July 19, 2001
Photo No: H2001-22
Star Clusters Born in the Wreckage of Cosmic Collisons
This close-up view of Stephan's Quintet, a group of five
galaxies, reveals a string of bright star clusters that
sparkles like a diamond necklace. The clusters, each
harboring up to millions of stars, were born from the
violent interactions between some members of the group.
The rude encounters also have distorted the galaxies'
shapes, creating elongated spiral arms and long,
The NASA Hubble Space Telescope photo showcases three
regions of star birth: the long, sweeping tail and
spiral arms of NGC 7319 [near center]; the gaseous debris
of two galaxies, NGC 7318B and NGC 7318A [top right]; and
the area north of those galaxies, dubbed the northern
starburst region [top left].
The clusters' bluish color indicates that they're
relatively young. Their ages span from about 2 million
to more than 1 billion years old.
The brilliant star clusters in NGC 7318B's spiral arm
(about 30,000 light-years long) and the northern starburst
region are between 2 million and more than 100 million
years old. NGC 7318B instigated the starburst by barreling
through the region. The bully galaxy is just below
NGC 7318A at top right. Although NGC 7318B appears
dangerously close to NGC 7318A, it's traveling too fast
to merge with its close neighbor. The partial galaxy on the
far right is NGC 7320, a foreground galaxy not physically
bound to the other galaxies in the picture.
About 20 to 50 of the clusters in the northern starburst
region reside far from the coziness of galaxies. The
clusters were born about 150,000 light-years from the
A galaxy that is no longer part of the group triggered
another collision that wreaked havoc. NGC 7320C [not in
the photo] plowed through the quintet several hundred
million years ago, pulling out the 100,000 light-year-long
tail of gaseous debris from NGC 7319. The clusters in
NGC 7319's streaming tail are 10 million to 500 million
years old and may have formed at the time of the violent
collision. The faint bluish object at the tip of the tail
is a young dwarf galaxy, which formed in the gaseous debris.
The quintet is in the constellation Pegasus, 270 million
light-years from Earth. Spied by Edouard M. Stephan in 1877,
Stephan's Quintet is the first compact group ever discovered.
The mosaic picture was taken by Hubble's Wide Field and
Planetary Camera 2 on Dec. 30, 1998 and June 17, 1999.
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)