Space exploration began with the launch of Sputnik and Astrophysics was born as the application of physics to the phenomena observed by Astronomy, which etymologically means laws of the stars.
There are 2759 entries in this glossary.| Term | Definition |
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| Castor Alpha Geminorum; α Gem |
The second-brightest star in the constellation Gemini, after Pollux. Its magnitude as seen by the naked eye is 1.6, but this is the combined brightness of a multiple system with at least six components. There are two A stars of magnitudes 2.0 and 2.9 forming a close visual pair, each of which is a spectroscopic binary, and a more distant ninth magnitude red star, which is an eclipsing binary.
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