NGC 4921

NGC 4921 is a large barred spiral galaxy in the Coma Cluster. We find it in the constellation of Coma Berenices. The German-British astronomer William Herschel found it on 11 April 1785. It is about 320 million light-years from Earth.

The galaxy has a nucleus with a bar shape. It has a ring of dust with hot blue stars. Its outer parts have soft, blurry spiral arms. In 1976, the Canadian astronomer Sidney Van den Bergh called NGC 4921 “anemic.” This is because it makes stars very slowly and has a low brightness with faint spiral arms.

Even with these traits, NGC 4921 is the brightest spiral galaxy in the Coma Cluster. It sits close to the cluster’s center and moves faster than most galaxies in the cluster. Studies show that NGC 4921 has very little hydrogen. This is because its gas was taken away by the intergalactic medium. Some of this gas is now returning to the galaxy. This makes NGC 4921 important for learning how galaxies change in cluster areas.

Supernova

One bright explosion, called a supernova, was seen in NGC 4921. It was found on May 4, 1959, by an astronomer named Milton Humason using a special telescope at the Palomar Observatory. This supernova looked like another famous one called SN 1987a.