Nicknamed the "Pacman Nebula," NGC 281 is classified as an emission nebula. An emission nebula is a cloud of high temperature gasses energized by a nearby star's radiation, causing the cloud to glow. In the case of Pacman, the energizing star is actually several stars in the open star cluster IC 1590, which is in the center of the nebula. NGC 281 and IC 1590 are about 10,000 light years away, span about 80 light years across, and are located in the constellation Cassiopia. In 1883, astronomer E.E Barnard discovered the nebula refuring to it as, "a large faint nebula, very diffused."
Only the center of Pacman is shown about due to its enormous size--be sure to click on the image to see the entire nebula in all of its beauty. To capture the entire nebula, we created a two-by-two mosaic image, using an H alpha filter. The H alpha filter gave us a monocrome image. We then chose a color palette that emphesized red, since H alpha light is red light. This allowed us to portray the red glow of Hydrogen, a common element of emission nebulae. Therefore, this image shows NGC 281 as it would naturally appear.
IC 1590 in this photograph shows up as one star slightly to the upper left to the center but it is actually 3 very young, very bright stars. These stars' emission of ultraviolet light is what energizes the cloud, NGC 281, and allows it to glow while the high amount hydrogen gives it the red color. Pacman's ribbon-like waves comes from the emission of ultraviolet light as well. The emission creates powerful solar winds, which blow the cloud about. Pacman is about 0.46º degrees of arc across.
EarthSky. "Nebula NGC 281 Dazzles in the Infrared." EarthSky. <http://earthsky.org/space/nebula-ngc-281-dazzles-in-the-infrared>.
Anderson Janet and Watzke, Megan. "The Pacman Nebula." NASA. <http://www.nasa.gov/mission_pages/chandra/multimedia/pacman.html>.
Frommert, Hartmut and Kronberg, Christine. "NGC 7293." Students for the Exploration and Development of Space. <http://www.seds.org/MESSIER/xtra/ngc/n7293.html>
Smith, Graham. "Two-in-One: The dazzling Pac-Man Nebula powered by an open cluster of stars." MailOnline. <http://www.dailymail.co.uk/sciencetech/article-2031410/NGC-281-The-dazzling-Pac-Man-Nebula-powered-open-cluster-stars.html>
|Right Ascension (J2000)||00:54:13.5, 00:51:44.5|
|Declination (J2000)||+56:44:04, +56:30:34|
|Filters used||H alpha|
|Exposure time per filter||H alpha (300)s|
|Date observed||November 14 2011|