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News Release 650 of 1051

July 19, 2001 09:00 AM (EDT)

News Release Number: STScI-2001-22

Star Clusters Born in the Wreckage of Cosmic Collisions

July 19, 2001: In the beginning of the 1946 holiday film classic "It's a Wonderful Life," angelic figures take on the form of a famous group of compact galaxies known as Stephan's Quintet. In reality, these galaxies aren't so WATCH: HubbleMinute Video HubbleMinute: Battle Royale in Stephan's Quintet HubbleMinute: Battle Royale in Stephan's Quintet  heavenly. Pictures from the Hubble telescope show that Stephan's Quintet has been doing some devilish things. At least two of the galaxies have been involved in high-speed, hit-and-run accidents, which have ripped stars and gas from neighboring galaxies and tossed them into space. But the galactic carnage also has spawned new life. Arising from the wreckage are more than 100 star clusters and several dwarf galaxies. The young clusters, each harboring up to millions of stars, are shown clearly for the first time in pictures taken by Hubble's Wide Field and Planetary Camera 2.

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Q & A: Understanding the Discovery

  1. 1. Where are the star clusters and dwarf galaxies?

  2. Astronomers identified three significant regions of star formation, which were probably created by two separate encounters. They found clusters in the long, sweeping tail and spiral arms of NGC 7319 [near center of picture]; in the tidal debris of two galaxies, NGC 7318B and NGC 7318A [top right]; and in an area north of those galaxies, dubbed the "northern starburst region" [top left]. Please refer to the illustrations for a locator map

    The dwarf galaxies were born alongside several of the star clusters. As many as 15 dwarf galaxies are found in NGC 7319's long tail.

  3. 2. How old are the star clusters?

  4. The clusters span a range of ages, from about 2 million to more than 1 billion years old, indicating a long history of rude encounters among members of this group. The clusters' ages indicate when the galactic encounters occurred. That's because the clusters formed as a result of gravitational interactions between some members of the quintet, which compressed clouds of hydrogen gas and created stars.

  5. 3. Why do astronomers study galactic encounters?

  6. Studying the star clusters and dwarf galaxies in Stephan's Quintet provides insights into how galactic encounters may have driven galaxy evolution in the early universe. Galaxies interacted more often in the early universe because they were closer together.

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Image Credits: NASA, Jayanne English (University of Manitoba), Sally Hunsberger (Pennsylvania State University), Zolt Levay (Space Telescope Science Institute), Sarah Gallagher (Pennsylvania State University), and Jane Charlton (Pennsylvania State University)

Science Credits: Sarah Gallagher (Pennsylvania State University), Jane Charlton (Pennsylvania State University), Sally Hunsberger (Pennsylvania State University), Dennis Zaritsky (University of Arizona), and Bradley Whitmore (Space Telescope Science Institute)