Canon 350D Hap Griffin Baader Mod
36x180sec at iso 1600
30 Darks/Flats/Bias
Celestron 9.25 reduced 0.63

NGC 4631 (with it's companion, Arp 281) is a big beautiful spiral galaxy seen edge-on only 25 million light-years away towards the small northern constellation Canes Venatici. This galaxy's slightly distorted wedge shape suggests to some a cosmic herring and to others the popular moniker of The Whale Galaxy. It is similar in size to our own Milky Way.

A companion galaxy, the small elliptical NGC 4627 appears above the Whale Galaxy. Also at the top of the frame is UGC 7882, a magnitude 15.61 galaxy.


NGC 4631 contains a central starburst, which is a region of intense star formation. The strong star formation is evident in the emission from ionized hydrogen and interstellar dust heated by the stars formed in the starburst. The most massive stars that form in star formation regions only burn hydrogen gas through fusion for a short period of time, after which they explode as supernovae. So many supernovae have exploded in the center of NGC 4631 that they are blowing gas out of the plane of the galaxy. This superwind can be seen in X-rays and in spectral line emission. The gas from this superwind has produced a giant, diffuse corona of hot, X-ray emitting gas around the whole galaxy.


April 5, 2008