Thuban

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Double star
α Draconis
AladinLite
Observation
dates equinox :  J2000.0 , epoch : J2000.0
Constellation Dragon
Right ascension 14 h 04 m 23.35 s
declination + 64 ° 22 ′ 33.1 ″
Apparent brightness 3.67 likes
Typing
B − V color index −0.05 
U − B color index −0.08 
R − I index −0.07 
Spectral class A0 III
Astrometry
parallax (10.76 ± 0.17)  mas
distance (303 ± 5)  ly
(92.9 ± 1.5)  pc  
Visual absolute brightness M vis −1.17 mag
Proper movement 
Rec. Share: (−56.34 ± 0.15)  mas / a
Dec. portion: (17.21 ± 0.15)  mas / a
Physical Properties
Other names
and catalog entries
Bayer name α Draconis
Flamsteed name 11 Draconis
Bonn survey BD + 65 ° 978
Bright Star Catalog HR 5291 [1]
Henry Draper Catalog HD 123299 [2]
Hipparcos catalog HIP 68756 [3]
SAO catalog SAO 16273 [4]
Tycho catalog TYC 4174-1262-1 [5]
Other names FK5 521
annotation
  1. ↑ roughly estimated from apparent brightness and distance

Thuban ( Arabic ثعبان, DMG ṯuʿbān  ' snake ') is the proper name of the star α Draconis (Alpha Draconis) in the constellation Dragon . Thuban belongs to the spectral class A0 and has an apparent magnitude of 3.1 mag. Thuban is about 300 light years from Earth.

Around 2800 BC Thuban served as a pole star to determine the northern celestial pole. Since the earth's axis is not completely stable in space, but performs a slow circular motion ( precession ), the position of the celestial poles shifts slowly . As a result, other stars can take over the function of the pole star over time. The identification of Thuban as the main star (i.e. alpha ) of the dragon goes back to this earlier special meaning of the star .

Individual evidence

  1. ↑ a b c Hipparcos catalog (ESA 1997)
  2. ↑ a b c Bright Star Catalog
  3. ↑ a b c Hipparcos, the New Reduction (van Leeuwen, 2007)
  4. ↑ dtv-Atlas zur Astronomie, Munich 1973