NGC 281, Pacman Nebula

NGC 281
NGC 281: Pacman Nebula in Cassiopeia; 400 mm Cassegrain f/3 + STL11000M; 4.2h RGB SII H-Alpha OIII; Obwalden; © 2011 Eduard von Bergen

History

The nebula was discovered on November 16, 1881 by the American astronomer Edward Barnard with a 5 inch refractor and was later added to the «New General Catalogue» by Dreyer as NGC 281. Courtney Seligman suspects that Barnard had observed the same nebula again in 1890, but was in the Coordinates around half an hour in right ascension, which is why the same object was later included in the index catalog again as IC 11. [196, 277] At the specified position of IC 11 there is no nebula and the description «vF, L, triple * on np corner» (very faint, large, triple star on northwest corner) is practically identical to that of NGC 281.

The open star cluster IC 1590 was discovered on October 31, 1899 by the French astronomer Guillaume Bigourdan using the 12.4 inch refractor at the observatory in Paris. [277]

NGC 281
NGC 281: Pacman Nebula in Cassiopeia (north is left); 500 mm Cassegrain 3625 mm f/7.2; SBIG STL11K; 100+40+40+40 min LRGB; Bernese Highlands; © 2011 Radek Chromik

Physical Properties

The open star cluster IC 1590 near the center of the nebula is responsible for most of the high-energy radiation that makes the nebula glow. The brightest of the stars (HD 5005) has 7.7 mag and is a double star. SkySafari 6 Pro [149] specifies a distance of 3.9 arc seconds here.

For the nebula NGC 281 one finds at Simbad [145] a distance of 3.1 kpc (10'100 light years) and for the small star cluster IC 1590 a distance of 2'384 kpc (7776 light years).

«Revised New General Catalogue and Index Catalogue», «Historically Corrected New General Catalogue», Dr. Wolfgang Steinicke, 2021 [277]
NameRADecTypeBmagVmagDimDreyer DescriptionIdentification
NGC 281 00 52 53.8+56 37 30EN35.00 × 30.0F, vL, dif, S triple * on np edgeIC 11, LBN 616, in OCL 313
IC 11 00 52 53.8+56 37 30EN35.00 × 30.0vF, L, triple * on np cornerNGC 281, LBN 616, in OCL 313
IC 1590 00 52 48.0+56 37 54OCL (OCL+EN)Cl, vL, st sc, 281 fin N 281

Finder Chart

The Pacman Nebula is located under the «W» of the Cassiopeia constellation. The constellation is circumpolar, but it is highest at night from July to January. Form an equilateral triangle with the two stars Shedar (α Cassiopeiae) and Achird (η Cassiopeiae).

Chart NGC 281
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

762 mm aperture: NGC 281, also known as «Pac Man» due to its appearance, is dominated by the black snout, which is already squeezing into the picture far from the side. In the brighter part of the nebula, similar to an aquarium on color photos, the larger granule can be seen on the romboid of 4 faint stars. — 30" f/3.3 Slipstream Dobsonian, Hasliberg Reuti, 3. 3. 2022, Eduard von Bergen

References

145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)