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from http://stardate.org/radio/program.php?f=detail&id=2005-12-08Telescopes are picking up fainter and fainter stars on their edges. As a result, it turns out that many of these galaxies may be a good bit bigger than astronomers had thought -- including our own Milky Way.
One larger galaxy is NGC 300.
Astronomers had pegged its diameter at about 50,000 light-years -- about half the size of the Milky Way. But a few months ago, an international team of astronomers reported that the galaxy is actually twice that size. This extended disk contains lots of faint stars. The number of stars just keeps thinning out as you go farther and farther from the galaxy's core. The team used a giant new telescope in Chile to see the fainter stars.
A few months earlier, another team had reported that the Andromeda galaxy is about three times bigger than previously thought.
The findings suggest that the Milky Way may be bigger than expected, too. It's hard to determine, though, since we're inside the galaxy, so we can't see the whole disk. We have to look through swarms of nearby stars, plus dark clouds of gas, to see its edge.