Andromeda, look how you've grown!

"The lovely Andromeda galaxy appeared as a warm, fuzzy blob to the ancients. To modern astronomers, millennia later, it [offers] an excellent opportunity to better understand the universe. In the latter regard, our nearest galactic neighbor is a gift that keeps on giving.

"Scott Chapman from the California Institute of Technology and Rodrigo Ibata from the Observatoire Astronomique de Strasbourg in France have led a team of astronomers in a project to map out the detailed motions of stars in the outskirts of the Andromeda galaxy. Their recent observations with the Keck telescopes show that the tenuous sprinkle of stars that extend outward from the galaxy are actually part of the main disk itself. This means that the spiral disk of stars in Andromeda is three times larger in diameter than previously estimated."