Gamma Cephei

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Double star
γ Cephei (Errai)
Observation
dates equinox :  J2000.0 , epoch : J2000.0
AladinLite
Constellation Cepheus
Right ascension 23 h 39 m 20.8 s
declination + 77 ° 37 ′ 56 ″
Apparent brightness  3.2 mag
Known exoplanets

1

Astrometry
Radial velocity (−44.4 ± 0.2) km / s
parallax (70.91 ± 0.40) mas
distance  (46.00 ± 0.26) Ly
((14.10 ± 0.08) pc )
Proper movement :
Rec. Share: −48 mas / a
Dec. portion: +127 mas / a
orbit 
period (67.5 ± 1.4) a
Major semi-axis 1 ", 47 ± 0", 05
eccentricity 0.411 ± 0.006
Orbit inclination 119 °, 3 ± 1 °, 0
Argument of the node 18 °, 0 ± 1 °, 0
Epoch of the periastron 1991.61 ± 0.03
Argument of the periapsis 161 °, 0 ± 0 °, 4
Individual data
Names A; B.
Observation data:
Apparent brightness A. 3.22 mag
B.
Typing:
Spectral class A. K1 IV
B − V color index A. +1.03
U − B color index A. +0.94
Physical Properties:
Absolute vis.
Brightness M vis 		A. +2.5 mag
B.
Dimensions A. (1.40 ± 0.12) M ☉
B. (0.409 ± 0.018) M ☉
Other names
and catalog entries
Bayer name γ Cephei
Flamsteed name 35 Cephei
Bonn survey BD + 76 ° 928
Bright Star Catalog HR 8974 [1]
Henry Draper Catalog HD 222404 [2]
SAO catalog SAO 10818 [3]
Tycho catalog TYC 4606-3584-1 [4]
Hipparcos catalog HIP 116727 [5]
Further designations: Gliese 903 • FK5  893

γ Cephei (Gamma Cephei ; proper name Errai or Alrai from Arabic الراعي, DMG ar-rāʿī  , the shepherd / shepherd ') is a star of the spectral class K1 IV with an apparent magnitude of 3.2 mag. The distance to earth is about 46 light years .

γ Cephei is a double star , consisting of a subgiant and a red dwarf . The red dwarf moves on an orbit with a major semi-axis of 20  AU and an eccentricity of 0.41 around the subgiant. One cycle takes around 70 years.

Due to the precession of the earth's axis, γ Cephei will be the closest star visible to the naked eye at the north celestial pole. Due to the shift of the earth's axis, the star apparently moves in the direction of the celestial north pole and from the year 3000 will have a smaller distance to the celestial north pole than the pole star . Its closest convergence will take place around the year 4000 before it will be followed by Cephei in the role of Pole Star around the year 5200 .

In 1989 the discovery of an exoplanet around γ Cephei was announced by Anthony Lawton and P. Wright . That would have been the first discovery of such a planet, based on the measurement of the radial velocity of the system, which later successfully identified planets in other stars. However, the discovery was revoked in 1992. Later, in 2002, new measurements confirmed the existence of the planet γ Cephei Ab , which accordingly orbits the star once in about 900 days and has at least 1.6 times the mass of Jupiter.

It is speculated that conditions could prevail in the system which enable the development of life. On September 30, 2006, the Franco-German TV culture channel Arte transmitted the television program CosmicConnexion, which was also broadcast in Europe, in the direction of γ Cephei via the parabolic antenna of the space center CNES , in the hope of reaching a civilization that happened to live there. In the 160-minute broadcast, the hoped-for aliens are shown people and their everyday lives. The shipment will reach γ Cephei in 2051. A possible response from the aliens would not reach Earth until 2096 at the earliest. Because of the great distance, broadcast and response are each 45 years on the road.

Individual evidence

  1. ↑ a b Hipparcos catalog (ESA 1997)
  2. ↑ Pulkovo radial velocities for 35493 HIP stars
  3. ^ Hipparcos, the New Reduction (van Leeuwen, 2007)
  4. ↑ a b Bright Star Catalog

literature

  • Neuhäuser et al .: Direct detection of exoplanet host star companion γ Cep B and revised masses for both stars and the sub-stellar object. bibcode : 2007A & A ... 462..777N