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OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called
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.
— Scientia Astrophysical Organization's star classification page * Philippe Stee's homepage
Hot and Active Stars Research
O-type stars B-type stars {{star-stub
OB stars are hot, massive stars of spectral types O or early-type B that form in loosely organized groups called OB association
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as ...
s. They are short lived, and thus do not move very far from where they formed within their life. During their lifetime, they will emit much ultraviolet
Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...
radiation. This radiation rapidly ionize
Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecule ...
s the surrounding interstellar gas
In astronomy, the interstellar medium is the matter and radiation that exist in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, as well as dust and cosmic rays. It fills interstella ...
of the giant molecular cloud
A molecular cloud, sometimes called a stellar nursery (if star formation is occurring within), is a type of interstellar cloud, the density and size of which permit absorption nebulae, the formation of molecules (most commonly molecular hydrogen, ...
, forming an H II region
An H II region or HII region is a region of interstellar atomic hydrogen that is ionized. It is typically in a molecular cloud of partially ionized gas in which star formation has recently taken place, with a size ranging from one to hundreds ...
or Strömgren sphere.
In lists of spectra the ''"spectrum of OB"'' refers to ''"unknown, but belonging to an OB association so thus of early type"''.
See also
*O-type main-sequence star
An O-type main-sequence star (O V) is a main-sequence (core hydrogen-burning) star of spectral type O and luminosity class V. These stars have between 15 and 90 times the mass of the Sun and surface temperatures between 30,000 and 50,000 K. ...
* B-type main-sequence star
A B-type main-sequence star (B V) is a main-sequence ( hydrogen-burning) star of spectral type B and luminosity class V. These stars have from 2 to 16 times the mass of the Sun and surface temperatures between 10,000 and 30,000 K. B-type st ...
* Stellar kinematics
In astronomy, stellar kinematics is the observational study or measurement of the kinematics or motions of stars through space.
Stellar kinematics encompasses the measurement of stellar velocities in the Milky Way and its satellites as well as ...
References
* *External links
* Bouy, Hervé and Alves, JoãoCosmography 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.
— Scientia Astrophysical Organization's star classification page * Philippe Stee's homepage
Hot and Active Stars Research
O-type stars B-type stars {{star-stub