Structured Lists Directory

TOML

Stellar Spectral Classification - TOML

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 
[[items]]
code = "O"
slug = "o-type"
name = "O-type Star"
description = "The hottest and most massive blue giant stars."
abundance_percent = "<1"
color = "Blue"
example_stars = "[\"Zeta Ophiuchi\",\"Lambda Orionis\",\"Theta1 Orionis C\"]"
lifespan = "5-6 million years"
mass_solar_max = 150
mass_solar_min = 16
mass_solar_typical = 30
temperature_max_kelvin = 50000
temperature_min_kelvin = 28000
temperature_note = "Some subdwarfs can exceed 100,000K"
temperature_typical_kelvin = ""
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "B"
slug = "b-type"
name = "B-type Star"
description = "Hot blue-white massive stars."
abundance_percent = "0.13"
color = "Blue-white"
example_stars = "[\"Rigel\",\"Spica\",\"Regulus\"]"
lifespan = "~300 million years"
mass_solar_max = 16
mass_solar_min = 2.1
mass_solar_typical = 7
temperature_max_kelvin = 30000
temperature_min_kelvin = 10000
temperature_note = ""
temperature_typical_kelvin = 15000
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "A"
slug = "a-type"
name = "A-type Star"
description = "White stars with the strongest hydrogen lines."
abundance_percent = "0.625"
color = "White"
example_stars = "[\"Sirius A\",\"Vega\",\"Altair\",\"Fomalhaut\"]"
lifespan = "1-2 billion years"
mass_solar_max = 2.1
mass_solar_min = 1.4
mass_solar_typical = 1.7
temperature_max_kelvin = 10000
temperature_min_kelvin = 7400
temperature_note = ""
temperature_typical_kelvin = 8500
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "F"
slug = "f-type"
name = "F-type Star"
description = "Yellow-white stars with intermediate temperature."
abundance_percent = "3"
color = "Yellow-white"
example_stars = "[\"Procyon A\",\"Polaris Aa\",\"Canopus\"]"
lifespan = "4-8 billion years"
mass_solar_max = 1.4
mass_solar_min = 1
mass_solar_typical = 1.2
temperature_max_kelvin = 7500
temperature_min_kelvin = 6000
temperature_note = ""
temperature_typical_kelvin = 6700
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "G"
slug = "g-type"
name = "G-type Star (Yellow Dwarf)"
description = "Yellow main-sequence stars like our Sun."
abundance_percent = "7.5"
color = "Yellow"
example_stars = "[\"Sun\",\"Alpha Centauri A\",\"Tau Ceti\",\"51 Pegasi\"]"
lifespan = "~10 billion years (for solar mass)"
mass_solar_max = 1.15
mass_solar_min = 0.8
mass_solar_typical = 1
temperature_max_kelvin = 6000
temperature_min_kelvin = 5200
temperature_note = ""
temperature_typical_kelvin = 5778
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "K"
slug = "k-type"
name = "K-type Star (Orange Dwarf)"
description = "Orange main-sequence stars cooler than the Sun."
abundance_percent = "12"
color = "Orange"
example_stars = "[\"Epsilon Eridani\",\"Alpha Centauri B\",\"61 Cygni A\"]"
lifespan = "17-70 billion years"
mass_solar_max = 0.8
mass_solar_min = 0.5
mass_solar_typical = 0.65
temperature_max_kelvin = 5200
temperature_min_kelvin = 3900
temperature_note = ""
temperature_typical_kelvin = 4500
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "M"
slug = "m-type"
name = "M-type Star (Red Dwarf)"
description = "The most common and longest-lived red main-sequence stars."
abundance_percent = "75"
color = "Red"
example_stars = "[\"Proxima Centauri\",\"Barnard's Star\",\"TRAPPIST-1\",\"Wolf 359\"]"
lifespan = "1-10 trillion years"
mass_solar_max = 0.5
mass_solar_min = 0.08
mass_solar_typical = 0.3
temperature_max_kelvin = 3900
temperature_min_kelvin = 2400
temperature_note = ""
temperature_typical_kelvin = 3200
mass_jupiter_max = ""
mass_jupiter_min = ""
mass_jupiter_typical = ""
object_type = ""

[[items]]
code = "L"
slug = "l-type"
name = "L-type Dwarf"
description = "Cool brown dwarfs with water and metal hydride absorption."
abundance_percent = ""
color = "Dark red"
example_stars = "[\"2MASS J0523-1403\",\"DENIS-P J1228.2-1547\"]"
lifespan = ""
mass_solar_max = ""
mass_solar_min = ""
mass_solar_typical = ""
temperature_max_kelvin = 2500
temperature_min_kelvin = 1300
temperature_note = ""
temperature_typical_kelvin = 1900
mass_jupiter_max = 65
mass_jupiter_min = 13
mass_jupiter_typical = 30
object_type = "Brown dwarf or cool star"

[[items]]
code = "T"
slug = "t-type"
name = "T-type Dwarf"
description = "Cool brown dwarfs with methane absorption bands."
abundance_percent = ""
color = "Magenta/Black"
example_stars = "[\"Gliese 570 D\",\"WISE J0350-5658\",\"2MASS J0559-1404\"]"
lifespan = ""
mass_solar_max = ""
mass_solar_min = ""
mass_solar_typical = ""
temperature_max_kelvin = 1500
temperature_min_kelvin = 600
temperature_note = ""
temperature_typical_kelvin = 1000
mass_jupiter_max = 80
mass_jupiter_min = 13
mass_jupiter_typical = 50
object_type = "Brown dwarf"

[[items]]
code = "Y"
slug = "y-type"
name = "Y-type Dwarf"
description = "The coldest brown dwarfs with ammonia absorption features."
abundance_percent = ""
color = "Black (detectable only in infrared)"
example_stars = "[\"WISE J0855-0714\",\"WISE J1828+2650\",\"WISE J1738+2732\"]"
lifespan = ""
mass_solar_max = ""
mass_solar_min = ""
mass_solar_typical = ""
temperature_max_kelvin = 600
temperature_min_kelvin = 200
temperature_note = ""
temperature_typical_kelvin = 400
mass_jupiter_max = 80
mass_jupiter_min = 13
mass_jupiter_typical = 50
object_type = "Brown dwarf"