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This image is a derivative work of the following images: File:Empty_Star.svg licensed with PD-self . 2006-11-09T10:00:31Z Kbolino 64x64 (2599 Bytes) For use with star ratings: a single empty star
Stars in the night sky. The first star catalogue in Greek astronomy was created by Aristillus in approximately 300 BC, with the help of Timocharis. [10] The star catalog of Hipparchus (2nd century BC) included 1,020 stars, and was used to assemble Ptolemy's star catalogue. [11] Hipparchus is known for the discovery of the first recorded nova ...
The star contains starspots on its surface ζ And Aa 2.502 ± 0.008: 15.0 ± 0.8 (polar) 189 ± 3: CFHT [9] [10] 1996: First direct imaging of starspots on a star outside the Solar System. R Dor: 57 ± 5: 370 ± 50: 204 ± 9: New Technology Telescope [11] 1993: 2nd largest known star by apparent diameter in Earth's sky, after the Sun. Mira ο ...
The phrase "fixed star" is technically incorrect, but nonetheless it is used in an historical context, and in classical mechanics. When used as a visual reference for observations, they usually are called background stars or simply distant stars, still retaining the intuitive meaning of they being "fixed" in some practical sense.
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The radiation is remarkably uniform across the sky, very unlike the almost point-like structure of stars or clumps of stars in galaxies. [6] The radiation is isotropic to roughly one part in 25,000: the root mean square variations are just over 100 μK, [ 7 ] after subtracting a dipole anisotropy from the Doppler shift of the background radiation.
The Sun is composed primarily of the chemical elements hydrogen and helium; they account for 74.9% and 23.8%, respectively, of the mass of the Sun in the photosphere.All heavier elements, colloquially called metals in stellar astronomy, account for less than 2% of the mass, with oxygen (roughly 1% of the Sun's mass), carbon (0.3%), neon (0.2%), and iron (0.2%) being the most abundant.