Fine details of the dark band are revealed in this image of the central portion of M64 obtained with the Hubble Space Telescope. M64 is well known among amateur astronomers because of its appearance in small telescopes. It was first cataloged in the 18th century by the French astronomer Messier. Located in the northern constellation Coma Berenices, M64 resides roughly 17 million light-years from Earth.

At first glance, M64 appears to be a fairly normal pinwheel-shaped spiral galaxy. As in the majority of galaxies, all of the stars in M64 are rotating in the same direction, clockwise as seen in the Hubble image. However, detailed studies in the 1990's led to the remarkable discovery that the interstellar gas in the outer regions of M64 rotates in the opposite direction from the gas and stars in the inner regions.

Active formation of new stars is occurring in the shear region where the oppositely rotating gases collide, are compressed, and contract. Particularly noticeable in the image are hot, blue young stars that have just formed, along with pink clouds of glowing hydrogen gas that fluoresce when exposed to ultraviolet light from newly formed stars.

Astronomers believe that the oppositely rotating gas arose when M64 absorbed a satellite galaxy that collided with it, perhaps more than one billion years ago. This small galaxy has now been almost completely destroyed, but signs of the collision persist in the backward motion of gas at the outer edge of M64.

This image of M64 was taken with Hubble's Wide Field Planetary Camera 2 (WFPC2) in 2001. The color image is a composite prepared by the Hubble Heritage Team from pictures taken through four different color filters. These filters isolate blue and near-infrared light, along with red light emitted by hydrogen atoms and green light from Stromgren y.

Image Credit: NASA and The Hubble Heritage Team (AURA/STScI) Acknowledgment: S. Smartt (Institute of Astronomy) and D. Richstone (U. Michigan)

NOTE TO EDITORS: For additional information, please contact Keith Noll, Hubble Heritage Team, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, (phone) 410-338-1828, (fax) 410-338-4579, (e-mail) noll@stsci.edu or

Howard Bond, Hubble Heritage Team, Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, (phone) 410-338-4718, (fax) 410-338-4579, (e-mail) bond@stsci.edu

Electronic images and additional information are available at

• http://hubblesite.org/news/2004/04
• http://heritage.stsci.edu/2004/04

The Space Telescope Science Institute (STScI) is operated by the Association of Universities for Research in Astronomy, Inc. (AURA), for NASA, under contract with the Goddard Space Flight Center, Greenbelt, MD. The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA).