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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| Umbra 2 |
The dark central region of a sunspot, where the magnetic field is vertical and typically has a strength a few thousand times that at the surface of the Earth. The temperature is about 3,500 K, compared with 6,000 K for the surrounding photosphere.
See also: penumbra.
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