(Left) A GALEX ultraviolet image of the interacting galaxies M81 and M82, which lie 12 million light-years away in the constellation Ursa Major. (Right) A Hubble Space Telescope visible light image of bright blue star clusters found along a wispy bridge of gas that was tidally stretched between the two galaxies, and a third companion galaxy not seen in this picture.
Credit: NASA, ESA, and D. de Mello (Catholic University of America/GSFC)
Hubble Space Telescope’s powerful vision has resolved strange objects nicknamed “blue blobs” and found them to be brilliant blue clusters of stars born in the swirls and eddies of a galactic smashup 200 million years ago. Such “blue blobs”—weighing tens of thousands of solar masses—have never been seen in detail before in such sparse locations, say researchers. The “blue blobs” are found along a wispy bridge of gas strung among three colliding galaxies, M81, M82, and NGC 3077, residing about 12 million light-years away from Earth.
This is not the place astronomers expect to find star clusters, because the gas filaments were considered too thin to accumulate enough material to actually build these many stars. The star clusters in this diffuse structure might have formed from gas collisions and subsequent turbulence, which enhanced locally the density of the gas streams. Galaxy collisions were much more frequent in the early universe, so “blue blobs” should have been common. After the stars burned out or exploded, the heavier elements forged in their nuclear furnaces would have been ejected to enrich intergalactic space.