NGC 281, IC 11 or Sh2-184 is a bright emission nebula and part of an H II region in the northern constellation of Cassiopeia and is part of the Milky Way's Perseus Spiral Arm. This 20×30 arcmin sized nebulosity is also associated with open cluster IC 1590, several Bok globules and the multiple star, B 1. It collectively forms Sh2-184, spanning over a larger area of 40 arcmin. A recent distance from radio parallaxes of water masers at 22 GHz made during 2014 is estimated it lies 2.82±0.20 kpc. (9200 ly.) from us. Colloquially, NGC 281 is also known as the Pacman Nebula for its resemblance to the video game character.
|H II region|
|Observation data: J2000.0 epoch|
|Right ascension||00h 52m 59.3s|
|Declination||+56° 37′ 19″|
|Distance||9500 ly (2900 pc)|
|Apparent dimensions (V)||35′|
|Notable features||open cluster IC 1590, the multiple star B 1, and several Bok globules|
|Designations||IC 11, Sh2-184, Sharpless 184, LBN 616, LBN 123.17-06.28, Pacman Nebula|
Edward Emerson Barnard discovered the nebula in August 1883, describing it as "a large faint nebula, very diffuse." Multiple star 'B 1' or β 1 was later discovered by S. W. Burnham, whose bright component is identified as the highly luminous O6 spectral class star, HD 5005 or HIP 4121. It consists of an 8th-magnitude primary with four companions at distances between 1.4 and 15.7 arcsec. There has been no appreciable change in this quintuple system since the first measures were made in 1875.