page_title: O-type star
section_title: Main-sequence
hierarchical_section_title: O-type star / Examples / Main-sequence
context_page_description: An O-type star is a hot, blue-white star of spectral type O in the Yerkes classification system employed by astronomers. They have temperatures in excess of 30,000 kelvin. Stars of this type have strong absorption lines of ionised helium, strong lines of other ionised elements, and hydrogen and neutral helium lines weaker than spectral type B.
  Stars of this type are very rare, but because they are very bright, they can be seen at great distances and four of the 90 brightest stars as seen from Earth are O type. Due to their high mass, O-type stars end their lives rather quickly in violent supernova explosions, resulting in black holes or neutron stars. Most of these stars are young massive main sequence, giant, or supergiant stars, but the central stars of planetary nebulae, old low-mass stars near the end of their lives, also usually have O spectra.
  O-type stars are typically located in regions of active star formation, such as the spiral arms of a spiral galaxy or a pair of galaxies undergoing collision and merger. These stars illuminate any surrounding material and are largely responsible for the distinct coloration of a galaxy's arms.
context_section_description: 9 Sagittarii
  10 Lacertae
  AE Aurigae
  BI 253
  Delta Circini
  HD 93205 (V560 Carinae)
  Mu Columbae
  Sigma Orionis
  Theta1 Orionis C
  VFTS 102
  Zeta Ophiuchi
caption: The brightest star in the Trapezium cluster is O7V star θ1 Orionis C. The other three are B0.5 and B1 main-sequence stars.
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