January 8, 2008
Cosmic Blue Blobs Discovered
AUSTIN, Texas — Brilliant blue blobs weighing
tens of thousands of solar masses have been found lurking in the seemingly
barren expanse of intergalactic space. The "eyes" of the Hubble
Space Telescope resolved the objects, which appear to be clusters of stars
born in the swirls and eddies of a galactic smashup some 200 million years ago.
mysterious star clusters are considered orphaned, as they don't belong to any
particular galaxy. Instead, they are clumped together into a structure called
Arp's Loop along a wispy bridge of gas stretched like taffy between three
colliding galaxies — M81, M82 and NGC 3077. These galaxies are located about 12
million light-years from us in the constellation Ursa Major.
could not believe it, the stars were in the middle of nowhere," said
Duilia de Mello of the Catholic University of America in Washington, D.C., and NASA's Goddard Space Flight Center.
reported the findings here today at a meeting of the American Astronomical
had not considered the gas tendrils thick enough to accumulate enough material
needed to build so many stars. But the new images reveal they hold the
star-equivalent of five Orion
massive than most open clusters housed inside galaxies, the blue blobs are just
a fraction of the mass of globular star clusters that orbit a galaxy. The
astronomers estimate that many of the clusters' stars are as young as 10
million years and younger. Our sun, for comparison, is 4.6 billion years old.
and her colleagues suggest galactic collisions and the turbulent aftermaths
might have triggered the starbirth. In fact, it was about 200 million years ago
that M81 and M82 had their last encounter.
collisions like this one, which would enhance locally the density of gas
streams, were much more common in the early universe, they say. And so such
blue blobs would have been more common as well in the early universe.
Once the clustered
stars had burned out or exploded, the heavier elements would have been ejected
into intergalactic space. The fact that the blue-blob clusters are not
associated with any galaxy means such elements produced during fusion in their
nuclear furnaces would be easily expelled.