NGC 6781

NGC 6781, also known as the Snowglobe Nebula, is a planetary nebula located in the equatorial constellation of Aquila, about 2.5° east-northeast of the 5th magnitude star 19 Aquilae. It was discovered July 30, 1788 by the Anglo-German astronomer William Herschel. The nebula lies at a distance of 460 pc from the Sun. It has a visual magnitude of 11.4 and spans an angular size of 1.9 × 1.8 arcminutes.

The bipolar dust shell of this nebula is believed to be barrel-shaped and is being viewed from nearly pole-on. It has an outer angular radius of $61 arcsecond$; equivalent to a physical radius of 0.135 pc. The total mass of gas ejected as the central star passed through its last asymptotic giant branch (AGB) thermal pulse event is $0.41 solar mass$, while the estimated dust mass is $1.53 solar mass$.

The magnitude 16.88 central star of the planetary nebula is a white dwarf with a spectral type of DAO. It has an M-type co-moving companion at a projected separation of under $5,000 AU$. The white dwarf progenitor star had an estimated initial mass of $~2.5 solar mass$. It left the AGB and entered the cooling stage around 9,400 years ago.