Messier 82: The Cigar Galaxy

Messier 82, the Cigar Galaxy, is a narrow streak of light just north of M81 in Ursa Major. It is the best-known starburst galaxy in the sky, a galaxy forming new stars at a furious pace.

What it is

M82 is a disk galaxy seen nearly edge-on, about 12 million light-years away. Its visible length of about 9 arcminutes corresponds to roughly 30,000 light-years. It was long classed as irregular because of its chaotic look, but infrared images later revealed spiral arms, and NASA now lists it as a spiral.

Its center is forming stars about 10 times faster than the entire Milky Way. The trigger was a close pass by its larger neighbor M81, whose gravity stirred up M82's gas. The many massive young stars and their supernovae drive a strong wind that blows gas out above and below the disk, seen in deep images as red filaments of glowing hydrogen. M82 is also the brightest galaxy in the sky in infrared light. NASA expects the starburst to die down within a few tens of millions of years. In January 2014 a Type Ia supernova, SN 2014J, appeared in M82 and reached about magnitude 11, bright enough for backyard telescopes.

When to see it

Like M81, M82 is circumpolar from 40°N and never sets. It is best on spring evenings, crossing the meridian high in the north around 10 p.m. in mid-March and about 8 p.m. in mid-April, when it climbs to about 61°. From the Southern Hemisphere it can be seen only from the tropics, low in the north.

How to find it

Draw a line from Phecda to Dubhe across the bowl of the Big Dipper and extend it about 10° past Dubhe. There you will find M81 and, about 37 arcminutes due north of it, M82. The two fit in the same low-power field.

What you will see

In binoculars M82 is a faint, thin streak next to the brighter oval of M81. A 70–100 mm telescope shows a clear, bright sliver of light, several times longer than it is wide. In a 200 mm telescope M82 becomes one of the most detailed galaxies in the sky for its size: the bar of light looks patchy and uneven, and a dark dust lane cuts across its middle, splitting it into brighter sections. Its high surface brightness makes it a good galaxy for suburban skies. No filter is needed.

History

Johann Elert Bode discovered M82 together with M81 on December 31, 1774, describing a very pale, elongated nebulous patch. Pierre Méchain found both again in 1779, and Charles Messier added them to his catalog on February 9, 1781. Lord Rosse was the first to note the dark dust lanes across its center. In 1953 it was found to be a strong radio source, and it later became the prototype of starburst galaxies.