Castor - α Geminorum (alpha Geminorum)
Castor, also designated as α Geminorum (alpha Geminorum), is a variable and multiple main-sequence star of spectral class A1 in the constellation of Gemini.
Castor visual magnitude is 1.98, making it the 46th brightest star in the sky. Because of its brightness, Castor is clearly visible to the naked eye when observed from locations with dark skies, and should be also quite easily visible from light polluted areas.
Celestial Coordinates
Apparent
J2000
Galactic Coordinates
Finder Chart
Simplified finder chart for Castor - α Geminorum (alpha Geminorum).
Magnitude, Color, Spectral Class
The red dot in the diagram below shows where Castor is situated in the Hertzsprung–Russell diagram.
Star System Properties
Castor is a visual double star which can be observed with the help of medium or large telescopes. The table below shows key information about the Castor double sysyem:
Distance, Radial Speed, Proper Motion
Castor is distant 51.53 light years from the Sun and it is moving far from the Sun at the speed of 6 kilometers per second.
Alternative Designations
Visibility from Your Location
Today's Castor - α Geminorum (alpha Geminorum) rise, transit and set times from Greenwich, UK are the following (all times relative to the local timezone Europe/London):