Stephan's Quintet (NGC 7317-7320)

About this Image

Stephan's Quintet is an excellent example of the tumultuous dynamics of a compact group. The motion of the galaxies through the hot gas, and the gravitational pull of nearby galaxies are stripping cool gas from the galaxies, thereby depriving them of the raw material from which to form new stars. In a few billion years the spiral galaxies in Stephan's Quintet will likely be transformed into elliptical galaxies.

During the past few billion years additional gas may have been stripped from the galaxies in the group and heated by collisions such as the one seen in these images. An intruder that may have passed through the center of the group at least twice is the faint galaxy C seen in the wide field optical image.

The four galaxies NGC 7319, NGC 7318, NGC 7318A, NGC 7317 strung out diagonally (from left to right) across the field are at a distance of about 280 million light years from Earth. The large galaxy NGC 7320 just below the center of this image showing H-alpha areas has now been identified as a foreground galaxy at a distance of about 35 million light years, leaving the group originally identified as Stephan's Quintet with only a quartet of galaxies. However, if we include galaxy NGC 7320C to the left of the cluster, which is at the same distance as the other four galaxies, it becomes a quintet again!

The galaxy cluster is found in the constellation Pegasus approx. 1 degree south of NGC 7331.

North is up.
Below you find a crop on the center of this image in 60/100% size.

References:
Chandra-Xray + DSS (optical) combined image: 1.
Spitzer (IR) + Calar Alto (optical) combined image: 2.
Hubble image: 3.
Hydro Gravitational Theory: 4.