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Zodiac: Sagittarius
Nov 23 - Dec 21
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Castor A (α Geminorum)

Castor A (α Geminorum) is a white A-type dwarf star (A1V) in the constellation of Twins.
Castor can be found high up in the northern hemisphere. Together with his twin half-brother Castor B (α Geminorum) from the Greek and Roman mythology, Castor and Pollux are the main stars of the constellation Twins, marking the heads of the two twins.
Long known as a double star system, well visible in telescopes, Castor is in fact a system comprising six stars. All six stars are bound together by their gravity, where the two main components Castor A (α Geminorum) and Castor B (α Geminorum) revolve around each other in 420 years. Such complex multi star systems are very rare, which makes Castor truly amazing.
Right ascension
7h 34m 36s (113.65002°)
The magnitude (brightness) is measured on a logarithmic scale. Small numbers mean bright stars: A star with a brightness of 1 mag is 100 times brighter that an star with 6 mag.
2.11 mag
The distance is measured in light years (LY). A light year is the distance, that light travels within one year. 1 LJ is equal to about 5,878,630,000,000 miles.
5252 ly
Spectral type
Color index
Every star belongs to a constellation, and 12 of those constellations are part of the zodiac.
Gemini (Twins)
Artist impression of Castor A.
Image credit: NASA/SDO and the AIA, EVE, and HMI science teams
License: Public Domain
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This star is reserved and cannot be named.
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