Galaxy AM 0644-741 in Volans: The Lure of The Rings | Hubble Space Telescope

Galaxy AM 0644-741 in Volans: The Lure of The Rings | Hubble Space Telescope

Resembling a diamond-encrusted bracelet, a ring of brilliant blue star clusters wraps around the yellowish nucleus of what was once a normal spiral galaxy in this image from the NASA/European Space Agency Hubble Space Telescope (HST). Hubble was launched on April 24, 1990 and was deployed from the space shuttle Discovery on April 25, 1990.

The sparkling blue ring is 150,000 light-years in diameter, making it larger than our entire home galaxy, the Milky Way. The galaxy, cataloged as AM 0644-741, is a member of the class of so- called "ring galaxies." It lies 300 million light-years away in the direction of the southern constellation Volans.

Ring galaxies arise from a collision where one galaxy plunges directly through the disk of another one. The prominent ring of galaxy AM 0644-741 is the result of a hit-and-run event by a celestial neighbor. The spiral galaxy visible to the left of AM 0644-741 is not the culprit, as it is actually a background galaxy that is not interacting with the ring galaxy at all. The true perpetrator has been identified by astronomers, but is outside the field of view of this image.

The gravitational shock imparted by a collision of this kind drastically changes the orbits of stars and gas in the "target" galaxy's disk, causing them to rush outward. As the ring plows outward into its surroundings, gas clouds collide and are compressed. The clouds can then contract under their own gravity, collapse, and form an abundance of new stars.

The rampant star formation explains why the ring here is so blue: It is continuously forming massive, young, hot stars that are blue in color. Associated with them are the pink regions visible along the ring. These are rarefied clouds of glowing hydrogen gas, fluorescing because of the strong ultraviolet light from the newly formed massive stars.

Credit: NASA, ESA, and The Hubble Heritage Team (AURA/STScI)
Release Date: April 22, 2004

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