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Spectra of a hypothetical M5V star. Class M stars are by far the most common. About 76% of the main-sequence stars in the solar neighborhood are class M stars. [c] [f] [11] However, class M main-sequence stars have such low luminosities that none are bright enough to be seen with the unaided eye, unless under exceptional conditions.
The first list shows a few of the known stars with an estimated luminosity of 1 million L ☉ or greater, including the stars in open cluster, OB association and H II region. The majority of stars thought to be more than 1 million L ☉ are shown, but the list is incomplete. The second list gives some notable stars for the purpose of comparison.
A B-type main-sequence star (B V) is a main-sequence (hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. [1] B-type stars are extremely luminous and blue.
A hypergiant (luminosity class 0 or Ia +) is a very rare type of star that has an extremely high luminosity, mass, size and mass loss because of its extreme stellar winds.The term hypergiant is defined as luminosity class 0 (zero) in the MKK system.
An artist's impression of Sirius A and Sirius B, a binary star system. Sirius A, an A-type main-sequence star, is the larger of the two. An A-type main-sequence star (A V) or A dwarf star is a main-sequence (hydrogen burning) star of spectral type A and luminosity class V (five). These stars have spectra defined by strong hydrogen Balmer ...
An F-type main-sequence star (F V) is a main-sequence, hydrogen-fusing star of spectral type F and luminosity class V. These stars have from 1.0 to 1.4 times the mass of the Sun and surface temperatures between 6,000 and 7,600 K. [2] Tables VII and VIII. This temperature range gives the F-type stars a whitish hue when observed by the atmosphere.
Blue and white supergiants are high luminosity stars somewhat cooler than the most luminous main sequence stars. 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).
The luminosity class ranged from I to V, in order of decreasing luminosity. Stars of luminosity class V belonged to the main sequence. [7] In April 2018, astronomers reported the detection of the most distant "ordinary" (i.e., main sequence) star, named Icarus (formally, MACS J1149 Lensed Star 1), at 9 billion light-years away from Earth. [8] [9]