Gamma Cephei

Starbox begin
name = Gamma CepheiStarbox observe
epoch = J2000.0
constell=Cepheus
ra = RA|23|39|20.8
dec = DEC|+77|37|56
appmag_v = 3.22Starbox character 2s
component1 = Gamma Cephei A
class1 = K1IVe
r-i1 =
v-r1 =
b-v1 = 1.03
u-b1 = 0.94
variable1 = Suspected
component2 = Gamma Cephei B
class2 = M4Vcite journal|url=http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?2007A%26A...462..777N&db_key=AST&nosetcookie=1|title=Direct detection of exoplanet host star companion γ Cep B and revised masses for both stars and the sub-stellar object|author=Neuhäuser, R.; Mugrauer, M.; Fukagawa, M.; Torres, G.; Schmidt, T.|year=2007|journal=Astronomy and Astrophysics|volume=462|issue=2|pages=777–780|doi=10.1051/0004-6361:20066581]
r-i2 =
v-r2 =
b-v2 =
u-b2 =
variable2 = Starbox astrometry
radial_v = 8.8
prop_mo_ra = -48.85
prop_mo_dec = 127.18
parallax = 72.69
p_error = 0.41
parallax_footnote =
absmag_v = 2.51Starbox orbit
primary = A
name = B
period = 67.5 ± 1.4
axis = 1.467 ± 0.046
axis_unitless = 20.18 ± 0.66 AU
eccentricity = 0.4112 ± 0.0063
periarg = 341.01 ± 0.40 [Neuhäuser et al. 2007 gives the value of the argument of periastron of the orbit of Gamma Cephei A around the barycentre. The argument of periastron of Gamma Cephei B's orbit differs by 180°.]
node = 18.04 ± 0.98
inclination = 119.3 ± 1.0
periastron = 1991.605 ± 0.031Starbox detail
source =
component1 = Gamma Cephei A
mass = 1.40 ± 0.12
radius = 4.7
luminosity = 10.6
temperature = 4800 ± 100
metal = 89-186%
rotation = 781 days
age = 6.6 × 10⁹cite journal | journal=The Astrophysical Journal | volume=654 | issue=2 | page=1095–1109 | url=http://www.journals.uchicago.edu/doi/abs/10.1086/509715 | format=abstract | title=The Planet Host Star γ Cephei: Physical Properties, the Binary Orbit, and the Mass of the Substellar Companion | author=Guillermo Torres | year=2007 | doi=10.1086/509715]
component2 = Gamma Cephei B
mass2 = 0.409 ± 0.018Starbox catalog
names = 35 Cep, Gl 903, HR 8974, BD +76°928, HD 222404, GCTP 5725.00, SAO 10818, FK5 893, HIP 116727. Starbox reference
Simbad=Gamma+Cephei

Gamma Cephei (γ Cep / γ Cephei), traditionally named Errai, Er Rai, and or Alrai, is a binary star system approximately 45 light-years away in the constellation of Cepheus. Gamma Cephei contains an apparent magnitude of 3.22. The visible part of the system is a stellar class K1III-IV orange subgiant star on its first ascent off the main sequence. It is currently thought to be 6.6 billion years old (based on Fe/H metallicity).

Gamma Cephei is the naked-eye star that will succeed Polaris as the Earth's northern pole star, due to the precession of the equinoxes. It will be closer to the northern celestial pole than Polaris around 3000 AD and will make its closest approach around 4000 AD. The "title" will pass to ι Cephei some time around 5200 AD.

Gamma Cephei's traditional name derives from the Arabic الراعي "ar-rā‘ī", meaning "the shepherd". Confusingly, the star β Ophiuchi is sometimes also called Alrai, but it is more commonly known as "Cebalrai" or "Kelb Alrai", meaning "shepherd's dog".

The star has a companion star with a mass approximately 0.409 times that of our Sun. Gamma Cephei B is of stellar mass and is assumed to be of similar age to its primary. It is probably a red dwarf of class M4, 6.2 degrees of magnitude fainter than the primary star in the K-band.

Planetary system

A planet orbiting Gamma Cephei A was tentatively identified by a Canadian team consisting of Bruce Campbell, Gordon Walker and Stephenson Yang in 1988. [cite journal | url=http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1988ApJ...331..902C | author=Campbell et al.| title=A search for substellar companions to solar-type stars | journal=The Astrophysical Journal | volume=331 |year=1988 | pages=902–921| doi=10.1086/166608 ] Its existence was also announced by Anthony Lawton and P Wright in 1989. This would have been the first confirmed extrasolar planet and its ostensible discovery was based on the same radial velocity technique later used successfully by others. However, the claim was retracted in 1992 because the quality of the data was not good enough to establish discovery. But in 2002, evidence of the planet was considerably strengthened by new measurements by Artie Hatzes and his collaborators at the McDonald Observatory. [cite journal | author=Hatzes "et al."| title =A Planetary Companion to Gamma Cephei A | journal=The Astrophysical Journal | year=2003 | volume=599 | issue=2 | pages=1383 – 1394 | url=http://www.journals.uchicago.edu/doi/full/10.1086/379281 | doi=10.1086/379281 ]

The secondary star B orbits A at only 9.5 times the semimajor axis of A's planet. This is the smallest ratio of planetary orbits in multiple systems. The orbits are probably coplanar.

PlanetboxOrbit
exoplanet = Ab
mass = >1.60 ± 0.13
period = 902.9 ± 3.5
semimajor = 2.044 ± 0.057
eccentricity = 0.115 ± 0.058

See also

* Iota Horologii
* Gliese 777

References

External links

* http://jumk.de/astronomie/exoplanets/errai.shtml
* [http://mcdonaldobservatory.org/news/releases/2002/1009.html McDonald Observatory: Planet Search finds first planet orbiting close-in binary star]
* [http://austral.as.utexas.edu/planets/gamcep/gamcep.html A Planetary Companion to the Binary Star Gamma Cephei]
* [http://www.solstation.com/stars2/errai2.htm SolStation: Errai 2]
* [http://exoplanet.eu/star.php?st=Gamma+Cephei Extrasolar Planets Encyclopaedia: Gamma Cephei]
* [http://www.extrasolar.net/startour.asp?StarCatId=normal&StarId=196 Extrasolar Visions: Gamma Cephei A] + [http://www.extrasolar.net/planettour.asp?StarCatId=normal&PlanetId=235 Gamma Cephei Ab] + [http://www.extrasolar.net/startour.asp?StarCatId=normal&StarId=230 Gamma cephei B]