Structured Lists Directory

Overview

Stellar Spectral Classification

The Stellar Spectral Classification is a classification system developed by Annie Jump Cannon and colleagues at Harvard College Observatory between 1918 and 1924. It categorizes stars into ten types (O, B, A, F, G, K, M, L, T, Y) based on surface temperature, systematically organizing everything from the hottest blue giants to the coolest brown dwarfs. This classification was formally adopted by the precursor to the International Astronomical Union in 1922 and remains the standard classification system used worldwide in astronomy today.

astronomy stars spectral classification Harvard classification surface temperature brown dwarfs
code slug name description abundance_percent color example_stars lifespan mass_solar_max mass_solar_min mass_solar_typical temperature_max_kelvin temperature_min_kelvin temperature_note temperature_typical_kelvin mass_jupiter_max mass_jupiter_min mass_jupiter_typical object_type
O o-type O-type Star The hottest and most massive blue giant stars. <1 Blue ["Zeta Ophiuchi","Lambda Orionis","Theta1 Orionis C"] 5-6 million years 150 16 30 50000 28000 Some subdwarfs can exceed 100,000K
B b-type B-type Star Hot blue-white massive stars. 0.13 Blue-white ["Rigel","Spica","Regulus"] ~300 million years 16 2.1 7 30000 10000 15000
A a-type A-type Star White stars with the strongest hydrogen lines. 0.625 White ["Sirius A","Vega","Altair","Fomalhaut"] 1-2 billion years 2.1 1.4 1.7 10000 7400 8500
F f-type F-type Star Yellow-white stars with intermediate temperature. 3 Yellow-white ["Procyon A","Polaris Aa","Canopus"] 4-8 billion years 1.4 1 1.2 7500 6000 6700
G g-type G-type Star (Yellow Dwarf) Yellow main-sequence stars like our Sun. 7.5 Yellow ["Sun","Alpha Centauri A","Tau Ceti","51 Pegasi"] ~10 billion years (for solar mass) 1.15 0.8 1 6000 5200 5778
K k-type K-type Star (Orange Dwarf) Orange main-sequence stars cooler than the Sun. 12 Orange ["Epsilon Eridani","Alpha Centauri B","61 Cygni A"] 17-70 billion years 0.8 0.5 0.65 5200 3900 4500
M m-type M-type Star (Red Dwarf) The most common and longest-lived red main-sequence stars. 75 Red ["Proxima Centauri","Barnard's Star","TRAPPIST-1","Wolf 359"] 1-10 trillion years 0.5 0.08 0.3 3900 2400 3200
L l-type L-type Dwarf Cool brown dwarfs with water and metal hydride absorption. Dark red ["2MASS J0523-1403","DENIS-P J1228.2-1547"] 2500 1300 1900 65 13 30 Brown dwarf or cool star
T t-type T-type Dwarf Cool brown dwarfs with methane absorption bands. Magenta/Black ["Gliese 570 D","WISE J0350-5658","2MASS J0559-1404"] 1500 600 1000 80 13 50 Brown dwarf
Y y-type Y-type Dwarf The coldest brown dwarfs with ammonia absorption features. Black (detectable only in infrared) ["WISE J0855-0714","WISE J1828+2650","WISE J1738+2732"] 600 200 400 80 13 50 Brown dwarf

The Harvard spectral classification system that categorizes stars based on their surface temperature.