(Alpha Geminorum C) is the Bayer Classification for the star. The Bayer Classification was created by Johann Bayer in the early nineteenth century. The brightest star in the constellation is normally given the Alpha designation although there are exceptions such as Pollux which is Beta Geminorum.
Castor C has alternative name(s) :- YY Geminorum.
More details on objects' alternative names can be found at Star Names .
The location of the main sequence 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 object is compared to the celestial equator and is expressed in degrees. For Castor C, the location is 07h 34m 37.584 and +31 ° 53` 17.81 .
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 -96.00 milliarcseconds/year towards the north and -207.60 milliarcseconds/year east if we saw them in the horizon.
The Radial Velocity, that is the speed at which the star is moving away/towards the Sun is 2.50 km/s . When the value is negative then the star and the Sun are getting closer to one another, likewise, a positive number means that two stars are moving away. Its nothing to fear as the stars are so far apart, they won't collide in our life-time, if ever.
Castor C has a spectral type of M0.5VeFe-2 C. This means the star is a red main sequence star.
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.
The star is a rotating BY Draconis variable type which means that its size changes over time. The Variable Type is usually named after the first star of that type to be spotted.
|Primary / Proper / Traditional Name||Castor C|
|Alternative Names||Alpha Geminorum C, YY Geminorum|
|Spectral Type||M0.5VeFe-2 C|
|Constellation's Main Star||No|
|Multiple Star System||Yes|
|Star Type||Main Sequence Dwarf Star|
|Right Ascension (R.A.)||07h 34m 37.584|
|Declination (Dec.)||+31 ° 53` 17.81|
|Proper Motion Dec.||-96.00 milliarcseconds/year|
|Proper Motion RA.||-207.60 milliarcseconds/year|
|Radial Velocity||2.50 km/s|
|Associated / Clustered Stars||Castor|
|Variable Star Class||Rotating|
|Variable Star Type||BY Draconis|
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