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News Release Archive:

News Release 138 of 291

February 5, 2004 09:00 AM (EST)

News Release Number: STScI-2004-04

An Abrasive Collision Gives One Galaxy a "Black Eye"

A Hubble Heritage Release

February 5, 2004: A collision of two galaxies has left a merged star system with an unusual appearance as well as bizarre internal motions. Messier 64 (M64) has a spectacular dark band of absorbing dust in front of the galaxy's bright nucleus, giving rise to its nicknames of the "Black Eye" or "Evil Eye" galaxy.

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Q & A: Understanding the Discovery

  1. 1. Why is this galaxy called the "Black Eye" galaxy?


  2. Messier 64 (M64) has a spectacular dark band of absorbing dust surrounding the galaxy's bright nucleus on the side closest to Earth, giving rise to its nicknames of the "Black Eye" or "Evil Eye" galaxy. M64 is well known among amateur astronomers because of its appearance in small telescopes.

  3. 2. What is notable about the motions of this galaxy?


  4. 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, the interstellar gas in the outer regions of M64 rotates in the opposite direction from the gas and stars in the inner regions.

  5. 3. What caused the backwards rotation of the gas in the center of this galaxy?


  6. 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.

  7. 4. Are there new stars forming in this galaxy?


  8. 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.

  9. 5. What do the colors mean in this image?


  10. This image of M64 was taken with Hubble's Wide Field Planetary Camera 2 (WFPC2). 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 (red), along with red light emitted by hydrogen atoms (pink in this image) and green light from Strömgren y.

 
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Credit: NASA and The Hubble Heritage Team (AURA/STScI)

Acknowledgment: S. Smartt (Institute of Astronomy) and D. Richstone (U. Michigan)