April 5, 2001: New pictures from the Hubble telescope are giving astronomers a detailed view of the Whirlpool galaxy's spiral arms and dust clouds, which are the birth sites of massive and luminous stars. This galaxy, also called M51 or NGC 5194, is having a close encounter with a nearby companion galaxy, NGC 5195, just off the upper edge of this image. The companion's gravitational influence is triggering star formation in the Whirlpool, as seen by the numerous clusters of bright, young stars [highlighted in red].
This Hubble photo is giving astronomers an unprecedented view of the intricate structure of the Whirlpool's spiral arms and dust clouds. Astronomers are seeing dust "spurs" along the spiral arms that branch out almost perpendicular to the main spiral arms. The regularity and large number of these spurs suggests that astronomers may have to rethink the popular theory that a spiral galaxy has two arms. The new image also reveals a dust disk in the center of the galaxy, which may feed a black hole.