NGC 281 — Emission Nebula in Cassiopeia

NGC 281 is a large emission nebula in Cassiopeia, about 9,500 light-years away, popularly known as the Pacman Nebula because the dark dust intrusion on its eastern side resembles the open mouth of the arcade-game character. The nebula spans about 35 arcminutes — larger than the full Moon — and is ionized by the young open cluster IC 1590 embedded near its centre. Several Bok globules — small, dense clumps of cold gas where new stars are forming — silhouette themselves against the bright background, making NGC 281 one of the most often-imaged nearby star-forming regions.

Visually a challenging but rewarding target. From a dark site, a 4-inch at low power with a UHC or narrowband filter reveals the brightest portions of the nebula as a faint round glow. An 8-inch with the same filter brings out the Pacman shape, with the dark intrusion clearly visible against the nebulous background. The cluster IC 1590 (about magnitude 7.4) at the centre adds visual interest and is easy in any scope. Star-hop from Schedar (Alpha Cassiopeiae) about 1.7 degrees east. Best observed September through February.

Discovered by Edward Emerson Barnard in 1883 with the 6-inch Cooke refractor at the Vanderbilt Observatory. The Pacman nickname is a 1970s/80s amateur invention. The Bok globules in the nebula were among the first targets identified by Bart Bok in his 1947 paper introducing the concept of small dense clouds as the seeds of star formation.