Ursa Major is best known for the Big Dipper, but the Great Bear also contains some of the finest deep-sky objects in the northern sky. Its seven Messier objects include several bright galaxies and one of the best-known planetary nebulae.
For observers at mid-northern latitudes, Ursa Major is particularly convenient because much of the constellation remains visible throughout the year. The Big Dipper also provides familiar stars that can be used as starting points for finding several of the objects below.
Bode’s Galaxy (M81, NGC 3031)
- Coordinates: RA 09h 55m 33s | Dec. +69° 04′
- Magnitude: +6.9
- Distance: About 11.6 million light-years
- Type: Spiral galaxy
Discovered by German astronomer Johann Elert Bode in 1774, M81 is one of the brightest galaxies visible from Earth. It is the dominant member of the M81 Group and a classic example of a grand-design spiral galaxy, with prominent spiral arms surrounding a bright central bulge.
M81 contains a supermassive black hole of about 70 million solar masses at its center. It has also interacted gravitationally with nearby M82 and NGC 3077. These encounters have disturbed gas within the group and helped trigger episodes of star formation.
Visibility: Look for M81 roughly 10 degrees northwest of Dubhe (Alpha Ursae Majoris). Under dark skies it can be detected with binoculars as a faint patch of light, while a small telescope reveals its brighter central region. M81 and M82 can often be seen together in the same low-power field of view.
Cigar Galaxy (M82, NGC 3034)
- Coordinates: RA 09h 55m 52s | Dec. +69° 41′
- Magnitude: +8.4
- Distance: About 12 million light-years
- Type: Starburst galaxy
Close to M81 in the sky lies the Cigar Galaxy, or M82. Seen nearly edge-on from Earth, its elongated appearance gives the galaxy its familiar nickname.
M82 is especially notable for the intense star formation taking place near its center. Gravitational interaction with M81 has disturbed the galaxy and helped drive gas toward its central regions, producing a powerful starburst. Stars are currently forming in M82’s center at a much higher rate than across the Milky Way as a whole.
Visibility: M82 is an excellent target for small and medium-sized telescopes and is easiest to locate by first finding M81. At low magnification the two galaxies make an impressive pair, with the rounded glow of M81 contrasting with the narrow, elongated form of M82.
Pinwheel Galaxy (M101, NGC 5457)
- Coordinates: RA 14h 03m 13s | Dec. +54° 21′
- Magnitude: +7.9
- Distance: About 25 million light-years
- Diameter: About 170,000 light-years
- Type: Face-on spiral galaxy
Discovered by French astronomer Pierre Méchain in 1781, M101 is one of the finest examples of a face-on spiral galaxy. Its enormous disk spans about 170,000 light-years and is estimated to contain at least one trillion stars.
The Pinwheel Galaxy is particularly rich in large star-forming regions scattered along its spiral arms. Several are so prominent that they have their own NGC designations, including NGC 5461, NGC 5462 and NGC 5471. M101’s noticeably asymmetric structure is thought to have been shaped in part by gravitational interactions with neighboring galaxies.
Visibility: Despite its integrated magnitude of about +7.9, M101 can be surprisingly difficult to see because its light is spread across a large area of sky. Dark, transparent skies are more important than high magnification. Under good conditions it can be detected in binoculars and small telescopes, while larger apertures begin to reveal more of its spiral structure.
The Owl Nebula (M97, NGC 3587)
- Coordinates: RA 11h 14m 48s | Dec. +55° 01′
- Magnitude: +9.9
- Distance: About 2,000 light-years
- Type: Planetary nebula
Discovered by Pierre Méchain in 1781, the Owl Nebula is a planetary nebula formed from material expelled by a dying star. Its familiar nickname dates from an 1848 drawing by William Parsons, the 3rd Earl of Rosse, who thought that two darker regions within the nebula resembled the eyes of an owl.
The nebula is roughly 2,000 light-years from Earth and is thought to be several thousand years old. Its expanding shells of gas were expelled as its progenitor star evolved late in its life, eventually leaving behind the hot white dwarf at the nebula’s center.
Visibility: Look for M97 about 2.5 degrees southeast of Merak (Beta Ursae Majoris), the star at the southwestern corner of the Big Dipper’s bowl. The nebula appears as a small, faint disk in modest telescopes. Under dark skies, larger instruments can begin to reveal the darker regions responsible for its owl-like appearance.
Other Deep-Sky Objects in Ursa Major
Ursa Major contains many more galaxies beyond M81, M82 and M101. Two particularly worthwhile Messier targets are M108, an edge-on spiral galaxy located close to the Owl Nebula, and M109, a barred spiral galaxy near Phecda in the Big Dipper’s bowl.
Together, these objects make Ursa Major much more than a constellation used to find Polaris. Its familiar stars provide convenient landmarks for exploring some of the northern sky’s most accessible galaxies and planetary nebulae.