M90, a large spiral galaxy in the Virgo Cluster of galaxies, is similar to our Milky Way in both shape and size. There is, however, an important difference between the two: the spiral arms of the Milky Way are sites of active star formation, while those of M90 do not appear to be. Neither its arms nor its disk contains the bright spots and dark clumps that usually signal star formation. Yet M90 is far from dead. Star formation is merely concentrated in its nucleus, which is staggeringly brightΓÇöso much brighter than the arms that at first glance the galaxy looks very much like a single star.
