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OB star

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Type of hot, massive star

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Find sources: "OB star" – news ·newspapers ·books ·scholar ·JSTOR(June 2016)

OB stars are hot,massive stars of spectral typesO orearly-type B that form in loosely organized groups calledOB associations. They are short lived, and thus do not move very far from where they formed within their life. During their lifetime, they will emit muchultraviolet radiation. This radiation rapidlyionizes the surroundinginterstellar gas of thegiant molecular cloud, forming anH II region orStrömgren sphere.

In lists of spectra the "spectrum of OB" refers to "unknown, but belonging to an OB association so thus of early type".^{[dubious –discuss]}

Bouy, Hervé and Alves, João:Cosmography of OB Stars in the Solar Neighborhood Astronomy & Astrophysics (December 2015). A three-dimensional map of OB star density within 500 pc of the Sun.
[1] — Scientia Astrophysical Organization's star classification page
Philippe Stee's homepage:Hot and Active Stars Research

Early Late Main sequence O B A F G K M Subdwarf O B WR OB Subgiant Giant Blue Red Yellow Bright giant Supergiant Blue Red Yellow Hypergiant Yellow Carbon S CN CH White dwarf Chemically peculiar Am Ap/Bp CEMP HgMn He-weak Barium Lambda Boötis Lead Technetium Be Shell B[e] Helium Extreme Blue straggler
Remnants	Compact star Parker's star White dwarf Helium planet Neutron Radio-quiet Pulsar Binary X-ray Magnetar Stellar black hole X-ray binary Burster SGR
Hypothetical	Blue dwarf Black dwarf Exotic Boson Electroweak Strange Preon Planck Dark Dark-energy Quark Q Black hole star Black Hawking Quasi-star Gravastar Thorne–Żytkow object Iron Blitzar White hole