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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| O Star |
A star of spectral type O. O stars have surface temperatures in the range 28,000-50,000 K and are bluish white in colour. Their spectra are characterized by lines of both neutral and ionized helium; emission lines are also commonly present. The four brightest O stars in the sky are Delta δ and Zeta ζ Orionis, the easternmost stars in Orion’s belt, and the southern stars Zeta ζ Puppis and Gamma2 γ2 Velorum.
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