HD 209458
903655
224830670
2008-07-10T16:39:56Z
Kbdankbot
6505923
Robot - move category per [[WP:CFD|CFD]] [[Wikipedia:Categories for discussion/Log/2008 July 2|2008 July 2]]
{{Starbox begin
| name=HD 209458 }}
{{Starbox image
| image=[[Image:Pegasus HD209458 location.png|250px]]
| caption=The red circle shows the location of HD 209458 in Pegasus. }}
{{Starbox observe
| epoch=J2000
| ra=22<sup>h</sup> 03<sup>m</sup> 10.8<sup>s</sup>
| dec=+18° 53′ 04″
| appmag_v=7.65
| constell=[[Pegasus (constellation)|Pegasus]] }}
{{Starbox character
| class=F8-G0 V
| b-v=0.59
| u-b=
| variable=Planetary transit }}
{{Starbox astrometry
| radial_v=-14.8
| prop_mo_ra=28.90
| prop_mo_dec=-18.37
| gal_lat=-28.5269
| gal_lon=76.7535
| parallax=21.24
| p_error=1.00
| dist_ly=154
| dist_pc=47.1
| absmag_v=4.29 }}
{{Starbox detail
| mass=1.1
| radius=1.2
| luminosity=1.61
| temperature=6000
| metal=109%
| rotation=14.4 days
| age=4-7 × 10<sup>9</sup> }}
{{Starbox catalog
| names=[[Bonner Durchmusterung|BD]] +18°4917, [[Smithsonian Astrophysical Observatory Star Catalog|SAO]] 107623, V376 Peg, [[Hipparcos catalogue|HIP]] 108859. }}
{{Starbox reference
| Simbad=HD+209458 }}
{{Starbox end}}
'''HD 209458''' is an 8th [[apparent magnitude|magnitude]] [[star]] in the [[constellation]] [[Pegasus (constellation)|Pegasus]]. It is very similar to our [[Sun]], and it is classified as a [[yellow dwarf]] ([[spectral classification|spectral class]] G0 V). Because it is located at a distance of about 150 [[light year]]s, it is not visible to the unaided eye. With good [[binoculars]] or small [[telescope]] it should be easily detectable.
[[Image:HD209458.jpg|thumb|left|HD 209458]]
In [[1999]] two teams working independently (one team consisted of astronomers at the [[Geneva Observatory]], the [[Harvard-Smithsonian Center for Astrophysics]], and the [[Wise Observatory]]; the second group was the [[California and Carnegie Planet Search]] team) discovered an [[extrasolar planet]] orbiting the star by using the [[radial velocity]] [[planet]] search method. Soon after the discovery, separate teams led by [[David Charbonneau]] and [[Gregory W. Henry]] were able to detect a [[transit (astronomy)|transit]] of the planet across the surface of the star making it the first known transiting extrasolar planet. The planet received the designation ''[[HD 209458 b]]''.
Because the planet transits the star, the star is dimmed by about 2% every 3.5 days making it an [[variable star#Extrinsic variables|extrinsic variable]]. The [[variable star]] designation for HD 209458 is '''V376 Pegasi'''. It is the [[prototype]] of the V376 Pegasi variables, all of which show transits by a planet.[http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/vartype.txt]
== Planetary system ==
[[HD 209458 b]] is an extrasolar planet that orbits the Sun-like star HD 209458 in the constellation Pegasus. [[Astronomical spectroscopy|Spectroscopic]] studies first revealed the presence of a planet around HD 209458 on [[November 5]] [[1999]]. The planet is now under even more public scrutiny with the announcement that its atmosphere contains water vapor. Astronomers had made careful [[photometry (astronomy)|photometric]] measurements of several stars known to be orbited by planets, in the hope that they might observe a dip in brightness caused by the [[astronomical transit|transit]] of the planet across the star's face. This would require the planet's orbit to be inclined such that it would pass between the Earth and the star, and previously no transits had been detected.
Travis Barman at Lowell Observatory in Flagstaff, Arizona, analyzed the emision spectrum of this planet, and believes that its atmosphere contains water [http://lanl.arxiv.org/abs/0704.1114 (preprint)], although previous research [http://www.nature.com/nature/journal/v445/n7130/full/nature05636.html (L. J. Richardson et al. Nature 445, 892–895; 2007)] suggests that the atmosphere is composed mostly of silicate clouds.
{{PlanetboxOrbit begin}}
{{PlanetboxOrbit
| exoplanet = [[HD 209458 b|b]]
| mass = 0.69 ± 0.05
| period = 3.52474541 ± 0.00000025
| semimajor = 0.045
| eccentricity = 0.00
}}
{{PlanetboxOrbit end}}
==References==
* Tsevi Mazeh ''et al'', 2000, "The Spectroscopic Orbit of the Planetary Companion Transiting HD 209458", ''Astrophysical Journal'', vol. 532, pp. L55–L58.
==External links==
*[http://simbad.u-strasbg.fr/Simbad SIMBAD] [http://simbad.u-strasbg.fr/sim-id.pl?protocol=html&Ident=HD+209458 entry]
{{var-star-stub}}
[[Category:HD and HDE objects|209458]]
[[Category:HIP objects|108859]]
[[Category:Pegasus constellation]]
[[Category:Planetary transit variables]]
[[Category:Variable stars]]
[[Category:G-type main sequence stars]]
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