Ring Nebula M57 and its outer shell (Massimo Di Fusco)

Ring Nebula M57 and its outer shell

Messier 57 (also known as the Ring Nebula, M57 or NGC 6720) is a well-known planetary nebula located in the northern constellation Lyra. It has an apparent magnitude of 8.8 and lies at an approximate distance of 2300 light years from Earth. M57 lies south of Vega, the brightest star in Lyra and one of the stars that form the Summer Triangle, a prominent asterism found overhead in the summer sky. The nebula is easy to find as it is located roughly 40 percent of the distance from Sheliak (beta Lyrae) to Sulafat (gamma Lyrae).
The Ring Nebula was discovered by the French astronomer Antoine Darquier de Pellepoix in January 1779 and Charles Messier discovered the object independently on January 31, 1779. It is one of only four planetary nebulae listed in Messier’s catalogue, along with the Dumbbell Nebula (M27), the Little Dumbbell Nebula (M76), and the Owl Nebula (M97).

Planetary nebulae are formed when a dying red giant star expels its shell of ionized gas to form the nebula, while the star itself becomes a white dwarf, a dense stellar remnant roughly the size of the Earth. The central star of the Ring Nebula ejected its outer layers 6000 to 8000 years ago and they have since expanded over an area about 1.3 light years in radius. The nebula is expanding at a rate of about 1 arc second per century, which corresponds to a velocity of 20 to 30 km/s.

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Status	Advanced success
Started	...
Astrometry.net job	7311491
PixInsight job	2DWA0GNBKLHI4E7KQN2T5HI3IUMCUTAX
PixInsight queue size	n/a
PixInsight stage	TASK_LOG

RA (center)	18h53m33s.57
RA (top/left)	18h52m36s.10
RA (top/right)	18h54m32s.82
RA (bottom/right)	18h54m31s.20
RA (bottom/left)	18h52m34s.12

Dec (center)	+33°01′36″.5
Dec (top/left)	+32°52′11″.2
Dec (top/right)	+32°52′39″.3
Dec (bottom/right)	+33°11′00″.9
Dec (bottom/left)	+33°10′28″.4

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