- Gliese 581 d
Planetbox begin
name = Gliese 581 dPlanetbox image
caption = An artist's impression of Gliese 581 d and speculative moons.Planetbox star
star =Gliese 581
constell = Libra
RA = RA|15|19|26
DEC = DEC|−07|43|20
dist_ly = 19.9
dist_pc = 6.12
class = M2.5V Planetbox orbit
period = 83.22730 ± 0.65845cite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2007A%26A...469L..43U&db_key=AST&nosetcookie=1|title=The HARPS search for southern extra-solar planets. XI. Super-Earths (5 and 8 M⊕) in a 3-planet system|author=Udry, S.; Bonfils, X.; Delfosse, X.; Forveille, T.; Mayor, M.; Perrier, C.; Bouchy, F.; Lovis, C.; Pepe, F.; Queloz, D.; Bertaux, J.-L.|journal=Astronomy and Astrophysics |volume=469|issue=3|year=2007|pages=L43 – L47|doi=10.1051/0004-6361:20077612|accessdate=2008-08-18]
semimajor = 0.2525 ± 0.013
eccentricity = 0.12118 ± 0.12034Planetbox character
mass_earth = >7.804 ± 0.69 Planetbox discovery
discovery_date =24 April 2007
discoverers = Udry et al.
discovery_method =Radial velocity
discovery_site = flag|Switzerland
discovery_status = PublishedGliese 581 d (pronEng|ˈgliːzə) is an
extrasolar planet approximately 20light-year s away in theconstellation of Libra. Because of its mass, the planet is classified as asuper-Earth planet. Because the planet orbits in the outer edge of its parent star'shabitable zone , it is thought that the planet may be similar toEarth .Discovery
The planet was discovered by the team of
Stéphane Udry of theGeneva Observatory inSwitzerland using theHARPS instrument on theEuropean Southern Observatory 3.6meter telescope inLa Silla ,Chile on 24April 2007 . Udry's team employed theradial velocity technique, in which the size andmass of aplanet are determined based on the small perturbations it induces in its parent star’sorbit viagravity .The team is confident that the planet exists but recognizes that unlikely events could mimic its existence. They believe the issue will be settled by upcoming studies.
Dynamical simulations of the Gliese 581 system assuming that the orbits of the three planets are coplanar show that the system becomes unstable if its component masses are so high as to correspond to an overall inclination angle of 10° or less. [cite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2008A%26A...479..277B&db_key=AST&nosetcookie=1|author=Beust, H. et al.|title=Dynamical evolution of the Gliese 581 planetary system|journal=
Astronomy and Astrophysics |volume=479|issue=1|year=2008|pages=277–282|doi=10.1051/0004-6361:20078794|accessdate=2008-08-20] For Gliese 581 d, the upper bound of its mass must be half that of 581 b; that is, 581 d's maximum is 45 Earth masses. [Dividing the m sin i by "Sin(10/180 * PI)" on a radian-configured processor.] At this mass it must be held together with a central heavy-element core like Saturn and maybe evenHD 149026 b .Climate and habitability
Although Gliese 581 d orbits outside the theoretical
habitable zone of its star, scientists surmise that conditions on the planet may be conducive to supporting life. [ [http://www.space.com/scienceastronomy/070618_mm_gliese_581d.html SPACE.com - Hopes Dashed for Life on Distant Planet ] ] [cite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2007A%26A...476.1365V&db_key=AST&nosetcookie=1|title=The Habitability of Super-Earths in Gliese 581|author=von Bloh, W.; Bounama, C.; Cuntz, M.; Franck, S.|journal=Astronomy & Astrophysics |volume=476|pages=1365 – 1371|doi=10.1051/0004-6361:20077939|accessdate=2008-08-18] Scientists originally believed that Gliese 581 d would be too cold forliquid water to exist, and therefore could not supportlife in forms as existing on Earth. However, since Earth's temperature would be about -19°C without any greenhouse gases,Fact|date=September 2008 and due to a theorizedgreenhouse effect of Gliese 581 d, research now suggests thatatmospheric conditions on the planet could createtemperature s at which liquid water can exist, and therefore the planet may be capable of supporting life.Fact|date=September 2008References
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