NGC 6781 explained

Type:Planetary
Dist Pc:460
Appmag V:11.4

NGC 6781, also known as the Snowglobe Nebula,[1] is a planetary nebula located in the equatorial constellation of Aquila, about 2.5Ā° 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 .

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.

Notes and References

  1. Book: Stoyan, Ronald. Schurig. Stephan. interstellarum Deep Sky Atlas. Cambridge University Press; Oculum-Verlag GmbH. Erlangen. 2014. 978-1-107-50338-0. 920437579.