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[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 ...
The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts ...
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.
HD 141569 is an isolated [5] Herbig Ae/Be star [6] of spectral class A2Ve [7] approximately 364 light-years away in the constellation of Libra. The primary star has two red dwarf companions (orbiting each other) at about nine arcseconds. In 1999, a protoplanetary disk was discovered around the star.
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.
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 ...
It is the central star of NGC 2392 Planetary Nebula. WR 25 (HD 93162) 6,500: 2: O2.5If*/WN6 + OB: 8.80: Pismis 24-1 (HD 319718) 6,500: 2: O3.5If*+O4III(f+) HD 151804 (V973 Scorpii) 7,000: 1: O8 Iaf: 5.22 - 5.28: HD 138403: 7175.44: 1: O8(f)ep: It is the central star of Hen 2-131 Planetary Nebula. Cygnus X-1: 7,300 ± 200: 2: O9.7Iab: 8.95 ...
The term subgiant was first used in 1930 for class G and early K stars with absolute magnitudes between +2.5 and +4. These were noted as being part of a continuum of stars between obvious main-sequence stars such as the Sun and obvious giant stars such as Aldebaran, although less numerous than either the main sequence or the giant stars.