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In doing so, he also developed the brightness scale still in use today. [1] Hipparchus compiled a catalogue with at least 850 stars and their positions. [2] Hipparchus's successor, Ptolemy, included a catalogue of 1,022 stars in his work the Almagest, giving their location, coordinates, and brightness. [3]
Apparent magnitude (m) is a measure of the brightness of a star, astronomical object or other celestial objects like artificial satellites. Its value depends on its intrinsic luminosity , its distance, and any extinction of the object's light caused by interstellar dust along the line of sight to the observer.
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This is a list of stars arranged by their apparent magnitude – their brightness as observed from Earth. It includes all stars brighter than magnitude +2.50 in visible light, measured using a V-band filter in the UBV photometric system.
Consequently, a magnitude 1 star is about 2.5 times brighter than a magnitude 2 star, about 2.5 2 times brighter than a magnitude 3 star, about 2.5 3 times brighter than a magnitude 4 star, and so on. This is the modern magnitude system, which measures the brightness, not the apparent size, of stars.
Photometry is also used in the observation of variable stars, [4] by various techniques such as, differential photometry that simultaneously measures the brightness of a target object and nearby stars in the starfield [5] or relative photometry by comparing the brightness of the target object to stars with known fixed magnitudes. [6]
Galaxy color–magnitude diagram – Chart depicting the relationship between brightness and mass of large star systems Hayashi track – Luminosity–temperature relationship in stars Henyey track – path taken by pre-main-sequence stars in the Hertzsprung–Russell diagram Pages displaying wikidata descriptions as a fallback
(The S 10 unit is defined as the surface brightness of a star whose V-magnitude is 10 and whose light is smeared over one square degree, or 27.78 mag arcsec −2.) The total sky brightness in zenith is therefore ~220 S 10 or 21.9 mag/arcsec² in the V-band. Note that the contributions from Airglow and Zodiacal light vary with the time of year ...