For comparison, the Milky Way is over 100,000 light-years in diameter. The UCDs are not much more than 100 light-years across.Universe's smallest galaxies discovered
A team of scientists led by the University of Bristol has discovered a new class of galaxy - the first such discovery since the 1930s.
The Hubble Space Telescope was used to study the seven new galaxies, which have been named ultra-compact dwarfs (UCDs).
The galaxies - in a cluster 60 million light-years away - are so small that on ordinary photographs, they look like individual stars.
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