NGC 281

NGC 281

Published: November 21, 2007, 12:00 am
Updated: March 28, 2009, 9:59 pm
Lead Author: Bryan Mendez
Topics: Nebulae Stars

NGC 281 Data

Object Name: NGC 281, IC 0011, Pac Man Nebula, IC 1590

Object Type: Nebula, Star Cluster, Open Cluster, HII Region

Location: RA: 00h 52m 59.35s Dec: +56d 37m 18.8s (J2000.0; Galactic Coordinates: l =13.247, b = 56.622). In the constellation Cassiopeia. Most easily visible in the sky of the northern hemisphere October through December.

Object Distance: 9,500 ly (2.9 kiloparsecs, Hubblesite)

Object Size: 48 Arcmin (DSS image), 132 ly (40.5 pc, DSS image)

Object Brightness: apparent visual magnitude = 7 (Open Cluster, SEDS), absolute visual magnitude = ()

Object Description: NGC 281 is a nebula located in the Perseus spiral arm of the Milky Way Galaxy. Its appearance is reminiscent of the video game icon from the 1980s, Pac-Man, so astronomers have recently informally nicknamed it the Pac-Man Nebula.

NGC 281. Click on image for un-cropped/full-size version. NGC 281. Click on image for un-cropped/full-size version.

NGC 281 - Sometimes referred to casually as the Pacman Nebula, it is an H II region in the constellation of Cassiopeia and part of the Perseus Spiral Arm. It includes or is near the open cluster IC 1590, the double star HD 5005, and several Bok globules. It is visible in amateur telescopes from dark sky locations. (Source: Wikipedia. Credit: Hunter Wilson.)

In the center of the nebula is an open cluster of stars, called IC 1590. This cluster of stars is easily visible in a small telescope with faint nebulosity. Longer exposure times are needed to bring the nebula into full view.

The major features of the Pac-Man Nebula are the bright blue stars in its center, a dark lane forming its “mouth,” and several dark spots across its expanse. The natural color of the nebula is red.

The Pac-Man Nebula is a region of active star formation in the Milky Way Galaxy. It is a region in the Galaxy where the interstellar medium is gathered into a cloud of higher than average density. Here the hydrogen gas within the cloud is being ionized by strong ultraviolet radiation from the hot, young stars that have newly formed within the cloud itself. Such places are called HII Regions by astronomers (where the HII refers to the ionized state of hydrogen in the cloud). The young stars in the Pac-Man Nebula form an Open Cluster, IC 1590, which have only formed within the last few million years.

The hydrogen gas in the nebula that is being ionized by the young stars emits the red light that gives the nebula its color. The dark lanes are regions of dense dust and cool gas (mostly molecular hydrogen). As parts of these dark lanes become more dense, they will likely give rise to future star formation.

The dark spots across the nebula are called “Bok globules” by astronomers. These are areas of the coldest and densest gas and dust. They are dense enough to block the emission of light from the parts of the nebula behind it. Inside these globules new stars are able to form. Stars form when parts of the interstellar medium, such as the Pac-Man Nebula, become dense enough for gravity to take hold and pull matter together. Bok globules are like cocoons for stars. The dense gas and dust in the globule protect newly forming stars from being disrupted by the radiation and winds of the hot young stars that have already formed in the region. When the news stars inside become hot enough they will start blowing winds and sending out enough radiation to evaporate the globules. Sometimes Bok globules can be disrupted by the winds and radiation from nearby, young, hot stars, like those in IC 1590, before the globules have a chance to trigger star formation in their cores. This may be the case for the most prominent globules at the center of NGC 281.

Related Topics: Nebulae, Star Clusters, Star Formation

External Links

National Virtual Observatory - Hubble Space Telescope PR Images: VO DataScope Query (Searched "NGC 281") Returned these HST PR SIA resources:

These opaque, dark knots of gas and dust are called Bok globules, and they are absorbing light in the center of the nearby emission nebula and star-forming region, NGC 281. The globules are named after astronomer Bart Bok, who proposed their existence in the 1940's.
- http://imgsrc.hubblesite.org/hu/db/2006/13/images/a/formats/full_tif.tif (~25 MB)
See also: HubbleSite Gallery.

This wide-field view of the star-forming region NGC 281 in the constellation Cassiopeia was taken with the WIYN 0.9-meter telescope at Kitt Peak National Observatory near Tucson, AZ.
- http://imgsrc.hubblesite.org/hu/db/2006/13/images/b/formats/full_tif.tif (~76 MB)
See also: HubbleSite NewsCenter.
 

The National Virtual Observatory (NVO) is the US-based Virtual Observatory project that is collaborating with the International Virtual Observatory Alliance (IVOA) to make it possible for astronomical researchers to find, retrieve, and analyze astronomical data from ground- and space-based telescopes worldwide. The origin of the NVO can be traced to the establishment in the early 1990s of wavelength-oriented science archive centers for NASA mission datasets.
For more information, visit the NVO Homepage and NVO FAQs.

More Resources:

Preview Image

This wide-field view of the star-forming region NGC 281 in the constellation Cassiopeia was taken with the WIYN 0.9-meter telescope at Kitt Peak National Observatory near Tucson, AZ. (Source: HubbleSite NewsCenter.)

Citation

Méndez, Bryan, Ph.D. (Contributing Author); Bernard Haisch (Topic Editor). 2008. "NGC 281." In: Encyclopedia of the Cosmos. Eds. Bernard Haisch and Joakim F. Lindblom (Redwood City, CA: Digital Universe Foundation). [First published November 21, 2007].
<http://www.cosmosportal.org/articles/view/135900/>

 

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