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The Yerkes spectral classification, also called the MK, or Morgan-Keenan (alternatively referred to as the MKK, or Morgan-Keenan-Kellman) [18] [19] system from the authors' initials, is a system of stellar spectral classification introduced in 1943 by William Wilson Morgan, Philip C. Keenan, and Edith Kellman from Yerkes Observatory. [20]
Below there are lists the nearest stars separated by spectral type. The scope of the list is still restricted to the main sequence spectral types: M, K, F, G, A, B and O. It may be later expanded to other types, such as S, D or C. The Alpha Centauri star system is the closest star system to the Sun.
The Sun, a spectral class G2V main-sequence star; The inner Solar System and the terrestrial planets. 2021 PH27; Mercury. Mercury-crossing minor planets; Venus. Venus-crossing minor planets. 524522 Zoozve, Venus' quasi-satellite; Earth. Moon; Near-Earth asteroids (including 99942 Apophis) Earth trojan (2010 TK 7) Earth-crosser asteroids. Earth ...
The classes of the stars and brown dwarfs are shown in the color of their spectral types (these colors are derived from conventional names for the spectral types and do not necessarily represent the star's observed color).
The spectral type is not a numerical quantity, but the sequence of spectral types is a monotonic series that reflects the stellar surface temperature. Modern observational versions of the chart replace spectral type by a color index (in diagrams made in the middle of the 20th Century, most often the B-V color) of the stars.
Comparison of main sequence stars of each spectral class. By treating the star as an idealized energy radiator known as a black body, the luminosity L and radius R can be related to the effective temperature T eff by the Stefan–Boltzmann law: = where σ is the Stefan–Boltzmann constant. As the position of a star on the HR diagram shows its ...
A black hole (artist concept); Vela Pulsar, a rotating neutron star; M80, a globular cluster, and the Pleiades, an open star cluster; The Whirlpool Galaxy and Abell 2744, a galaxy cluster; Superclusters, galactic filaments and voids
A-type star In the Harvard spectral classification system, a class of main-sequence star having spectra dominated by Balmer absorption lines of hydrogen. Stars of spectral class A are typically blue-white or white in color, measure between 1.4 and 2.1 times the mass of the Sun, and have surface temperatures of 7,600–10,000 kelvin.