Castor

Castor also known as Alpha Geminorum is a multiple star system in the constellation Gemini its composed of six separate stars in three binary systems although in 1718 was only assumed to be two stars but from earth only looks like one unless viewed with a high-quality telescope and is usually counted as one they are the second brightest star in Gemini with Pollux being the brightest and one of the twenty-three brightest stars in the sky they are about fifty-one light years from earth the two main stars are very large blue main sequence stars that are more massive than our sun the rest are red dwarf stars half the mass of the sun they were the first true physical binary to be discovered the brightest binary castor is made up of castor Aa and Castor Ab that orbit each other about every nine earth days Castor Aa is the second largest star in Castor its surface also reaches eighteen thousand fifty five degrees Fahrenheit which is hotter than our sun Castor B is made up of Castor Ba and Bb which orbits each other every two earth days Ba is the largest star in Castor Ba is cooler than Aa by three thousand but is still hotter than the sun Castor C is the faintest and is made up of Castor Ca and Castor Cb that orbit each other every nineteen and a half earth hours they are both cooler and fainter than the sun though Castor C is brighter than Castor A and Castor B on X-Ray

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