Planetary nebula in the constellation Aquila
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 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 ; equivalent to a physical radius of . The total mass of gas ejected as the central star passed through its last asymptotic giant branch (AGB) thermal pulse event is , while the estimated dust mass is .
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 . The white dwarf progenitor star had an estimated initial mass of . It left the AGB and entered the cooling stage around 9,400 years ago.
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