Planetary Nebula NGC 6891

NGC 6891
NGC 6891: Image taken with Hubble Space Telescope. © ESA/Hubble & NASA, postprocessing Judy Schmidt [165]


This planetary nebula was discovered on 22 September 1884 by the Scottish astronomer Ralph Copeland using visual spectroscopy with a 6.1 inch refractor at Earl of Crawford's Observatory, Dun Echt, Aberdeen. [277]

Physical Properties

NGC 6891 is a triple-shell planetary nebula: It shows a bright central nebula which is surrounded by an attached shell and a detached outer halo. The inner and intermediate shells are ellipsoids with similar major to minor axial ratios, but different spatial orientations. The kinematical age of the intermediate shell is 4800 years and of the halo is 28'000 years. An outflow is observed to protrude from the tips of the major axis of the inner nebula and impact on the outer edge of the intermediate shell. The mass of the central white dwarf star is estimated to 0.75 times the mass of our Sun. Its surface temperature is 50'000 K. The distance to Earth is 3.8 kpc. [586]

«Strasbourg-ESO Catalogue of Galactic Planetary Nebulae» Acker et al., 1992 [141]
DesignationsPN G054.1-12.1: NGC 6891, PK 54-12.1, ARO 37, VV 253, VV' 529
Right Ascension (J2000.0)20h 15m 09s
Declination (J2000.0)+12° 42' 07"
Dimensions 15." (optical)
Distance 0.83 kpc
Radial Velocity+42.4 km/s ± 1.0 km/s
Expansion Velocity 7.0 km/s (O-III)
C-Star DesignationsAG82 403, BD +12 4266, EM* CDS 1140, GCRV 12622, HD 192563
C-Star Magnitude12.30 mag (B filter), 12.42 mag (V filter)
C-Star Spectral TypeOf (H)
DiscovererCOPELAND 1884

Finder Chart

The planetary nebula NGC 6891 is not easy to find, as it is located in a relatively star-poor area between Delphinus and Aquila befindet. The best observation time is from May to October.

Finder Chart Planetary Nebula NGC 6891
Planetary Nebula NGC 6891 in constellation Delphinus. Charts created using SkySafari 6 Pro and STScI Digitized Sky Survey. Limiting magnitudes: Constellation chart ~6.5 mag, DSS2 close-ups ~20 mag. [149, 160]

Visual Observation

400 mm Aperture: In the 21 mm Tele Vue Ethos eyepiece, the figure shown in the 1° close-up doesn't immediately catch one's eye, and locating it isn't quite easy. With some patience and multiple repositioning of the Telrad, it is possible to eventually find the small, slightly bluish round speck. In the 9 mm Nagler eyepiece, the planetary nebula becomes somewhat clearer, and a central star can be discerned. However, it was not possible to observe that the inner part should be brighter. — 400 mm f/4.5 Taurus Dobsonian, Glaubenberg, 11. 10. 2023, SQM 20.9, Bernd Nies

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