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Castor B, Alpha Geminorum B, HD60178, HR2890

Castor B (Alpha Geminorum B) Location in Gemini

Castor B (Alpha Geminorum B) is a subgiant star that can be located in the constellation of Gemini. The description is based on the spectral class. The star can be seen with the naked eye, that is, you don't need a telescope/binoculars to see it.

Castor B's Alternative Names

(Alpha Geminorum B) is the Bayer Classification for the star. The Id of the star in the Yale Bright Star Catalogue is HR2890. The Id of the star in the Henry Draper catalogue is HD60178.

More details on star alternative names can be found at Star Names .

Location of Castor B

The location of the star in the night sky is determined by the Right Ascension (R.A.) and Declination (Dec.), these are equivalent to the Longitude and Latitude on the Earth. The Right Ascension is how far expressed in time (hh:mm:ss) the star is along the celestial equator. If the R.A. is positive then its eastwards. The Declination is how far north or south the star is compared to the celestial equator and is expressed in degrees. For Castor B, the location is 07h 34m 36.10 and +31 ° 53` 18.57 .

Proper Motion of Castor B

All stars like planets orbit round a central spot, in the case of planets, its the central star such as the Sun. In the case of a star, its the galactic centre. The constellations that we see today will be different than they were 50,000 years ago or 50,000 years from now. Proper Motion details the movements of these stars and are measured in milliarcseconds. The star is moving -148.20 miliarcseconds/year towards the north and -206.30 miliarcseconds/year east if we saw them in the horizon. The Radial Velocity, that is the speed at which the star is moving away/towards us is -1.20000 km/s .

Physical Properties of Castor B

Castor B has a spectral type of kA0hA2:mA1IVs B.

Castor B Apparent and Absolute Magnitudes

Castor B has an apparent magnitude of 2.97 which is how bright we see the star from Earth. Apparent Magnitude is also known as Visual Magnitude. Magnitude, whether it be apparent/visual or absolute magnitude is measured by a number, the smaller the number, the brighter the Star is. Our own Sun is the brightest star and therefore has the lowest of all magnitudes, -26.74. A faint star will have a high number.

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Castor B Facts

Visual Facts


Primary / Proper / Traditional NameCastor B
Alternative NamesAlpha Geminorum B, HD 60178, HR 2890
Spectral TypekA0hA2:mA1IVs B
Multiple Star SystemYes
Star TypeSubgiant Star
GalaxyMilky Way
ConstellationGemini
Visual / Apparent Magnitude2.97
Naked Eye VisibleYes - Magnitudes
Right Ascension (R.A.)07h 34m 36.10
Declination (Dec.)+31 ° 53` 18.57
Proper Motion Dec.-148.20 milliarcseconds/year
Proper Motion RA.-206.30 milliarcseconds/year
Radial Velocity-1.20 km/s
Associated / Clustered StarsCastor
Castor C

Companions (Multi-Star and Exoplanets) Facts


Exoplanet CountNone/Unaware

Estimated Facts


Sources and Links


Sourcehttp://simbad.u-strasbg.fr/simbad/sim-id?Ident=Castor%20B

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