M76 or "The Little Dumbbell Nebula" is a planetary nebula located in Perseus. At magnitude +10.1 and spanning 2.7 x 1.8 arc minutes, its one of the faintest and smallest objects in Messier's catalogue. The nebula was discovered by Pierre Méchain on September 5, 1780 and first recognised as a planetary nebula by American astronomer Heber Doust Curtis in 1918. However, Isaac Roberts suggested it was similar to M57 (Ring Nebula) in 1891.
M76 itself looks like a miniature version of the famous Dumbbell Nebula (M27) in Vulpecula, from which it derives its name. Interestingly, it was assigned two NGC numbers - NGC 650 and 651 - since wrongly suspected of consisting of two separate emission nebulae. The structure is now classed as a bipolar planetary nebula.
The Little Dumbbell Nebula maybe faint but not difficult to locate; it's positioned just south of the prominent "W" asterism of Cassiopeia and only a degree north-northwest of Phi Persei (φ Per - mag. +4.0). It's best seen from the Northern Hemisphere during the months of October, November and December. From latitudes 40N or more it's circumpolar and hence never sets. However from southern temperate latitudes, M76 is a difficult object that never climbs high above the northern horizon.
When viewed through a small 80mm (3.1-inch) telescope or large 20x80 binoculars, M76 appears faint, small and diffuse. It can be glimpsed with direct vision but better seen when using averted vision and/or a nebula filter. Since faint it's a difficult object at best appearing as an odd shape glow.
The nebula is a fine sight through small and medium size scopes. A 200mm (8-inch) telescope will show the two almost equal sized lobes separated by dark lane. If conditions permit, push up the magnitude to between 20x and 30x per inch of aperture to bring out more subtle details. Of the two lobes, the southern one appears slightly brighter.
The Little Dumbbell Nebula is located approx. 2,500 light-years from Earth, which corresponds to a spatial diameter of about 2 light-years.
M76 Data Table
|Name||Little Dumbbell Nebula|
|Object Type||Planetary nebula|
|RA (J2000)||01h 42m 18s|
|DEC (J2000)||51d 34m 16s|
|Apparent Size (arc mins)||2.7 x 1.8|
|Notable Feature||Considered to be one of the most difficult objects to see in Messier's list|