Stephan's Quintet

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Christopher K.
Posts: 4804
Joined: October 12th, 2009, 3:28 pm
Location: Baton Rouge, LA

Stephan's Quintet

Post by Christopher K. » December 7th, 2010, 11:27 pm

Stephan's Quintet consists of five galaxies in the constellation Pegasus. Four of the five are gravitationally associated with one another and lie about 250 million light-years distant; they are also involved in a collision. This collision has led to a depletion of hydrogen gas in the foursome. "Intruder" NGC 7318b is smashing through the center of the remaining trio.

Philip Appleton (of the Herschel Science Center) and colleagues, however, obtained infrared evidence in 2004 of almost pure molecular hydrogen. They wondered if the distribution was even over the entire shock wave created by the ongoing collision. In 2008, they had a second chance (using Spitzer again) to image the cluster, and once again saw widespread molecular hydrogen through the shock wave, and then some.

A key question is, what's powering the hydrogen? The team believes since molecular hydrogen in dense clumps dampens its tendency to break apart when disturbed, the main shock wave may not have a chance to "get at" the molecules buried in the clumps. At least, that's how I understand it.

The cluster was discovered by Éouard Stephan in 1877.

More Information:
January 2011 Astronomy, pp. 34-39
http://www.spitzer.caltech.edu/images/1 ... -s-Quintet
http://chandra.harvard.edu/photo/2009/stephq/
http://photojournal.jpl.nasa.gov/catalog/PIA02587
http://www.daviddarling.info/encycloped ... intet.html

Christopher K.
Posts: 4804
Joined: October 12th, 2009, 3:28 pm
Location: Baton Rouge, LA

Re: Stephan's Quintet

Post by Christopher K. » February 25th, 2012, 5:34 pm

Today's APOD of Stephan's Quintet is from the Hubble archive and covers half-a-million light-years. Above the two interacting the closest (NGC 7318A and NGC 7318B) there is a faint bluish region--a "starburst" area where new stars are coming into being.

The image:
http://apod.nasa.gov/apod/ap120225.html

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