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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| Celestial Equator |
The great circle on the celestial sphere marking the boundary between the northern and southern hemispheres, and acting as the zero-mark for declination. It is the projection into space of the Earth’s equatorial plane.
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