M76 (short for
Messier
76) is also known as the Little Dumbbell
Nebula due to its shape appearing similar to
M27, The Dumbbell Nebula, when viewed visually through a
telescope. M76 is a
Planetary Nebula located in the direction of the
constellation
Perseus, the mythological Greek hero who slew Medusa the
Gorgon. M76 also bears the names of NGC 650 and NGC 651 in the
New General Catalog of Nebulae and Clusters of Stars, since it was
originally thought to be two objects (one for each loop
visible).
While M76 was cataloged as a Messier object by Charles Messier, it was
actually discovered by French astronomer
Pierre
Mechain, who became good friends with Messier and discovered
nearly a quarter of the objects in Messier’s catalog of over 100
early deep sky objects. Both astronomers were interested
primarily in finding comets, so they cataloged objects such as
M76 to avoid being mistaken as a comet.
This image shows
material ejected by its central star as it approaches its death.
M76 is somewhat unique in that it is a great example of a
reasonably bright planetary nebula that is bipolar, meaning it
has not just one but two stars which have and continue to eject
large amounts of material, leaving neutron or white dwarf stars
behind as visible in both the image and the enlarged inset*. The
brightest central star visible, HD 10346, is about
star magnitude 16 or about 10 thousand times fainter than
the faintest star visible with the human eye!
M76 is only about 2500 light years away, thereby it is about
1.25 light years across at its visual widest. Based on my
calculation of angle between the two visible central stars of
1.44 arc seconds (or 0.0004 degrees), the distance between the
two stars is 100 billion miles or about 6 light days! That is
about 30 times the distance to Pluto! Over the next few
thousands of years, the nebula will continue to expand until it
dissipates into deep space; its central stars will likewise fade
over time.
*Using a mouse, hover over the images above and below for
annotations, insets, and enlargements. The image below compares
M76 to its namesake big brother, M27, The Dumbbell Nebula! This
hover feature may be unavailable on smart phones.