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Asymptotic giant branch – Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen; Galaxy color–magnitude diagram – Chart depicting the relationship between brightness and mass of large star systems; Hayashi track – Luminosity–temperature relationship in stars
minimum brightness [42] +1.33: star Alpha Centauri B: seen from Earth +1.86: planet Mars: seen from Earth minimum brightness [42] +1.98: star Polaris: seen from Earth mean brightness [49] +3.03: supernova SN 1987A: seen from Earth in the Large Magellanic Cloud (160,000 light-years away) +3 to +4: Faintest stars visible in an urban neighborhood ...
A star like Deneb, for example, has a luminosity around 200,000 L ⊙, a spectral type of A2, and an effective temperature around 8,500 K, meaning it has a radius around 203 R ☉ (1.41 × 10 11 m). For comparison, the red supergiant Betelgeuse has a luminosity around 100,000 L ⊙ , a spectral type of M2, and a temperature around 3,500 K ...
Early photometric measurements (made, for example, by using a light to project an artificial “star” into a telescope's field of view and adjusting it to match real stars in brightness) demonstrated that first magnitude stars are about 100 times brighter than sixth magnitude stars.
Once this distance is found, the distance away can be found via the arc subtended in the sky, giving a preliminary distance measurement. From this measurement and the apparent magnitudes of both stars, the luminosities can be found, and by using the mass–luminosity relationship, the masses of each star. These masses are used to re-calculate ...
The Greek astronomer Hipparchus established a numerical scale to describe the brightness of each star appearing in the sky. The brightest stars in the sky were assigned an apparent magnitude m = 1, and the dimmest stars visible to the naked eye are assigned m = 6. [7] The difference between them corresponds to a factor of 100 in brightness.
The spectral class of a star is a short code primarily summarizing the ionization state, giving an objective measure of the photosphere's temperature. Most stars are currently classified under the Morgan–Keenan (MK) system using the letters O, B, A, F, G, K, and M, a sequence from the hottest (O type) to the coolest (M type).
In astronomy, a period-luminosity relation is a relationship linking the luminosity of pulsating variable stars with their pulsation period. The best-known relation is the direct proportionality law holding for Classical Cepheid variables, sometimes called the Leavitt Law.