NGC 4631 - Whale Galaxy
The galaxy NGC 4631, also known as the Whale Galaxy, is a spiral galaxy of the Hubble Type SBc. It was discovered in March 1787 by the astronomer
F.W. Herschel. It is located in the constellation Canes Venatici, has an apparent magnitude of about 9.8mag, and is about 25 million light-years away from
Earth. Its size is estimated to be around 80,000 light-years, which makes it slightly smaller than our own Milky Way.
The most striking feature of NGC 4631 is its deformed, elongated halo, which indicates a strong interaction with its companion galaxies. In particular,
NGC 4627, a dwarf galaxy, is very close to the galaxy and is probably partly responsible for the asymmetrical shape of NGC 4631.
At the center of NGC 4631 there is a supermassive black hole (SMBH) with an estimated mass of about 1 million solar masses. X-ray observations have
shown that this black hole is active but does not emit particularly strong radiation. Interestingly, a high star formation rate has also been observed in the
center of NGC 4631, suggesting that the existence of the black hole and the star formation may be related.
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The view of NGC 4631 in a 20" telescope at high magnifications is simply phenomenal. If you spend some time observing the galaxy, you will notice
details everywhere in the halo. I never thought I would see so many details. It is therefore worth dedicating more observation time to the galaxy.
First of all, several dust clouds can be seen within the galaxy. The first small cloud is located to the right of a faint HII region and two prominent
clouds merge into the galaxy's halo from above. The largest dust cloud is located near the center of NGC 4631, with more dark areas to the right.
The many HII regions, which were best visible at 380x, are also particularly interesting. Some of the diffuse objects had a faint dot in the center -
these are estimated to be SSCs (Super Star Clusters), i.e., very young and luminous open star clusters with many hot blue stars. It is pretty amazing to
see such objects with your own eyes at a distance of 25 million light-years. :) So cool!
Another exciting feature is a star cloud protruding downwards from the halo on the left (eastern) side of the galaxy. Here, I could also see an HII region
at 380x.
