A new type of galaxy, so compact that some have previously been misclassified as stars, has been discovered by astronomers led by Michael Gregg of UC Davis and the Lawrence Livermore National Laboratory and Michael Drinkwater of the University of Queensland, Australia.

A galaxy like our own Milky Way is about 100,000 light years across and contains a hundred billion stars. The newly recognized galaxies squeeze their stars into a region only 1/500 the diameter of the Milky Way.

The researchers found the "ultra-compact dwarf galaxies" in the Fornax galaxy cluster, 60 million light years distant from Earth.

The team used the Anglo-Australian Telescope (AAT) at Coonabarabran, Australia, to conduct the initial survey and identify seven ultra-compact dwarf galaxies among 2,500 other objects in the Fornax cluster. They used the Hubble Space Telescope, the European Southern Observatory's Very Large Telescope in Chile and the University of California's Keck Telescope in Hawaii to measure the size of the galaxies and how fast stars are moving within them.

Ultra-compact dwarf galaxies could be the remains of larger objects that have been whittled away over eons by encounters with giant galaxies in the same cluster.

Other team members include: Michael Hilker of Bonn University, Germany; Kenji Bekki and Warrick Couch of the University of New South Wales, Australia; Harry Ferguson of the Space Telescope Science Institute in Baltimore, Md.; Bryn Jones of the University of Nottingham, England; and Steven Philipps of the University of Bristol, England. The finding was reported in the May 29 edition of Nature.