[14][15] 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.

The arms had been missed due to M82's high disk surface brightness, the nearly edge-on view of this galaxy (~80°),[7] and obscuration by a complex network of dusty filaments in its optical images.

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.

[23][24] Apparent superluminal motion is consistent with relativistic jets in massive black holes and does not indicate that the source itself is moving above lightspeed.

Tidal forces caused by gravity have deformed M82, a process that started about 100 million years ago.

M82 has undergone at least one tidal encounter with M81 resulting in a large amount of gas being funneled into the galaxy's core over the last 200 Myr.

[7] The most recent such encounter is thought to have happened around 2–5×108 years ago and resulted in a concentrated starburst together with a corresponding marked peak in the cluster age distribution.

[7] Stars in M82's disk seem to have been formed in a burst 500 million years ago, leaving its disk littered with hundreds of clusters with properties similar to globular clusters (but younger), and stopped 100 million years ago with no star formation taking place in this galaxy outside the central starburst and, at low levels since 1 billion years ago, on its halo.

A suggestion to explain those features is that M82 was previously a low surface brightness galaxy where star formation was triggered due to interactions with its giant neighbor.

[27][2] As a starburst galaxy, Messier 82 is prone to frequent supernova, caused by the collapse of young, massive stars.

[31] On 21 January 2014 at 19.20 UT, a new distinct star was observed in M82, at apparent magnitude +11.7, by astrophysics lecturer Steve Fossey and four of his students, at the University of London Observatory.

It was initially suggested that it could become as bright as magnitude +8.5, well within the visual range of small telescopes and large binoculars,[32] but peaked at fainter +10.5 on the last day of the month.