|M81 (NGC 3031)||Spiral Galaxy||09h 55m 33s||+69° 03′ 55″||Ursa Major||6.77||22 x 11 arcmins|
|M82 (NGC 3034), the Cigar Galaxy||Spiral Galaxy||09h 55m 52s||+69° 40′ 47″||Ursa Major||8.02||11 x 5.1 arcmins|
These two galaxies were discovered by Johann Bode in 1774. Describing what he saw as a ‘nebulous patch’ led to their becoming known, jointly, as Bode’s Nebula. Messier had them reported to him by Pierre Machin, who discovered them independently of Bode in 1779. Messier included them in his eponymous catalog from 1781.
This bright pair of galaxies is circumpolar for most of us in the northern hemisphere, meaning it never sets below the horizon, but spring is a particularly great time to take a look of these two distant worlds as they ride high in the late evening sky. Both galaxies fit comfortably inside the same 1° field of view, which makes for particularly lovely viewing. Together, they are bright enough to be spied in binoculars and small telescopes under dark skies.
M81 is the larger of the two worlds. This one is ‘close by’ at just 12 million light-years distant and is the largest galaxy in the M81 group. The M81 group is a cluster of 34 galaxies, and neighbor to our own Local Group. Recently, M81 shot to fame for being home to the first supermassive black hole to ever be imaged, its mass is equivalent to 70 million suns.
The larger of the two galaxies is about 70,000 light-years across and is more massive than the Milky Way at 250 billion suns. M82, although much smaller, is five times brighter than the Milky Way with a center 100 times more luminous.
Hundreds of millions of years ago, M81 and M82 had a close encounter which dramatically deformed M82 and left an impact in the spiral patterns of M81. It also caused M82 to dramatically increase the number of new stars being born in its arms. Today, the two galaxies are as close as 130,000 light-years apart.
These galaxies are bright and located in one of the most recognizable areas of the night sky. Even so, honing in on their precise location can be a little bit tricky. The charts below, all from SkySafari 6, show you where to find M81 and M82, shown green.
This first chart shows you where the two galaxies are located. This is the view at 11pm in the middle of June, looking northwest. Stars are shown to magnitude 5.0.
Note the Big Dipper (Plough) asterism that is shown in orange. This is the easiest part of Ursa Major to identify.
We now zoom in to show stars to magnitude 7.0. We now need to find the star d Ursae Majoris (24 Ursae Majoris) to lead us to our prey. Shining at magnitude 4.55, d Ursae Majoris (d UMa) is easy enough to locate with the naked eye. It is 6° north of h Ursa Majoris and forms the base of a triangle with the bright star Dubhe at its peak.
Once you’d found d UMa, it is easy to hop 2° east from there to the galaxies. It’s easiest to hop first to HR 3838, a magnitude 5.7 star, and then onwards to M81. This is demonstrated in the final finder chart below, that shows stars to magnitude 9.0.
The following view shows the scene in a 1° field of view with an exaggerated brightness image of the two galaxies, i.e. don’t expect them to be this bright in reality. Stars are shown to magnitude 11.0.
Now you have these relatively close galaxies in your eyepiece, what should you expect to see?
The following views will help you find M81 and M82 in different telescope types by presenting the images as your telescope will show them. The first image is with a black sky and white stars, the second picture is the same image but presented in inverse monochrome. Black stars on a white background is often easier to use at the telescope. Each image can be clicked on for a full-screen version.
Upright View – This is what your eyes see unaided and through a reflex or red-dot finderscope
Upside-down view – This is what reflectors and magnifying finders show, and refractors / Cassegrains without a star diagonal
Mirrored View – Refractors and Cassegrain models with a star diagonal show this view
This is the best example of seeing two galaxies in a single eyepiece view in the northern hemisphere. Together, these galaxies are bright enough (if your sky is dark enough) to be seen in a magnifying finderscope and are comfortably visible in binoculars.
M81 is the brighter and larger of the pair and presents itself as a large oval with a bright center. In contrast, M82, as its informal name suggests, is a thin cigar shaped apparition with an even brightness across its body but with a definite blotchy appearance.
Staring at M82 forces you to have averted vision with respect to M81, and it is using this false looking that shows M81 to be clearly the larger of the two subjects.
These two accept higher magnifications, and dialling up your eyepiece choice helps to reveal the halo glow surrounding M81. These are its large spiral arms, which are a tough challenge to see with any detail. Larger telescopes coupled with higher magnification expose more texture in M81’s shroud of stars and you may now see more detail in the arms. Whatever size of telescope you own, see if you can identify darker patches within its bright appearance.
More magnification shows that the cigar of M82 is definitely patchy, especially along its western end. It is an intricate mix of brighter, sharper patches of starlight and darker, fainter breaks between them.
This is a view that I can enjoy for a long time. Relax into it, use averted vision on both galaxies, and don’t be afraid to test magnification on each to see what results you get. Take note of the shapes you see and the intricate balance between ghostly grey, brighter white, and darker night.
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Each of the star maps above is reproduced as a pdf below. Each star map has a number in [square brackets] beneath it which corresponds to the file number below. If you want image [M81-1], for example, click the ‘download’ button next to it below and you’ll be able to open it as a printable pdf.