NGC 6891

NGC 6891
Nebula
Planetary nebula
Hubble Space Telescope image of NGC 6891
Observation data: J2000.0 epoch
Right ascension20h 15m 08.84s[1]
Declination+12° 42′ 15.6″[1]
Distance12,400[2] ly
Apparent magnitude (V)12.51±0.23[3]
ConstellationDelphinus
DesignationsPN G054.1-12.1, PK 54-12.1, IRAS 20127+1233[1]

NGC 6891 is a bright, asymmetrical planetary nebula located in the northern constellation of Delphinus.[4][5][6] It was discovered on 22 September 1884, by Scottish astronomer Ralph Copeland, who observed it using visual spectroscopy with a 6.1-inch refractor at the Dun Echt Observatory in Aberdeen, Scotland.[7][1]

Characteristics

NGC 6891 displays a triple-shell structure, consisting of a bright inner nebula, an attached intermediate shell, and a detached outer halo.[8] High-resolution imaging reveals filaments, knots, and intricate details in the interior surrounding the central white dwarf star named HD 192563, along with at least two ellipsoidal shells oriented differently and a spherical outer halo expanding faster than the inner regions.[9] The bright optical regions have an apparent diameter of approximately 15 arcseconds.[7] The nebula shows evidence of multiple mass ejection episodes from its progenitor star.[8][4]

Observation

NGC 6891 has an apparent visual magnitude of around 10.5 to 12 and appears as a small, bluish disc in amateur telescopes of 6 inches (150 mm) aperture or larger, with the central star faintly visible under good conditions.[3] It lies near the celestial equator in Delphinus and is observable from both hemispheres.[6] The nebula has been imaged in detail by the Hubble Space Telescope, contributing to studies of planetary nebula structure, formation, evolution, and distance determination.[4]

Reference

  1. ^ a b c d "Simbad - Object view". simbad.cds.unistra.fr. Retrieved 2026-03-06.
  2. ^ Stanghellini, Letizia; Shaw, Richard A.; Villaver, Eva (2008). "The Magellanic Cloud Calibration of the Galactic Planetary Nebula Distance Scale". The Astrophysical Journal. 689 (1): 194–202. arXiv:0807.1129. doi:10.1086/592395. ISSN 0004-637X.
  3. ^ a b Høg, E.; Fabricius, C.; Makarov, V. V.; Urban, S.; Corbin, T.; Wycoff, G.; Bastian, U.; Schwekendiek, P.; Wicenec, A. (March 2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics. 355: L27–L30. ISSN 0004-6361.
  4. ^ a b c "Hubble's View of Planetary Nebula Reveals Complex Structure - NASA Science". 2021-11-29. Retrieved 2026-03-06.
  5. ^ Lazaro, Enrico de (2021-11-30). "Hubble Spots Beautiful Planetary Nebula: NGC 6891 | Sci.News". Sci.News: Breaking Science News. Retrieved 2026-03-06.
  6. ^ a b "NGC 6891 - Planetary Nebula in Delphinus | TheSkyLive". theskylive.com. Retrieved 2026-03-06.
  7. ^ a b "Planetary Nebula NGC 6891 | Deep⋆Sky Corner". www.deepskycorner.ch. Retrieved 2026-03-06.
  8. ^ a b Guerrero, Martín A.; Miranda, Luis F.; Manchado, Arturo; Vázquez, Roberto (2000). "The triple-shell structure and collimated outflows of the planetary nebula NGC 6891". Monthly Notices of the Royal Astronomical Society. 313 (1): 1–7. arXiv:astro-ph/9910378. doi:10.1046/j.1365-8711.2000.03159.x. ISSN 0035-8711.
  9. ^ Palen, Stacy; Balick, Bruce; Hajian, Arsen R.; Terzian, Yervant; Bond, Howard E.; Panagia, Nino (2002). "Hubble Space Telescope Expansion Parallaxes of the Planetary Nebulae NGC 6578, NGC 6884, NGC 6891, and IC 2448". The Astronomical Journal. 123 (5): 2666–2675. arXiv:astro-ph/0202003. doi:10.1086/339838. ISSN 0004-6256.
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