In the northern sky, just off the bowl of the Big Dipper, two galaxies are locked in a slow-motion collision that's been unfolding for hundreds of millions of years. Astronomers call them M81 and M82. We call them cosmic bumper cars.
M81 — Bode's Galaxy — is a grand spiral, a near-twin of our own Milky Way about 12 million light years away. It's bright enough to spot with ordinary binoculars from a dark site, which makes it one of the most distant objects most people will ever see with such modest equipment. At its core sits a supermassive black hole roughly 15 times the mass of the one at the center of our galaxy.
Its neighbor M82, the Cigar Galaxy, is the one that got the worst of the encounter. A close pass between the two galaxies hundreds of millions of years ago compressed M82's gas clouds and ignited a firestorm of star birth. M82 is what astronomers call a starburst galaxy: it's forming new stars at roughly ten times the rate of the Milky Way, and the energy from all those young stars is blasting plumes of glowing gas out of the galaxy's disk.
There's even a third party in the wreck: Holmberg IX, a small dwarf galaxy thought to have formed from debris pulled loose during the encounter — a galaxy made from the shrapnel of a collision between two others.
The pair sits close together in the sky, and from a dark location both fit in the same binocular field of view. M81 appears as a soft oval glow, M82 as a thin gray streak — and once you know what you're looking at, the sight gets more impressive, not less. You're watching a gravitational interaction with a combined audience of hundreds of billions of stars.
On our late night tours, M81 and M82 are regular targets through the telescope. Ask your guide to show you the bumper cars — and to point out which one is winning.
