Gliese 581 (IPA: [ˈgliːzə]) is an M2.5V red dwarf star located 20.4 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, and with respect to Earth, is the 87th known closest star system.^[4] The star system recently gained attention after Gliese 581 c, the first low mass extrasolar planet found to be in its star's habitable zone, was discovered in April 2007^[5]. In astronomy, an epoch is a moment in time for which celestial coordinates or orbital elements are specified. ... This article does not cite any references or sources. ... Libra (IPA: , Latin: , symbol , Unicode ) is a constellation of the zodiac. ... Equatorial Coordinates Right ascension (abbrev. ... In astronomy, declination (abbrev. ... The apparent magnitude (m) of a star, planet or other celestial body is a measure of its apparent brightness as seen by an observer on Earth. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... In astronomy, the color index is a simple numerical expression that determines the color of an object, which in the case of a star gives its temperature. ... This article or section contains a plot summary that is overly long or excessively detailed. ... BY Draconis variables are main sequence variable stars of late spectral types, usually K or M. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other chromospheric activity. ... Illustration of the use of optical wavelength interferometry to determine precise positions of stars. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... kilometre per second is an SI derived unit of both speed (scalar) and velocity (vector), signified by the symbol km/s or km s-1. ... The proper motion of a star is the motion of the position of the star in the sky (the change in direction in which we see it, as opposed to the radial velocity) after eliminating the improper motions of the stars, which affect their measured coordinates but are not real... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... This does not adequately cite its references or sources. ... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... Distance is a numerical description of how far apart objects are at any given moment in time. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... A parsec is the distance from the Earth to an astronomical object which has a parallax angle of one arcsecond. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... This article or section is in need of attention from an expert on the subject. ... In astronomy, the solar mass is a unit of mass used to express the mass of stars and larger objects such as galaxies. ... Remote Authentication Dial In User Service (RADIUS) is an AAA (authentication, authorization and accounting) protocol for applications such as network access or IP mobility. ... In astronomy, the solar radius is a unit of length used to express the size of stars and larger objects such as galaxies. ... This article does not cite any references or sources. ... The solar luminosity, , is a unit of luminosity (power emitted in the form of photons) conventionally used by astronomers to give the luminosities of stars. ... Fig. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... The globular cluster M80. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... A year (from Old English gÄ“r) is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ... A star catalogue, or star catalog, is an astronomical catalog that lists stars. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... In astronomy, many stars are referred to simply by catalogue numbers. ... The Hipparcos and Tycho Catalogues (Tycho-1) are the primary products of the European Space Agencys astrometric mission, Hipparcos. ... SIMBAD (the Set of Identifications, Measurements, and Bibliography for Astronomical Data) is a database of astronomical information about objects within the Milky Way. ... Articles with similar titles include the NATO phonetic alphabet, which has also informally been called the “International Phonetic Alphabet”. For information on how to read IPA transcriptions of English words, see IPA chart for English. ... In astronomy, stellar classification is a classification of stars based initially on photospheric temperature and its associated spectral characteristics, and subsequently refined in terms of other characteristics. ... For the type of star, see Red dwarf. ... A light-year or lightyear (symbol: ly) is a unit of measurement of length, specifically the distance light travels in vacuum in one year. ... Beta Librae (β Lib / β Librae) is the brightest star in the constellation Libra. ... This article does not cite any references or sources. ... Libra (IPA: , Latin: , symbol , Unicode ) is a constellation of the zodiac. ... Sol redirects here. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... This article or section needs additional references or sources to improve its verifiability. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...

It has since been shown that Gliese 581 c will almost certainly have a runaway greenhouse effect, and would not be habitable. However, Gliese 581 d is near the outer edge of the habitable zone. ^[6] Observations suggest that the star has at least three planets. Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ...

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. A star catalogue, or star catalog, is an astronomical catalog that lists stars. ... Wilhelm Gliese (June 21, 1915 – June 12, 1993) was a German astronomer. ... To meet Wikipedias quality standards, this article or section may require cleanup. ... Variable stars are named using a variation on the Bayer designation format of Identifier <genitive of constellation>. In previous centuries few variable stars were known, so it seemed reasonable to use the letters of the Roman alphabet, starting from the letter R so as to avoid confusion with letter spectral... Sirius B redirects here. ... Procyon (α CMi / α Canis Minoris / Alpha Canis Minoris) is the brightest star in the constellation Canis Minor and the eighth brightest star in the nighttime sky. ...

Gl 581 is wrongly classified as a BY Draconis variable in the General Catalogue of Variable Stars, where the reference to the study of the star that led to its inclusion in the General Catalogue clearly shows no evidence of variability, least of all data indicative of BY Draconis variability. The data is well within the expected noise level of data discovered in this way^[7]. Both the ASAS-3 data and Hipparcos Epoch Photometry show the star to be stable to at least 0.1 magnitudes (the approximate noise limit of these respective surveys for this object) both in amplitude and in mean magnitude over time, and no real evidence exists for classical variability having ever been seen in this star, least of all formal evidence of BY Draconis variability (such as a periodic sinusoidal light curve representing the motion of any starspot as it moves due to the stellar rotation). BY Draconis variables are main sequence variable stars of late spectral types, usually K or M. They exhibit variations in their luminosity due to rotation of the star coupled with star spots, and other chromospheric activity. ...

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. From the apparent magnitude and distance, we can estimate a visual luminosity of 0.2% of that of the Sun. However, a red dwarf such as Gliese 581 radiates primarily in the near infrared, with peak emission at a wavelength of roughly 830 nanometres (estimated using Wien's displacement law, which assumes the star radiates as a blackbody), so such an estimate will underestimate the star's total luminosity. (For comparison, the peak emission of the Sun is roughly 530 nanometres, in the middle of the visible part of the spectrum). When radiation over the entire spectrum is taken into account (not just the part that humans are able to see), something known as the bolometric correction, this star has a bolometric luminosity 1.3% of the Sun's total luminosity^[2]. 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 prosaically, the habitable zone. Image of two girls in mid-infrared (thermal) light (false-color) Infrared (IR) radiation is electromagnetic radiation of a wavelength longer than that of visible light, but shorter than that of radio waves. ... A nanometre (American spelling: nanometer, symbol nm) is a unit of length in the metric system, equal to one thousand-millionth of a metre, which is the current SI base unit of length. ... Wiens displacement law is a law of physics that states that there is an inverse relationship between the wavelength of the peak of the emission of a black body and its temperature. ... As the temperature decreases, the peak of the black body radiation curve moves to lower intensities and longer wavelengths. ... In astronomy, absolute magnitude is the apparent magnitude, m, an object would have if it were at a standard luminosity distance away from us, in the absence of interstellar extinction. ... The solar luminosity, , is a unit of luminosity (power emitted in the form of photons) conventionally used by astronomers to give the luminosities of stars. ... It has been suggested that this article or section be merged into Habitable zone. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ...

Planetary system

Diagram of the Gliese 581 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.^[8] The latter is notable as it is the smallest planet yet discovered in the habitable zone of another star, making it the most "earthlike" exoplanet found to date. Observations of the star also revealed the possibility of a third planet with a mass of roughly 7.7 Earths, or half a Uranus, and an orbit of 84 Earth days. For other uses, see Jupiter (disambiguation). ... Look up day in Wiktionary, the free dictionary. ... The astronomical unit (AU or au or a. ... Gliese 581 b is an extrasolar planet orbiting the star Gliese 581. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ... Image File history File links Size of this preview: 611 × 599 pixelsFull resolution (1044 × 1024 pixel, file size: 79 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... Image File history File links Size of this preview: 611 × 599 pixelsFull resolution (1044 × 1024 pixel, file size: 79 KB, MIME type: image/png) File historyClick on a date/time to view the file as it appeared at that time. ... A planet (from the Greek &#960;&#955;&#945;&#957;&#942;&#964;&#951;&#962;, planetes or wanderers) is a body of considerable mass that orbits a star and that produces very little or no energy through nuclear fusion. ... STAR is an acronym for: Organizations Society of Ticket Agents and Retailers], the self-regulatory body for the entertainment ticket industry in the UK. Society for Telescopy, Astronomy, and Radio, a non-profit New Jersey astronomy club. ... For other uses, see Neptune (disambiguation). ... Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ...

Gliese 581 b

Main article: 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 b is an extrasolar planet orbiting the star Gliese 581. ... This article or section is in need of attention from an expert on the subject. ...

Gliese 581 c

Main article: Gliese 581 c

Gliese 581 c is believed by some to be a rocky planet with a radius 1.5 times that of Earth. A direct measurement of the radius cannot be taken because the planet is not a transiting object. With a minimum mass of roughly five times Earth - or one third that of Neptune - Gliese 581 c orbits just within the habitable zone of its parent star. The mean blackbody surface temperature has been estimated to lie between -3 °C (for a Venus-like albedo) and 40 °C (for an Earth-like albedo),^[8] , however, the temperatures could be much higher (about 500 degress Celsius) due to a runaway greenhouse effect akin to that of Venus. ^[6] Some believe the system may have 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 (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... It has been suggested that Goldilocks phenomenon be merged into this article or section. ... Albedo is the ratio of reflected to incident electromagnetic radiation. ... Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ... Planetary migration is the act of a stellar satellite altering its orbital parameters, especially semi-major axis, through various means during its lifetime. ... In astronomy or planetary physics, the frost line refers to a particular distance in the solar nebula from the central protosun where it is cool enough for hydrogen compounds such as water, ammonia, and methane to condense into solid ice grains. ...

Gliese 581 d

Main article: Gliese 581 d

Gliese 581 d has a lower mass limit of about 7.7 times the Earth (about half the mass of Uranus) and orbits its star in 84 days. It orbits on the outer edge of the habitable zone of its star, which makes it a potential candidate for being able to support life.^[6] Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ...

See also

Wikinews has related news:

First earthlike planet outside solar system discovered

• List of stars with confirmed extrasolar planets

Image File history File links WikiNews-Logo. ... Wikinews is a free-content news source and a project of the Wikimedia Foundation. ... For a list of brown dwarfs, including those orbiting stars, see list of brown dwarfs. ...

References

• "Major Discovery: New Planet Could Harbor Water and Life"
• Sol Station: Gliese 581 / HO Librae
• BBC News report
• CTV News Report

Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 116th day of the year (117th in leap years) in the Gregorian calendar. ... Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 35th day of the year in the Gregorian calendar. ... The Research Consortium on Nearby Stars (RECONS) is a project to investigate the stars nearest to the Solar System - those within 10 parsecs (32. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 149th day of the year (150th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 149th day of the year (150th in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 242nd day of the year (243rd in leap years) in the Gregorian calendar. ... Year 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... is the 162nd day of the year (163rd in leap years) in the Gregorian calendar. ... Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ...

External links

• Extrasolar Planets Encyclopaedia: Gl 581
• SIMBAD: V* HO Lib -- Variable Star
• All Wet? Astronomers Claim Discovery of Earth-like Planet, Scientific American
• Position of Gliese 581 marked on local space. (Top right corner)
• Photo of Constellation Libra with Gliese 581
• Artist conceptions of planets of Gliese 581
• GLIESE 581 c (french)
• Speculation about geology/geochemistry of Gliese 581c The Geochemical Society
• Computer models suggest planetary and extrasolar planet atmospheres - A gas, gas, gas Washington University in St. Louis

Scientific American is a popular-science magazine, published (first weekly and later monthly) since August 28, 1845, making it the oldest continuously published magazine in the United States. ... Gliese 581 b is an extrasolar planet orbiting the star Gliese 581. ... Gliese 581 c (IPA: ) is a super-earth extrasolar planet orbiting the red dwarf star Gliese 581. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ...