The starburst activity is thought to have been triggered by interaction with neighboring galaxy M81. As the closest starburst galaxy to Earth, M82 is the prototypical example of this galaxy type. SN 2014J, a type Ia supernova, was discovered in the galaxy on 21 January 2014. In 2014, in studying M82, scientists discovered the brightest pulsar yet known, designated M82 X-2.
M82, with M81, was discovered by Johann Elert Bode in 1774; he described it as a "nebulous patch", this one about 3⁄4 degree away from the other, "very pale and of elongated shape".
In 1779, Pierre Méchain independently rediscovered both objects and reported them to Charles Messier, who added them to his catalog.
M82 was believed to be an irregular galaxy. In 2005, however, two symmetric spiral arms were discovered in near-infrared (NIR) images of M82. The arms were detected by subtracting an axisymmetric exponential disk from the NIR images.
Even though the arms were detected in NIR images, they are bluer than the disk. The arms had been missed due to M82's high disk surface brightness, the nearly edge-on view of this galaxy (~80°), and obscuration by a complex network of dusty filaments in its optical images. These arms emanate from the ends of the NIR bar and can be followed for the length of 3 disc scales.
Assuming that the northern part of M82 is nearer to us, as most of the literature does, the observed sense of rotation implies trailing arms.
M82 is being physically affected by its larger neighbor, the spiral M81. Tidal forces caused by gravity have deformed M82, a process that started about 100 million years ago. This interaction has caused star formation to increase tenfold compared to "normal" galaxies.
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