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Answer: irregular</h2>
According to Hubble galaxies are classified into elliptical, spiral and irregular.
It should be noted this classification is based only on the visual appearance of the galaxy, and does not take into account other aspects, such as the rate of star formation or the activity of the galactic nucleus.
The classification is as follows:
1. Elliptical galaxies: Their main characteristic is that the concentration of stars decreases from the nucleus, which is small and very bright, towards its edges. In addition, they contain a large population of old stars, usually little gas and dust, and some newly formed stars.
2. Spiral galaxies: They have the shape of flattened disks containing some old stars and also a large population of young stars, enough gas and dust, and molecular clouds that are the birthplace of the stars.
3. Irregular Galaxies: Galaxies that do not have well-defined structure and symmetry.
In this context, galaxy M82 does not match with the first two types of galaxies, because it has not a defined shape.
Therefore, M82 is an irregular galaxy.
