From Minneapolis, at a meeting of the American Astronomical Society
Visible even to the naked eye, the starlit, spiral disk of the Andromeda galaxy stretches across a patch of sky as wide as the full moon. A new investigation of Earth's next-door-neighbor galaxy reveals that it looms even larger. Using a spectrograph on the Keck II Telescope atop Hawaii's Mauna Kea, astronomers have found that the diameter of Andromeda's disk spans about 220,000 light-years. That's three times the size of previous estimates.