Gliese 581 c (IPA: [ˈgliːzə]) is a "super-earth" extrasolar planet orbiting the red dwarf star Gliese 581.^[3] It appears to be the first extrasolar planet discovered in the hypothetical habitable zone surrounding its star, where surface temperatures might maintain liquid water^[3][4] and therefore be suitable for life as known on Earth. The planet is astronomically close, at 20.5 light years (194 trillion km or 120 trillion miles) from Earth in the direction of the constellation of Libra.^[2] Its star is identified as Gliese 581 by its number in the Gliese Catalogue of Nearby Stars; with respect to Earth it is the 87th closest star system.^[5] The orbital period is the time it takes a planet (or another object) to make one full orbit. ... Look up day in Wiktionary, the free dictionary. ... Inclination in general is the angle between a reference plane and another plane or axis of direction. ... In mathematics (in particular geometry and trigonometry) and all natural sciences (including astronomy, geophysics, etc), the angular distance (or angular separation) between two point objects, as observed from a location different from either of these objects, is the size of the angle between the two directions originating from the observer... A milliarcsecond (m, mas) , or a thoundsanth of an arcsecond. ... In astrodynamics, the longitude of the periapsis (symbolized ) of an orbiting body is the longitude (measured from the point of the vernal equinox) of periapsis (closest approach to the central body). ... A diagram of Keplerian orbital elements. ... A diagram of Keplerian orbital elements. ... The Julian day or Julian day number (JDN) is the (integer) number of days that have elapsed since Monday, January 1, 4713 BC in the proleptic Julian calendar [1]. That day is counted as Julian day zero. ... Unsolved problems in physics: What causes anything to have mass? The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. Mass is the property of a physical object that quantifies the amount of matter and energy it is equivalent to. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Circle illustration In classical geometry, a radius (plural: radii) of a circle or sphere is any line segment from its center to its boundary. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... In physics, density is mass m per unit volume V. For the common case of a homogeneous substance, it is expressed as: where, in SI units: ρ (rho) is the density of the substance, measured in kg·m-3 m is the mass of the substance, measured in kg V is... The U.S. National Prototype Kilogram, which currently serves as the primary standard for measuring mass in the U.S. It was assigned to the United States in 1889 and is periodically recertified and traceable to the primary international standard, The Kilogram, held at the Bureau International des Poids et... The cubic meter (symbol m³) is the SI derived unit of volume. ... Fig. ... The kelvin (symbol: K) is a unit increment of temperature and is one of the seven SI base units. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 4 is the 94th day of the year in the Gregorian calendar (95th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... Stéphane Udry is an astronomer at the Geneva Observatory in Switzerland. ... Any planet is an extremely faint light source compared to its parent star. ... 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. ... Gliese 581 c, a Super-Earth and its star as rendered in Celestia. ... An extrasolar planet, or exoplanet, is a planet beyond the Solar System. ... Red Dwarf is a British science fiction comedy franchise, the primary form of which comprises eight series of a post-watershed television sitcom that ran on BBC2 between 1988 and 1999, and which has achieved a global cult following. ... 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. ... Gliese 581 is an M2. ... In astronomy a habitable zone (HZ) is a region of space where conditions are favorable for life, as it can be found on earth. ... The historical temperature record shows the fluctuations of the temperature of the atmosphere and the oceans throughout history, and in particular since 1850. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... A light-year, symbol ly, is the distance light travels in one year: exactly 9. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ... Libra (IPA: , Latin: , symbol , Unicode ) is a constellation of the zodiac. ... In astronomy, many stars are referred to simply by catalogue numbers. ...

Gliese 581 c is the first extrasolar planet believed to have a surface temperature similar to that of Earth. It is the smallest extrasolar planet around a main sequence star discovered to date.^[3] Hertzsprung-Russell diagram The main sequence of the Hertzsprung-Russell diagram is the curve where the majority of stars are located in this diagram. ...

Discovery

The discovery of the planet by the team of Stéphane Udry of the Geneva Observatory in Switzerland was announced on April 24, 2007. The team used the HARPS instrument (an echelle spectrograph) on the European Southern Observatory 3.6 m Telescope in La Silla, Chile. The team employed the radial velocity technique. The team now intends to use the Canadian-built MOST space telescope to conduct follow-up studies of the planet if it is a transiting planet. Stéphane Udry is an astronomer at the Geneva Observatory in Switzerland. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... The High Accuracy Radial velocity Planet Searcher (HARPS) is a high-precision echelle spectrograph installed in 2002 with first light achieved February 2003 on ESOs 3. ... An Échelle Grating (échelle= french for stairs/ladder) is a type of diffraction grating which is characterised by a relatively low grooves density but are optimised for high diffraction orders. ... The European Southern Observatory (ESO) is an international astronomical organisation, composed and supported by ten countries from the European Union plus Switzerland. ... The ESO 3. ... La Silla Observatory is an astronomical observatory in Chile with eighteen telescopes. ... Radial velocity is the velocity of an object in the direction of the line of sight. ... The Microvariability and Oscillations of STars telescope or the MOST space observatory is Canadas first and (as of mid-2005) only space telescope. ... Deimos transits the Sun, as seen by Mars Rover Opportunity on March 4, 2004 The word transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at...

The team has released a paper dated April 27, 2007 which will be published in an edition of the journal Astronomy and Astrophysics.^[6] In the paper they also announce the discovery of another planet in the system, Gliese 581 d, with a minimum mass of 7.7 Earth masses and a semi-major axis of 0.25 astronomical units. April 27 is the 117th day of the year (118th in leap years) in the Gregorian calendar, with 248 days remaining. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... Astronomy and Astrophysics (often referred to as A&A) is a European Journal, publishing papers on theoretical, observational and instrumental astronomy and astrophysics. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ...

Physical characteristics

Mass

The existence of Gliese 581 c and its mass has been measured by the Radial Velocity Method or the "wobble-effect" method of detecting exoplanets. The mass of a planet is calculated by the small periodical movements around a common centre of mass between the host star Gliese 581 and its planets. Because the "wobbling" of Gliese 581 is a result of all planets in its system, the calculation of the mass of Gliese 581 c depends on the presence of other planets in the Gliese 581 system and on the inclination of the orbital plane with respect to Earth. Using the known minimum mass of the previously detected Gliese 581 b, and assuming the existence of Gliese 581 d, Gliese 581 c has a mass at least 5.03 times that of Earth. The mass of the planet cannot be very much larger than this or the system becomes dynamically unstable.^[6] Any planet is an extremely faint light source compared to its parent star. ... Infrared Image of a possible extrasolar planet (lower left) in the Constellation Taurus, taken by the Hubble Space Telescope. ... Gliese 581 is an M2. ... Gliese 581 b is an extrasolar planet orbiting the star Gliese 581. ... Gliese 581 d is an extrasolar planet orbiting the red dwarf star Gliese 581. ...

Radius

If it is a rocky planet with a large iron core, Gliese 581 c has a radius approximately 50% larger than that of Earth, according to Udry's team.^[6][7] Gravity on such a planet's surface would be approximately 2.2 times as strong as on Earth. The rocky side of a mountain creek near Orosí, Costa Rica. ... Gravity is a force of attraction that acts between bodies that have mass. ...

If Gliese 581 c is an icy and/or watery planet, its radius would still be less than 2 times that of Earth, even with a very large outer hydrosphere, according to density models compiled by Diana Valencia and her team for Gliese 876 d.^[8] Gravity on the surface of such an icy and/or watery planet would be at least 1.25 times as strong as on Earth. Snowflakes by Wilson Bentley, 1902 Ice is the name given to any one of the 14 known solid phases of water. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... The movement of water around, over, and through the Earth is called the water cycle, a key process of the hydrosphere. ... Gliese 876 d is an extrasolar planet orbiting the red dwarf star Gliese 876. ...

With the Radial Velocity method of detection, it is not possible to measure the radius of an exoplanet. The real value may be anything between the two extremes calculated by density models outlined above.^[9] If the planet transits the star as seen from our direction, the radius should be measurable, although with some uncertainty. Udry's team intends to use the Canadian-built MOST space telescope to look for a transit of the planet before its host star. A transit measurement could very well determine whether Gliese 581 c is a primarily rocky or watery object. Radial velocity is the velocity of an object in the direction of the line of sight. ... The Microvariability and Oscillations of STars telescope or the MOST space observatory is Canadas first and (as of mid-2005) only space telescope. ...

Age

The Gliese 581 system is estimated to be around 4.3 billion years old.^[10] By comparison, the Solar System is estimated to be 4.57 billion years old. Major features of the Solar System (not to scale; from left to right): Pluto, Neptune, Uranus, Saturn, Jupiter, the asteroid belt, the Sun, Mercury, Venus, Earth and its Moon, and Mars. ... The theories concerning the formation and evolution of the Solar System are complex and varied, interweaving various scientific disciplines, from astronomy and physics to geology and planetary science. ...

Orbit

Gliese 581 c has an orbital period ("year") of 13 Earth days^[2] and its orbital radius is only about 7% that of the Earth, about 11 million km^[11], while the Earth is 150 million kilometres from the Sun^[12]. 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 ^{[6] [7]}. This proximity also means that the primary star appears several times larger for an observer standing on the planet's surface looking at the sky than the Sun appears to be from Earth's surface. The orbit is inclined to 84 degrees from our vantage point meaning the orbit is almost edge on but a transit would be extremley difficult to detect due to the planet's small size. The star is about 3 times the size of Jupiter. The orbital period is the time it takes a planet (or another object) to make one full orbit. ... KM, Km, or km may stand for: Khmer language (ISO 639 alpha-2, km) Kilometre Kinemantra Meditation Knowledge management KM programming language KM Culture, Korean Movie Maker. ... The Sun (Latin: Sol) is the star at the center of the Solar System. ...

Temperature and habitability

Scale comparison of the relative sizes of the Earth and Gliese 581 c, assuming Gliese 581 c is a rocky body

Image File history File links Size of this preview: 666 × 408 pixelsFull resolution (666 × 408 pixel, file size: 139 KB, MIME type: image/png) Original diagram created by User:Latitude0116 (Image:Gliese581cEarthComparison. ... Image File history File links Size of this preview: 666 × 408 pixelsFull resolution (666 × 408 pixel, file size: 139 KB, MIME type: image/png) Original diagram created by User:Latitude0116 (Image:Gliese581cEarthComparison. ... Adjectives: Terrestrial, Terran, Telluric, Tellurian, Earthly Atmosphere Surface pressure: 101. ...

Temperature

Using the measured stellar luminosity of Gliese 581 of 0.013 times that of our Sun, it is possible to calculate Gliese 581 c equilibrium surface temperature, which does not take into account a possible atmosphere. According to Udry's team the equilibrium temperature for Gliese 581 c is −3° C / 26.6° F, assuming an albedo (how much light is reflected by the planet's surface) such as Venus (0.64) and 40°C / 104° F for an Earth-like albedo (0.35).^[6][2] The actual temperature on the surface also depends on the planet's atmosphere, which remains unknown. Xavier Delfosse of the research team expects that the actual surface temperatures will be hotter; for instance, the corresponding calculation for Earth yields an "effective surface temperature" of 256 K (−17 °C), yet Earth's true surface is 32 K warmer (an average of 288 K (15 °C)) due to the greenhouse effect. Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Albedo is the ratio of reflected to incident electromagnetic radiation power. ... Celsius is, or relates to, the Celsius temperature scale (previously known as the centigrade scale). ... Fahrenheit is a temperature scale named after the German physicist Daniel Gabriel Fahrenheit (1686–1736), who proposed it in 1724. ... Albedo is the ratio of reflected to incident electromagnetic radiation power. ... View of Jupiters active atmosphere, including the Great Red Spot. ... A schematic representation of the exchanges of energy between outer space, the Earths atmosphere, and the Earth surface. ...

Liquid water

Gliese 581 c is within the habitable zone where water—a necessary ingredient for life as we know it—could exist.^[3][13] However, no direct evidence has been found. Techniques like the one used to measure HD 209458 b could be applied to determine the existence of water vapor in an extrasolar planet's atmosphere, but only in the rare case of a planet with an orbit including transit directly between its star and our planet, which Gliese 581c is not known to do. In astronomy a habitable zone (HZ) is a region of space where conditions are favorable for life, as it can be found on earth. ... Impact from a water drop causes an upward rebound jet surrounded by circular capillary waves. ... For other uses, see Life (disambiguation). ... ... View of Jupiters active atmosphere, including the Great Red Spot. ... 2003 Transit of Mercury The term transit or astronomical transit has two meanings in astronomy: A transit is the astronomical event that occurs when one celestial body appears to move across the face of another celestial body, as seen by an observer at some particular vantage point. ...

Tidal forces

Because of its small separation from Gliese 581, the planet is very likely to be tidally locked, with one hemisphere always day (facing the star) and the other always night (facing away).^[14] The lit hemisphere would be extremely hot and the dark hemisphere extremely cold, while the narrow terminator or "twilight zone" between them might have a moderate climate more suitable for life.^[15] Tidal locking makes one side of an astronomical body always face another, like the Moon facing the Earth. ... The word hemisphere literally means half sphere or half ball; when used in the singular form, it refers to one of the halves of a spherical object. ... World map with terminator (April) A composite image showing the terminator dividing night from day, running across Europe and Africa. ... Understanding planetary habitability is partly an extrapolation of the Earths conditions, as it is the only planet currently known to support life. ...

Theoretical models predict that 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. Alternatively, an atmosphere large enough to be stable would circulate the heat more evenly, allowing for a wider habitable area on the surface.^[16] However, it remains unknown if water and/or carbon dioxide are even present on the surface of Gliese 581 c. A compound is an area of land that is surrounded by fences, walls, or barbed wire and is used for a particular purpose, especially an area containing buildings and where the entry and exit of people is controlled. ... This article describes water from a scientific and technical perspective. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... An ice cap is a dome-shaped ice mass that covers less than 50,000 km² of land area (usually covering a highland area). ...

Further study

Gliese 581 c presents several challenges for study or exploration. It has not been directly observed, and the development of equipment sensitive enough to look for signs of life will take several years.^[17] However, according to the research-team member Xavier Delfosse:

Because of its temperature and relative proximity, this planet will most probably be a very important target of the future space missions dedicated to the search for extraterrestrial life. On the treasure map of the universe, one would be tempted to mark this planet with an X.^[17][7] A 1967 Soviet Union 16 kopeks stamp. ...

Several astronomers have suggested that the earthlike properties of Gliese 581 c and its relative proximity (20.5 light-years away) would make it a potential target for any future interstellar probe project.^[18][2] This article or section does not cite its references or sources. ...

See also

• Planetary habitability
• Habitable zone
• Goldilocks phenomenon
• Interstellar travel

Image File history File links WikiNews-Logo. ... Wikinews is a free-content news source and a project of the Wikimedia Foundation. ... Image File history File links Commons-logo. ... The Wikimedia Commons (also called Wikicommons) is a repository of free content images, sound and other multimedia files. ... Understanding planetary habitability is partly an extrapolation of the Earths conditions, as it is the only planet currently known to support life. ... In astronomy a habitable zone (HZ) is a region of space where conditions are favorable for life, as it can be found on earth. ... It has been suggested that this article or section be merged into Habitable zone. ... Interstellar space travel is unmanned or manned travel between stars, though the term usually denotes the latter. ...

References

2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... April 25 is the 115th day of the year in the Gregorian calendar (116th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 25 is the 115th day of the year in the Gregorian calendar (116th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 29 is the 119th day of the year (120th in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... February 24 is the 55th day of the year in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 29 is the 119th day of the year (120th in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st 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. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 25 is the 115th day of the year in the Gregorian calendar (116th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... May 10 is the 130th day of the year (131st in leap years) in the Gregorian calendar. ... Todays San Francisco Chronicle was founded in 1865 as The Daily Dramatic Chronicle by teenage brothers Charles de Young and Michael H. de Young. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... November 7 is the 311th day of the year (312th in leap years) in the Gregorian Calendar, with 54 days remaining. ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 25 is the 115th day of the year in the Gregorian calendar (116th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 25 is the 115th day of the year in the Gregorian calendar (116th in leap years). ... The New York Times is an internationally known daily newspaper published in New York City and distributed in the United States and many other nations worldwide. ...

Selected media articles

• Hazel Muir (April 25, 2007). 'Goldilocks' planet may be just right for life. NewScientistSpace.
• Astronomers find first habitable Earth-like planet. Scientificblogging.com (April 24, 2007).
• Ian Sample (April 24, 2007). 'Second Earth' may mean we're not alone. The Hindu.
• J.R. Minkle (April 24, 2007). All Wet? Astronomers Claim Discovery of Earth-like Planet. Scientific American.
• Distant planet judged possibly habitable. World Science (April 23, 2007).
• ANI (April 23, 2007). First habitable Earth like planet outside Solar System discovered. DailyIndia.com.
• Joe Campbell (April 26, 2007). Meet the neighbours. BBC Magazine.

April 25 is the 115th day of the year in the Gregorian calendar (116th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 24 is the 114th day of the year in the Gregorian calendar (115th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 23 is the 113th day of the year in the Gregorian calendar (114th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 23 is the 113th day of the year in the Gregorian calendar (114th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ... April 26 is the 116th day of the year in the Gregorian calendar (117th in leap years). ... 2007 (MMVII) is the current year, a common year starting on Monday of the Gregorian calendar and the AD/CE era. ...

External links

• ESO 22/07 Astronomers Find First Earth-like Planet in Habitable Zone
• Space.com: Major Discovery: New Planet Could Harbor Water and Life
• Planet : Gl 581 c
• Red, Willing, and Able: 2001 New Scientist article on types of planets likely to be around red dwarf stars
• New 'Super Earth' found in space
• Artistic Image (APOD)
• Artist conceptions of extrasolar planet Gliese 581 c
• Gliese 581 c (french)
• Speculation about geology/geochemistry of Gliese 581c The Geochemical Society