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Of the main-sequence star types, stars more massive than 1.5 times that of the Sun (spectral types O, B, and A) age too quickly for advanced life to develop (using Earth as a guideline). On the other extreme, dwarfs of less than half the mass of the Sun (spectral type M) are likely to tidally lock planets within their habitable zone, along with ...
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 ...
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.
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 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).
A spectral atlas can be a very high-quality spectrum of a key reference object, often made with very high spectral resolution, generally presented in large-format graphical form as a line chart (but normally strictly without markers at specific data points) of intensity or relative intensity (which for a star whose spectrum is dominated by absorption lines runs from zero to a normalized ...
Alpha Sextantis is the brightest star in the constellation and the only star above the fifth magnitude with an apparent magnitude of 4.49. It is an ageing A-type star of spectral class A0 III [7] located 280 ± 20 light-years away [8] from the Solar System. At the age of 385 million years, [9] it is exhausting hydrogen at its core and leaving ...
Class II objects have circumstellar disks and correspond roughly to classical T Tauri stars, while Class III stars have lost their disks and correspond approximately to weak-line T Tauri stars. An intermediate stage where disks can only be detected at longer wavelengths (e.g., at 24 μ m {\displaystyle 24{\mu }m} ) are known as transition-disk ...