SYDNEY: The Milky Way could be surrounded by up to 2,000 small galaxies, too faint to be seen with current technology, say astrophysicists.

Their research has implications for understanding how galaxies form and the nature of dark matter – the invisible matter that pervades and surrounds all galaxies, including our own.

Astronomers know of 24 satellite galaxies of the Milky Way, including the two bright Magellanic Clouds, which on dark nights are visible just to the side of the wide band of the Milky Way.

But the U.S. researchers, led by astrophysicist Erik Tollerud from the University of California, Irvine, say there are at least 400 and as many as 2,000 more satellite galaxies – we just haven't spotted them yet because they are so faint.