| Description | This is another William Herschel discovery from 1788, an irregular Magellanic type galaxy. "Irregular" in that it doesn't fit into the standard shape classification scheme. The "normal" classifications starts with a spiral, indicating a relatively new galaxy with an obvious structure, made up (usually) of two or more arms, and ends with elliptical (old, devoid of structure), with lenticular features in the middle. By contrast, C21 is boxy and consists of one, big arm (hence Magellanic, one-armed), in the same way that the large Magellanic Cloud appears relative to the Milky Way. C21/NGC 4449 is considered a starburst galaxy due to its high rate of star formation, twice the rate of the LMC. You can see evidence of this activity in the multiple "knots" along the edges and connected to the surface. |
