NGC 7318, Stephans Quintet

Stephan’s Quintet, NGC 8318  Stephan’s Qunitet was identified by Edouard M. Stephan in 1877 and is the first group of interacting galaxies ever discovered.  This image was  constructed with data drawn from the extensive Hubble Legacy Archive. Stephan’s Quintet lies within the boundaries of the high flying northern constellation, Pegasus.  At the 300 million light years estimated distance this field of view spans about 500,000 light-years. Only four of these five galaxies are actually locked in a cosmic dance of repeated close encounters. The odd man out is easy to spot, though. The interacting galaxies NGC 7319(top), NGC 7318A,B(center), NGC 7317(bottom) have an overall yellowish cast. They also tend to have distorted loops and tails, grown under the influence of disruptive gravitational tides. But the predominantly bluish galaxy, NGC 7320, is closer, just 40 million light-years distant, and isn’t part of the interacting group. In the upper galaxy of the quartet nearly all of the neutral hydrogen has been stripped out most likely as a result of a collision with NGC 7320C(not seen above the image) some 100 million years ago. A pair of long, parallel tidal tails extend southward from NGC 7319 in the direction of NGC 7320c, and is undergoing star formation.  Another facet of the activity here  has been identified by  the Spitzer Space Telescope showing that NGC 7318B is colliding with the group at a speed greater than 900 km/sec producing a curved shock wave.

The raw data for this image was taken by the Hubble telescope in September 2009 and the processing was done by Michael Adler in 2021. This is a true color image with the color resulting from assigning different hues (colors) to each monochromatic image taken through various filters. In this case, the assigned colors are: Blue: from a 435nm broadband filter, Green: 606nm filter, Red: 814nm filter, and red highlights from Hydrogen and Nitrogen emission from a narrowband 669nm filter.