O-type star

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O-type star

astronomy

Also known as: O star

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Last updated

July 1, 2026

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O-type stars are the hottest and most luminous stars, with surface temperatures typically ranging from 25,000 to 50,000 Kelvin. They appear bluish-white and are characterized by the presence of ionized helium lines in their spectra. These stars are also classified as "extreme Population I" objects, indicating they are relatively young and found in the arms of galaxies like the Milky Way. O-type stars are massive and have a high rate of energy conversion, meaning they evolve and exhaust their fuel much faster than less massive stars like our Sun.1234

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stellar classification
Class O includes bluish white stars with surface temperatures typically of 25,000–50,000 K (although a few O-type stars with vastly greater temperatures have been described); lines of ionized helium appear in the spectra. Class B stars typically range from 10,000 K to 25,000 K and…
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Class O includes bluish white stars with surface temperatures typically of 25,000–50,000 K (although a few O-type stars with vastly greater temperatures have been described); lines of ionized helium appear in the spectra. Class B stars typically range from 10,000 K to 25,000 K and…
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diffuse ionized gas
…of the luminosity of all O and B stars. This energy output is about equal to the total power provided by supernovae, but the latter radiate most of their energy either in nonionizing radiation or in providing kinetic energies to their expanding shells. Other potential energy sources fall far short.
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…of the luminosity of all O and B stars. This energy output is about equal to the total power provided by supernovae, but the latter radiate most of their energy either in nonionizing radiation or in providing kinetic energies to their expanding shells. Other potential energy sources fall far short.
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Populations I and II
…as the very hot blue-white O and B types (some of which are less than one million years old), are designated as extreme Population I objects. All known Population I members occur near and in the arms of the Milky Way system and other spiral galaxies. They also have been…
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…as the very hot blue-white O and B types (some of which are less than one million years old), are designated as extreme Population I objects. All known Population I members occur near and in the arms of the Milky Way system and other spiral galaxies. They also have been…
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Milky Way Galaxy
Stellar associations
…young stars of spectral types O and B. They have absolute luminosities as bright as any star in the Galaxy—on the order of one million times the luminosity of the Sun. Such stars have very short lifetimes, only lasting a few million years. With luminous stars of this type there…
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…young stars of spectral types O and B. They have absolute luminosities as bright as any star in the Galaxy—on the order of one million times the luminosity of the Sun. Such stars have very short lifetimes, only lasting a few million years. With luminous stars of this type there…
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