Runaway star

Runaway stars (also known as outliers ) are stars of the spectral type  O or B, which, compared to neighboring stars, move their orbit through the Milky Way exceptionally quickly - with radial speeds between around 30 and 200 km / s . In many cases, the proper movement of a runaway star points exactly away from a star association of which it was likely to have been a member earlier and from which it was then thrown out.

Two possibilities are considered to explain this throwing out:

• According to one theory, a supernova explosion in a multiple star system caused the other components to be driven away as "outliers" by energy transfer.
• The other theory assumes that two binary stars came so close that some of their components were shot away at high speeds due to gravitational interaction.

The best-known examples are the stars AE Aurigae , My Columbae and 53 Arietis , which move from each other at more than 100 km / s. If one calculates back their space orbits from their speeds and directions of movement , it turns out that they intersected about 3 million years ago near the Orion Nebula , from which it is concluded that the three stars belonged to the Orion Association earlier . Other examples of “outliers” are Zeta Ophiuchi and 68 Cygni .

literature

• Runaway stars. In: The Brockhaus. Astronomy . 2006, p. 395.
• Meyer's Handbook of Space . 7th edition 1994, p. 362f.