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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.
K-type main-sequence stars are about three to four times as abundant as G-type main-sequence stars, making planet searches easier. [17] K-type stars emit less total ultraviolet and other ionizing radiation than G-type stars like the Sun (which can damage DNA and thus hamper the emergence of nucleic acid based life). In fact, many peak in the red.
[c] [11] Some of the most massive stars lie within this spectral class. O-type stars frequently have complicated surroundings that make measurement of their spectra difficult. O-type spectra formerly were defined by the ratio of the strength of the He II λ4541 relative to that of He I λ4471, where λ is the radiation wavelength. Spectral type ...
Beta Cassiopeiae (β Cassiopeiae, abbreviated Beta Cas or β Cas), officially named Caph / ˈ k æ f /, [12] [13] is a Delta Scuti variable star in the constellation of Cassiopeia. It is a giant star belonging to the spectral class F2. The white star of second magnitude (+2.28 mag, variable) has an absolute magnitude of +1.3 mag.
Beta Lyrae Aa is a semidetached binary system made up of a stellar class B6-8 primary star and a secondary that is probably also a B-type star. The fainter, less massive star in the system was once the more massive member of the pair, which caused it to evolve away from the main sequence first and become a giant star.
The radial velocity variations of the stars can be measured and the pair have a somewhat eccentric orbit of 51.4 days. [3] The secondary is a main-sequence star slightly cooler than the primary, with an A1 spectral class. [3] The secondary star was detected in high spatial resolution observations using the Navy Precision Optical Interferometer.
The primary is a yellow giant that has cooled and expanded to 10.4 times the diameter of the Sun. [36] Of spectral class G8IV, it is around 121 light-years away, [37] while the secondary is a yellow main sequence star of spectral type G0V. [38] The two are thought to take 120,000 years to orbit each other. [36]
As of March 2017, the star is known to have at least 5 planets, with two of them (HD 219134 b and c) known to be transiting, rocky super-Earths. [17] [18] While a 2016 study suggested that the radial velocity signal corresponding to planet f might be caused by stellar activity, [16] it has been confirmed by subsequent studies in 2017 [17] and ...