Star Colours
Colour Variation in M80's Stars
M80 is one of the Milky Way's densest globular clusters. It contains hundreds of thousands of stars bound tightly by gravity. Globular clusters stars are mostly the same age, and very old, for they formed during the birth of the Milky Way. Star masses range from sun-size down to the smallest Red Dwarfs. One by one, the larger stars are exhausting their hydrogen supply and expanding into Red Giants.In this Hubble Telescope image, many bright Red Giants are visible.
Globular clusters also contain "blue stragglers" in their cores. These stars appear younger and more massive than the other cluster stars. Stars collide in densely populated cores and sometimes they merge to form heavier, youthful stars.
Until this image was made, blue stragglers had not been seen in M80. We now know there are more than twice as many as any of the globulars surveyed so far. The collision rate in M80 must be exceptionally high.
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This image was created from separate HST exposures by different teams in 1994 and 1999. One team searching for blue stragglers. The other team was studying dwarf novae. Each team used different colour filters. This composite image was generated by combining the various single colour images. See STSCI Press Release 1999 26 for details.