around M dwarfs. Revisiting the GJ 581 multi-planetary system with new Doppler measurements from CARMENES, HARPS, and HIRES". *Astronomy & Astrophysics*. **688**. [arXiv](/source/ArXiv_(identifier)):[2407.11520](https://arxiv.org/abs/2407.11520). [Bibcode](/source/Bibcode_(identifier)):[2024A&A...688A.112V](https://ui.adsabs.harvard.edu/abs/2024A&A...688A.112V). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/202449375](https://doi.org/10.1051%2F0004-6361%2F202449375). [ISSN](/source/ISSN_(identifier)) [0004-6361](https://search.worldcat.org/issn/0004-6361).

1. ^ [***a***](#cite_ref-robertson2014_4-0) [***b***](#cite_ref-robertson2014_4-1) [***c***](#cite_ref-robertson2014_4-2) [***d***](#cite_ref-robertson2014_4-3) [***e***](#cite_ref-robertson2014_4-4) Robertson, Paul; [Mahadevan, Suvrath](/source/Suvrath_Mahadevan); Endl, Michael; Roy, Arpita (3 July 2014). "Stellar activity masquerading as planets in the habitable zone of the M dwarf Gliese 581". *[Science](/source/Science_(journal))*. **345** (6195): 440–444. [arXiv](/source/ArXiv_(identifier)):[1407.1049](https://arxiv.org/abs/1407.1049). [Bibcode](/source/Bibcode_(identifier)):[2014Sci...345..440R](https://ui.adsabs.harvard.edu/abs/2014Sci...345..440R). [doi](/source/Doi_(identifier)):[10.1126/science.1253253](https://doi.org/10.1126%2Fscience.1253253). [PMID](/source/PMID_(identifier)) [24993348](https://pubmed.ncbi.nlm.nih.gov/24993348). [S2CID](/source/S2CID_(identifier)) [206556796](https://api.semanticscholar.org/CorpusID:206556796).

1. ^ [***a***](#cite_ref-blo07_5-0) [***b***](#cite_ref-blo07_5-1) [***c***](#cite_ref-blo07_5-2) [***d***](#cite_ref-blo07_5-3) von Bloh; et al. (2007). "The Habitability of Super-Earths in Gliese 581". *[Astronomy and Astrophysics](/source/Astronomy_and_Astrophysics)*. **476** (3): 1365–1371. [arXiv](/source/ArXiv_(identifier)):[0705.3758](https://arxiv.org/abs/0705.3758). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...476.1365V](https://ui.adsabs.harvard.edu/abs/2007A&A...476.1365V). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20077939](https://doi.org/10.1051%2F0004-6361%3A20077939). [S2CID](/source/S2CID_(identifier)) [14475537](https://api.semanticscholar.org/CorpusID:14475537).

1. **[^](#cite_ref-space.com_6-0)** Than, Ker (24 April 2007). ["Major Discovery: New Planet Could Harbor Water and Life"](http://www.space.com/scienceastronomy/070424_hab_exoplanet.html). space.com. [Archived](https://web.archive.org/web/20101224061707/http://www.space.com/scienceastronomy/070424_hab_exoplanet.html) from the original on 24 December 2010. Retrieved 29 April 2007.

1. **[^](#cite_ref-7)** Than, Ker (24 February 2007). ["Planet Hunters Edge Closer to Their Holy Grail"](http://www.space.com/scienceastronomy/070424_exoplanet_side.html). space.com. [Archived](https://web.archive.org/web/20101213185629/http://www.space.com/scienceastronomy/070424_exoplanet_side.html) from the original on 13 December 2010. Retrieved 29 April 2007.

1. ^ [***a***](#cite_ref-Mayor2009_8-0) [***b***](#cite_ref-Mayor2009_8-1) Mayor, Michel; Bonfils, Xavier; Forveille, Thierry; et al. (2009). ["The HARPS search for southern extra-solar planets, XVIII. An Earth-mass planet in the GJ 581 planetary system"](https://web.archive.org/web/20090521052641/http://obswww.unige.ch/~udry/Gl581_preprint.pdf) (PDF). *[Astronomy and Astrophysics](/source/Astronomy_and_Astrophysics)*. **507** (1): 487–494. [arXiv](/source/ArXiv_(identifier)):[0906.2780](https://arxiv.org/abs/0906.2780). [Bibcode](/source/Bibcode_(identifier)):[2009A&A...507..487M](https://ui.adsabs.harvard.edu/abs/2009A&A...507..487M). [doi](/source/Doi_(identifier)):[10.1051/0004-6361/200912172](https://doi.org/10.1051%2F0004-6361%2F200912172). [S2CID](/source/S2CID_(identifier)) [2983930](https://api.semanticscholar.org/CorpusID:2983930). Archived from [the original](http://obswww.unige.ch/~udry/Gl581_preprint.pdf) (PDF) on 21 May 2009.

1. ^ [***a***](#cite_ref-ESOAstronomy_9-0) [***b***](#cite_ref-ESOAstronomy_9-1) ["Astronomers Find First Earth-like Planet in Habitable Zone"](https://web.archive.org/web/20080828055304/http://eso.org/outreach/press-rel/pr-2007/pr-22-07.html). ESO. Archived from [the original](http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html) on 28 August 2008. Retrieved 10 May 2007.

1. **[^](#cite_ref-10)** Valencia; Sasselov, Dimitar D.; O'Connell, Richard J. (2007). "Radius and Structure Models of the First Super-Earth Planet". *[The Astrophysical Journal](/source/The_Astrophysical_Journal)*. **656** (1): 545–551. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0610122](https://arxiv.org/abs/astro-ph/0610122). [Bibcode](/source/Bibcode_(identifier)):[2007ApJ...656..545V](https://ui.adsabs.harvard.edu/abs/2007ApJ...656..545V). [doi](/source/Doi_(identifier)):[10.1086/509800](https://doi.org/10.1086%2F509800). [S2CID](/source/S2CID_(identifier)) [17656317](https://api.semanticscholar.org/CorpusID:17656317).

1. **[^](#cite_ref-11)** Valencia, D.; Sasselov, Dimitar D.; O’Connell, Richard J. (2007). "Detailed Models of Super-Earths: How Well Can We Infer Bulk Properties?". *[The Astrophysical Journal](/source/The_Astrophysical_Journal)*. **665** (2): 1413–1420. [arXiv](/source/ArXiv_(identifier)):[0704.3454](https://arxiv.org/abs/0704.3454). [Bibcode](/source/Bibcode_(identifier)):[2007ApJ...665.1413V](https://ui.adsabs.harvard.edu/abs/2007ApJ...665.1413V). [doi](/source/Doi_(identifier)):[10.1086/519554](https://doi.org/10.1086%2F519554). [S2CID](/source/S2CID_(identifier)) [15605519](https://api.semanticscholar.org/CorpusID:15605519).

1. **[^](#cite_ref-12)** Seager (2008). ["Alien Earths from A to Z"](https://web.archive.org/web/20090815031622/http://pqasb.pqarchiver.com/skyandtelescope/access/1478225761.html?dids=1478225761&FMT=ABS&FMTS=ABS&date=Jan+2008&author=Sara+Seager&desc=Alien+Earths+from+A+to+Z). *[Sky & Telescope](/source/Sky_%26_Telescope)*. ISSN. 0037–6604 (January): 22–25. [Bibcode](/source/Bibcode_(identifier)):[2008S&T...115a..22S](https://ui.adsabs.harvard.edu/abs/2008S&T...115a..22S). Archived from [the original](https://pqasb.pqarchiver.com/skyandtelescope/access/1478225761.html?dids=1478225761&FMT=ABS&FMTS=ABS&date=Jan+2008&author=Sara+Seager&desc=Alien+Earths+from+A+to+Z) on 15 August 2009. Retrieved 6 July 2017.

1. ^ [***a***](#cite_ref-Spaceref.com_13-0) [***b***](#cite_ref-Spaceref.com_13-1) ["Boring Star May Mean Livelier Planet"](http://www.spaceref.com/news/viewpr.html?pid=22805). Spaceref.com. 10 June 2007. Retrieved 15 September 2008.{{[cite web](https://en.wikipedia.org/wiki/Template:Cite_web)}}: CS1 maint: deprecated archival service ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_deprecated_archival_service))

1. **[^](#cite_ref-14)** Black, Charles. ["Super-Earths are more like mini-Neptunes"](http://sen.com/news/super-earths-could-be-more-like-mini-neptunes.html). [Archived](https://web.archive.org/web/20130314060226/http://www.sen.com/news/super-earths-could-be-more-like-mini-neptunes.html) from the original on 14 March 2013. Retrieved 14 March 2013.

1. **[^](#cite_ref-15)** Lammer, Helmut (2013). ["Probing the blow-off criteria of hydrogen-rich 'super-Earths'"](https://doi.org/10.1093%2Fmnras%2Fsts705). *Monthly Notices of the Royal Astronomical Society*. **430** (2). Royal Astronomical Society: 1247–1256. [arXiv](/source/ArXiv_(identifier)):[1210.0793](https://arxiv.org/abs/1210.0793). [Bibcode](/source/Bibcode_(identifier)):[2013MNRAS.430.1247L](https://ui.adsabs.harvard.edu/abs/2013MNRAS.430.1247L). [doi](/source/Doi_(identifier)):[10.1093/mnras/sts705](https://doi.org/10.1093%2Fmnras%2Fsts705). [S2CID](/source/S2CID_(identifier)) [55890198](https://api.semanticscholar.org/CorpusID:55890198).

1. ^ [***a***](#cite_ref-BBC1_16-0) [***b***](#cite_ref-BBC1_16-1) ["New 'super-Earth' found in space"](https://news.bbc.co.uk/2/hi/science/nature/6589157.stm). *BBC News*. 25 April 2007. [Archived](https://web.archive.org/web/20121110172300/http://news.bbc.co.uk/2/hi/science/nature/6589157.stm) from the original on 10 November 2012. Retrieved 25 April 2007.

1. **[^](#cite_ref-17)** Overbye, Dennis (25 April 2007). ["20 light years away, the most Earthlike planet yet"](http://www.iht.com/articles/2007/04/25/news/planet.php). International Herald Tribune. [Archived](https://web.archive.org/web/20070427004440/http://www.iht.com/articles/2007/04/25/news/planet.php) from the original on 27 April 2007. Retrieved 10 May 2007.

1. **[^](#cite_ref-18)** ["Earth Fact Sheet"](https://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html). NASA. [Archived](https://web.archive.org/web/20130508021904/http://nssdc.gsfc.nasa.gov/planetary/factsheet/earthfact.html) from the original on 8 May 2013. Retrieved 21 December 2015.

1. **[^](#cite_ref-19)** Girardi L.; Bressan A.; Bertelli G.; Chiosi C. (2000). "Evolutionary tracks and isochrones for low- and intermediate-mass stars: From 0.15 to 7 M☉, and from Z=0.0004 to 0.03". *Astron. Astrophys. Suppl. Ser*. **141** (3): 371–383. [arXiv](/source/ArXiv_(identifier)):[astro-ph/9910164](https://arxiv.org/abs/astro-ph/9910164). [Bibcode](/source/Bibcode_(identifier)):[2000A&AS..141..371G](https://ui.adsabs.harvard.edu/abs/2000A&AS..141..371G). [doi](/source/Doi_(identifier)):[10.1051/aas:2000126](https://doi.org/10.1051%2Faas%3A2000126). [S2CID](/source/S2CID_(identifier)) [14566232](https://api.semanticscholar.org/CorpusID:14566232).

1. **[^](#cite_ref-20)** Vergano, Dan (25 April 2007). ["Out of our world: Earthlike planet"](https://www.usatoday.com/printedition/news/20070425/1a_bottomstrip25_dom.art.htm). USA Today. [Archived](https://web.archive.org/web/20110523021921/http://www.usatoday.com/printedition/news/20070425/1a_bottomstrip25_dom.art.htm) from the original on 23 May 2011. Retrieved 10 May 2007.

1. **[^](#cite_ref-21)** [Selsis 2.4.1](#Selsis) "becomes tidally locked in less than 1 Gyr. "

1. **[^](#cite_ref-22)** Beust, H.; et al. (2008). "Dynamical evolution of the Gliese 581 planetary system". *[Astronomy and Astrophysics](/source/Astronomy_and_Astrophysics)*. **479** (1): 277–282. [arXiv](/source/ArXiv_(identifier)):[0712.1907](https://arxiv.org/abs/0712.1907). [Bibcode](/source/Bibcode_(identifier)):[2008A&A...479..277B](https://ui.adsabs.harvard.edu/abs/2008A&A...479..277B). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078794](https://doi.org/10.1051%2F0004-6361%3A20078794). [S2CID](/source/S2CID_(identifier)) [119152085](https://api.semanticscholar.org/CorpusID:119152085).

1. **[^](#cite_ref-23)** Hut, P. (1981). "Tidal Evolution in Close Binary Systems". *Astronomy and Astrophysics*. **99** (1): 126–140. [Bibcode](/source/Bibcode_(identifier)):[1981A&A....99..126H](https://ui.adsabs.harvard.edu/abs/1981A&A....99..126H).

1. **[^](#cite_ref-24)** Perlman, David (24 April 2007). ["New planet found: It might hold life"](https://web.archive.org/web/20070427094504/http://sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/24/BAG33PE14U26.DTL). *[San Francisco Chronicle](/source/San_Francisco_Chronicle)*. Archived from [the original](http://www.sfgate.com/cgi-bin/article.cgi?f=/c/a/2007/04/24/BAG33PE14U26.DTL) on 27 April 2007. Retrieved 24 April 2007.

1. **[^](#cite_ref-25)** Jackson, Brian; Richard Greenberg; Rory Barnes (2008). "Tidal Heating of Extra-Solar Planets". *Astrophysical Journal*. **681** (2): 1631–1638. [arXiv](/source/ArXiv_(identifier)):[0803.0026](https://arxiv.org/abs/0803.0026). [Bibcode](/source/Bibcode_(identifier)):[2008ApJ...681.1631J](https://ui.adsabs.harvard.edu/abs/2008ApJ...681.1631J). [doi](/source/Doi_(identifier)):[10.1086/587641](https://doi.org/10.1086%2F587641). [S2CID](/source/S2CID_(identifier)) [42315630](https://api.semanticscholar.org/CorpusID:42315630).

1. **[^](#cite_ref-26)** Selsis, Franck; Kasting, James F.; Levrard, Benjamin; Paillet, Jimmy; Ribas, Ignasi; Delfosse, Xavier (2007). ["Habitable planets around the star Gl 581?"](https://hal.archives-ouvertes.fr/hal-00182743). *[Astronomy and Astrophysics](/source/Astronomy_and_Astrophysics)*. **476** (3): 1373–1387. [arXiv](/source/ArXiv_(identifier)):[0710.5294](https://arxiv.org/abs/0710.5294). [Bibcode](/source/Bibcode_(identifier)):[2007A&A...476.1373S](https://ui.adsabs.harvard.edu/abs/2007A&A...476.1373S). [doi](/source/Doi_(identifier)):[10.1051/0004-6361:20078091](https://doi.org/10.1051%2F0004-6361%3A20078091). [S2CID](/source/S2CID_(identifier)) [11492499](https://api.semanticscholar.org/CorpusID:11492499). [Archived](https://web.archive.org/web/20181104170049/https://hal.archives-ouvertes.fr/hal-00182743) from the original on 4 November 2018. Retrieved 4 November 2018.

1. **[^](#cite_ref-27)** 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. [arXiv](/source/ArXiv_(identifier)):[astro-ph/0611060](https://arxiv.org/abs/astro-ph/0611060). [Bibcode](/source/Bibcode_(identifier)):[2006ApJ...653L..65B](https://ui.adsabs.harvard.edu/abs/2006ApJ...653L..65B). [doi](/source/Doi_(identifier)):[10.1086/510527](https://doi.org/10.1086%2F510527). [S2CID](/source/S2CID_(identifier)) [16002711](https://api.semanticscholar.org/CorpusID:16002711).

1. **[^](#cite_ref-28)** ["Venus Fact Sheet"](https://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html). NASA. [Archived](https://web.archive.org/web/20160308174416/http://nssdc.gsfc.nasa.gov/planetary/factsheet/venusfact.html) from the original on 8 March 2016. Retrieved 20 September 2008.

1. **[^](#cite_ref-29)** [Selsis 5.](#Selsis) "Gl 581c is very unlikely to be habitable"

1. **[^](#cite_ref-30)** [Selsis 3.1](#Selsis) "would be habitable only if clouds with the highest reflectivity covered most of the daytime hemisphere. "

1. **[^](#cite_ref-31)** [Selsis 3.1.2](#Selsis)

1. **[^](#cite_ref-32)** [Selsis](#Selsis) Abstract, 3. Figure 4.

1. **[^](#cite_ref-33)** Alpert, Mark (7 November 2005). ["Red Star Rising"](https://web.archive.org/web/20071012142513/http://www.sciam.com/article.cfm?chanID=sa004&articleID=000CC344-B043-1353-AF3383414B7FFE9F). *Scientific American*. **293** (5): 28. [Bibcode](/source/Bibcode_(identifier)):[2005SciAm.293e..28A](https://ui.adsabs.harvard.edu/abs/2005SciAm.293e..28A). [doi](/source/Doi_(identifier)):[10.1038/scientificamerican1105-28](https://doi.org/10.1038%2Fscientificamerican1105-28). [PMID](/source/PMID_(identifier)) [16318021](https://pubmed.ncbi.nlm.nih.gov/16318021). Archived from [the original](http://www.sciam.com/article.cfm?chanID=sa004&articleID=000CC344-B043-1353-AF3383414B7FFE9F) on 12 October 2007. Retrieved 25 April 2007.

1. **[^](#cite_ref-34)** Ralph D Lorenz; Jonathan I Lunine; Paul G Withers; Christopher P McKay (2001). ["Titan, Mars and Earth: Entropy Production by Latitudinal Heat Transport"](http://sirius.bu.edu/withers/pppp/pdf/mepgrl2001.pdf) (PDF). *[Ames Research Center](/source/Ames_Research_Center), University of Arizona Lunar and Planetary Laboratory*. [Archived](https://web.archive.org/web/20191009162319/http://sirius.bu.edu/withers/pppp/pdf/mepgrl2001.pdf) (PDF) from the original on 9 October 2019. Retrieved 21 August 2007.

1. **[^](#cite_ref-moore_35-0)** Moore, Matthew (9 October 2008). ["Messages from Earth sent to distant planet by Bebo"](https://www.telegraph.co.uk/news/newstopics/howaboutthat/3166709/Messages-from-Earth-sent-to-distant-planet-by-Bebo.html). .telegraph.co.uk. [Archived](https://web.archive.org/web/20081011142445/http://www.telegraph.co.uk/news/newstopics/howaboutthat/3166709/Messages-from-Earth-sent-to-distant-planet-by-Bebo.html) from the original on 11 October 2008. Retrieved 9 October 2008.

1. **[^](#cite_ref-sky_36-0)** ["Stars' Faces Beamed Into Space"](http://news.sky.com/skynews/Home/Technology/Bebos-A-Message-from-Earth-Project-Beams-Celebrity-Faces-Into-Space/Article/200810215117103?lpos=Technology_First_Technology_Article_Teaser_Region__3&lid=ARTICLE_15117103_Bebos_A_Message_from_Earth_Project_Beams_Celebrity_Faces_Into_Space). Sky News. 10 October 2008. Retrieved 5 November 2008.{{[cite web](https://en.wikipedia.org/wiki/Template:Cite_web)}}: CS1 maint: deprecated archival service ([link](https://en.wikipedia.org/wiki/Category:CS1_maint:_deprecated_archival_service))

1. **[^](#cite_ref-bebo_37-0)** Sarah Gavin (29 July 2008). ["One Giant Leap For The Bebo Community"](https://web.archive.org/web/20180925232920/https://bebo.com/Press.jsp?PressPageId=7554880862). Bebo. Archived from [the original](http://www.bebo.com/Press.jsp?PressPageId=7554880862) on 25 September 2018. Retrieved 15 November 2008.

1. **[^](#cite_ref-38)** ["MY SINGLES"](https://lauraofficial.com/my-singles). *LAURA PÕLDVERE*. Retrieved 2 March 2026.

## Further reading

Wikimedia Commons has media related to [Gliese 581 c](https://commons.wikimedia.org/wiki/Category:Gliese_581_c).

### News media reports

- Dennis Overbye (12 June 2007). ["A Planet Is Too Hot for Life, but Another May Be Just Right"](https://www.nytimes.com/2007/06/12/science/space/12plan.html). *[The New York Times](/source/The_New_York_Times)*. [Archived](https://web.archive.org/web/20150605045719/http://www.nytimes.com/2007/06/12/science/space/12plan.html) from the original on 5 June 2015. Retrieved 11 July 2009.

- ["Astronomers Find First Earth-like Planet in Habitable Zone"](https://web.archive.org/web/20080828055304/http://eso.org/outreach/press-rel/pr-2007/pr-22-07.html). *[European Southern Observatory](/source/European_Southern_Observatory)*. 25 April 2007. Archived from [the original](http://www.eso.org/outreach/press-rel/pr-2007/pr-22-07.html) on 28 August 2008. Retrieved 20 June 2008.

- ["New 'super-Earth' found in space"](https://news.bbc.co.uk/2/hi/science/nature/6589157.stm). *BBC News*. 25 April 2007. [Archived](https://web.archive.org/web/20120305232748/http://news.bbc.co.uk/2/hi/science/nature/6589157.stm) from the original on 5 March 2012. Retrieved 20 June 2008.

- Than, Ker (24 April 2007). ["Major Discovery: New Planet Could Harbor Water and Life"](http://www.space.com/scienceastronomy/070424_hab_exoplanet.html). *SPACE.com*. [Archived](https://web.archive.org/web/20101224061707/http://www.space.com/scienceastronomy/070424_hab_exoplanet.html) from the original on 24 December 2010. Retrieved 20 June 2008.

- Hazel Muir (25 April 2007). ["'Goldilocks' planet may be just right for life"](https://www.newscientist.com/article/dn11710). New ScientistSpace. [Archived](https://web.archive.org/web/20090418014052/http://www.newscientist.com/article/dn11710) from the original on 18 April 2009. Retrieved 29 August 2017.

- ["Astronomers find first habitable Earth-like planet"](https://web.archive.org/web/20090316004654/http://www.scientificblogging.com/news/astronomers_find_first_habitable_earth_like_planet). Scientificblogging.com. 24 April 2007. Archived from [the original](http://www.scientificblogging.com/news/astronomers_find_first_habitable_earth_like_planet) on 16 March 2009. Retrieved 25 April 2007.

- Ian Sample (24 April 2007). ["'Second Earth' may mean we're not alone"](http://www.hindu.com/thehindu/holnus/008200704250305.htm). *The Hindu*. [Archived](https://web.archive.org/web/20090606170509/http://www.hindu.com/thehindu/holnus/008200704250305.htm) from the original on 6 June 2009. Retrieved 26 April 2007.

- J. R. Minkle (24 April 2007). ["All Wet? Astronomers Claim Discovery of Earth-like Planet"](http://www.sciam.com/article.cfm?articleID=25A261F0-E7F2-99DF-313249A4883E6A86&chanID=sa007). [Scientific American](/source/Scientific_American). [Archived](https://web.archive.org/web/20071013164438/http://www.sciam.com/article.cfm?articleID=25A261F0-E7F2-99DF-313249A4883E6A86&chanID=sa007) from the original on 13 October 2007. Retrieved 26 April 2007.

- ["Distant planet judged possibly habitable"](http://www.world-science.net/othernews/070425-habitable-planet.htm). World Science. 23 April 2007. [Archived](https://web.archive.org/web/20090426064222/http://www.world-science.net/othernews/070425-habitable-planet.htm) from the original on 26 April 2009. Retrieved 4 May 2007.

- ANI (23 April 2007). ["First habitable Earth like planet outside Solar System discovered"](https://web.archive.org/web/20070427014548/http://www.dailyindia.com/show/135806.php/First-habitable-Earth-like-planet-outside-Solar-System-discovered). DailyIndia.com. Archived from [the original](http://www.dailyindia.com/show/135806.php/First-habitable-Earth-like-planet-outside-Solar-System-discovered) on 27 April 2007.

### Non-news media

- ["Artist conceptions of extrasolar planet Gliese 581 c"](http://www.cosmographica.com/cosmo20130812/gliese581c.html). *Cosmographica*. Retrieved 20 June 2008.

- ["The Neighbor: Gliese 581c"](https://web.archive.org/web/20071227124513/http://www.geochemsoc.org/publications/geochemicalnews/gn131apr07/theneighborgliese581c.htm). *The Geochemical Society*. Archived from [the original](http://www.geochemsoc.org/publications/geochemicalnews/gn131apr07/theneighborgliese581c.htm) on 27 December 2007. Retrieved 6 December 2007.

- ["Red, Willing, and Able: 2001 New Scientist article on types of planets likely to be around red dwarf stars"](http://www.kencroswell.com/reddwarflife.html). *KenCroswell.com*. [Archived](https://web.archive.org/web/20080430024151/http://www.kencroswell.com/reddwarflife.html) from the original on 30 April 2008. Retrieved 20 June 2008.

- Nemiroff, R.; Bonnell, J., eds. (2 May 2007). ["Sunrise from the Surface of Gliese 581c"](https://apod.nasa.gov/apod/ap070502.html). *[Astronomy Picture of the Day](/source/Astronomy_Picture_of_the_Day)*. [NASA](/source/NASA). Retrieved 20 June 2008.

## External links

- [Gliese 581 - The "Red Dwarf" and implications for its "earthlike" planet Gliese 581c](http://members.misty.com/don/g581.html) [Archived](https://web.archive.org/web/20101205160305/http://members.misty.com/don/g581.html) 5 December 2010 at the [Wayback Machine](/source/Wayback_Machine)

v t e Gliese 581 system Star Gliese 581 Planets Gliese 581e Gliese 581b Gliese 581c Gliese 581g† Gliese 581d? Gliese 581f† Messages A Message from Earth Hello from Earth † - Disproven Category:Gliese 581 Portal:Astronomy

v t e Extraterrestrial life Events, objects Shergotty meteorite (1865) Nakhla meteorite (1911) Murchison meteorite (1969) Viking lander biological experiments (1976) Allan Hills 77005 (1977) Allan Hills 84001 (1984) Yamato 000593 (2000) CI1 fossils (2011) Signals of interest Misidentified CP 1919 (pulsar) CTA-102 (quasar) Stars KIC 8462852 (unusual light fluctuations) EPIC 204278916 (unusual light fluctuations) VVV-WIT-07 (unusual light fluctuations) HD 164595 signal (unknown origin) Other SHGb02+14a (radio source) Wow! signal (inconclusive) Fast radio burst (unknown origin) BLC1 (radio signal) Life in the universe Earliest known life forms Life on Venus Life on Mars Life on Titan Planetary habitability (list) In Solar System Earth analog Extraterrestrial liquid water Of natural satellites Superhabitable Tholins Proximity To red dwarfs To orange dwarfs To yellow dwarfs To F-type stars To binary stars To neutron stars Zones Galactic Circumstellar Complex life Space missions Beagle 2 Biological Oxidant and Life Detection BioSentinel Curiosity rover Darwin Dragonfly Enceladus Explorer Enceladus Life Finder Europa Clipper ExoMars Rosalind Franklin rover ExoLance EXPOSE Foton-M3 Icebreaker Life Journey to Enceladus and Titan Laplace-P Life Investigation For Enceladus Living Interplanetary Flight Experiment Mars Geyser Hopper Mars sample-return mission Mars 2020 Northern Light Opportunity rover Perseverance rover SpaceX Red Dragon Spirit rover Tanpopo Titan Mare Explorer Venus In Situ Explorer Viking 1 Viking 2 Interstellar communication Active SETI Allen Telescope Array Arecibo message Arecibo Observatory Berkeley SETI Research Center Bracewell probe Breakthrough Initiatives Breakthrough Listen Breakthrough Message Communication with extraterrestrial intelligence Gauss's Pythagorean right triangle proposal Astrolinguistics Lincos language NIROSETI Pioneer plaque Project Cyclops Project Ozma Project Phoenix SERENDIP Search for extraterrestrial intelligence SETI@home setiQuest Voyager Golden Record Water hole Xenolinguistics Hypotheses Cosmic pluralism Directed panspermia Drake equation Extraterrestrial hypothesis Extraterrestrial intelligence Fermi paradox Hypothetical types of biochemistry Interplanetary contamination Kardashev scale Mediocrity principle Non-planetary abiogenesis Panspermia Fermi paradox solutions Aestivation hypothesis Berserker hypothesis Dark forest hypothesis Firstborn hypothesis Great Filter Hart–Tipler conjecture Neocatastrophism Planetarium hypothesis Rare Earth hypothesis Zoo hypothesis (Uniformity of motive) Related topics Ancient astronauts Astrobiology Astroecology Biosignature Brookings Report Definition of life Exotheology Extraterrestrials in fiction Extremophile Hemolithin History of the extraterrestrial life debate List of alleged extraterrestrial beings Nexus for Exoplanet System Science Noogenesis Planetary protection Potential cultural impact of extraterrestrial contact Post-detection policy San Marino Scale Technosignature UFO religion Xenoarchaeology

[Portal](https://en.wikipedia.org/wiki/Wikipedia:Contents/Portals):
- [Outer space](https://en.wikipedia.org/wiki/Portal:Outer_space)

---
Adapted from the Wikipedia article [Gliese 581c](https://en.wikipedia.org/wiki/Gliese_581c) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Gliese_581c?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.