Radiation astronomy/Hypervelocity stars

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The Hubble Space Telescope image shows four high-velocity, runaway stars plowing through their local interstellar medium. Credit: NASA - Hubble's Advanced Camera for Surveys.

Def. a star moving faster than 65 km/s to 100 km/s relative to the average motion of the stars in the Sun's neighbourhood is called a high-velocity star.

Def. a high-velocity star moving through space with an abnormally high velocity relative to the surrounding interstellar medium is called a runaway star.

Def. a star whose elliptical orbit takes it well outside the plane of [its galaxy] at steep angles is called a halo star.


This ultraviolet-wavelength image mosaic, taken by NASA's Galaxy Evolution Explorer (GALEX), shows a comet-like "tail" stretching 13 light year across space. Credit: NASA.

The image on the left shows a high velocity binary star and the comet-like trail behind it is light years long. The binary is plowing through the interstellar medium. It's radiating, been radiated, and packs a punch!