Types of Astronomical Spectral Class Star
Spectral Class↕ | Surface Temperature↕ | Color↕ | Example Star↕ | Known For↕ |
|---|---|---|---|---|
O-Type | 30,000-50,000+ K | Blue | Alnitak (Orion's Belt) | Hottest and most massive stars, extremely rare (<0.00003% of all stars), burn through hydrogen in millions of years, die as supernovae |
B-Type | 10,000-30,000 K | Blue-white | Rigel, Spica | Hot luminous stars, Rigel 120,000x Sun's luminosity, form OB associations, many in Orion, relatively short-lived |
A-Type | 7,500-10,000 K | White | Sirius, Vega | Sirius is brightest star in night sky, Vega was first star photographed (1850), strong hydrogen absorption lines |
F-Type | 6,000-7,500 K | Yellow-white | Canopus, Procyon | Slightly hotter than Sun, Canopus is second brightest star, often used for spacecraft navigation, F-type dwarfs may host habitable planets |
G-Type (Solar type) | 5,200-6,000 K | Yellow | Sun, Alpha Centauri A | Our Sun is a G2V star, 'Goldilocks' temperature for life, about 7.5% of all stars, yellow dwarf misnomer (actually white) |
K-Type | 3,700-5,200 K | Orange | Arcturus, Alpha Centauri B | Considered best candidates for habitable planets (stable, long-lived, less UV than G-type), Arcturus is 4th brightest star |
M-Type (Red Dwarf) | 2,400-3,700 K | Red | Proxima Centauri, Barnard's Star | Most common stars in universe (~73% of all stars), live for trillions of years, Proxima hosts nearest known exoplanet, too dim to see with naked eye |
L-Type (Brown Dwarf) | 1,300-2,400 K | Dark red / magenta | 2MASS J1507-1627 | Failed stars too small for hydrogen fusion, bridge between stars and planets, lithium absorption lines, discovered 1990s |
T-Type (Cool Brown Dwarf) | 500-1,300 K | Magenta / invisible | Gliese 229B | Methane-dominated atmospheres like Jupiter, cool enough for weather systems and clouds, some may rain iron droplets |
Y-Type (Ultra-cool) | <500 K | Invisible (infrared only) | WISE 0855-0714 | Coldest known 'stars', some cooler than room temperature, water ice clouds possible, discovered by WISE space telescope |
Wolf-Rayet (WR) | 30,000-200,000 K | Blue | WR 142, Gamma Velorum | Massive dying stars blowing off their outer layers in fierce stellar winds, exposed helium cores, precursors to supernovae/black holes |
Carbon Star (C-Type) | 2,000-3,500 K | Deep red | R Leporis (Hind's Crimson Star) | Red giants with excess carbon, appear strikingly red, carbon soot in atmosphere, named 'crimson stars' by Victorian astronomers |
S-Type | 3,000-3,500 K | Red-orange | Chi Cygni | Transitional between M and C types, contain zirconium oxide, intermediate carbon content, often long-period variable stars |
White Dwarf (D) | 4,000-150,000 K | White to blue | Sirius B | Dead stellar cores, Earth-sized but Sun-mass, teaspoon weighs 5 tons, will become our Sun's fate in 5 billion years |
Subdwarf B (sdB) | 20,000-40,000 K | Blue | HD 188112 | Stripped red giant cores burning helium, lost hydrogen envelope (possibly to companion star), key to understanding stellar evolution |
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