M76, also known as the Little Dumbbell nebula, is a planetary nebula located in Perseus. At magnitude +10.1 and spanning 2.7 x 1.8 arc minutes, it's one of the faintest and smallest objects in the Messier 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, in 1891, suggested it was similar to the Ring Nebula (M57).
M76 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 - as it was suspected of consisting of two separate emission nebulae. The structure is now classed as a bipolar planetary nebula.
The Little Dumbbell Nebula is faint, but not difficult to locate as it's positioned just south of the prominent "W" asterism of Cassiopeia and 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, the planetary is circumpolar and therefore never sets. However from southern temperate latitudes, it's a difficult object that never climbs high above the northern horizon.
When viewed through small 80mm (3.1-inch) telescopes or large 20x80 binoculars, M76 appears as a faint, small and diffuse haze of light. It can be glimpsed with direct vision, but is better seen using averted vision and/or a nebula filter. Since faint, it's a difficult object at best appearing as an odd shape glow.
This planetary is a fine sight through small and medium size scopes. A 200mm (8-inch) reflector will show two almost equal sized lobes separated by dark lane. If seeing conditions permit, push up the magnitude to between 20x and 30x per inch of aperture to bring out subtle details. Of the two lobes, the southern one appears slightly brighter.
The Little Dumbbell Nebula is located approximately 2,500 light-years away. It has an actual 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|