NGC 6781
Template:Short description Template:Infobox nebula
NGC 6781, also known as the Snowglobe Nebula,[1] is a planetary nebula located in the equatorial constellation of Aquila, about 2.5° east-northeast of the 5th magnitude star 19 Aquilae.[2] It was discovered July 30, 1788 by the Anglo-German astronomer William Herschel.[3] The nebula lies at a distance of Template:Cvt from the Sun.[4] It has a visual magnitude of 11.4 and spans an angular size of 1.9 × 1.8 arcminutes.[2]
The bipolar dust shell of this nebula is believed to be barrel-shaped and is being viewed from nearly pole-on.[5] It has an outer angular radius of Script error: No such module "val".; equivalent to a physical radius of Template:Cvt. The total mass of gas ejected as the central star passed through its last asymptotic giant branch (AGB) thermal pulse event is Script error: No such module "val"., while the estimated dust mass is Script error: No such module "val"..[4]
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 Script error: No such module "val"..[6] The white dwarf progenitor star had an estimated initial mass of Script error: No such module "val".. It left the AGB and entered the cooling stage around 9,400 years ago.[4]
References
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