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Anne’s Image of the Day: Spiral Galaxy NGC 2841
read more at Anne’s Astronomy News http://annesastronomynews.com/
July 19, 2013
NGC 2841, a spiral galaxy in Ursa Major
Image Credit & Copyright: Adam Block/Mount Lemmon SkyCenter/University of Arizona
(http://skycenter.arizona.edu/gallery/Galaxies/NGC2841)
NGC 2841 is a giant unbarred spiral galaxy of more than 130.000 light-years across, located about 46 million light-years away in the northern constellation of Ursa Major (the Great Bear), while it is receding from us at approximately 638 kilometers per second. It was discovered on March 9, 1788 by the German-British astronomer William Herschel.
It is a prototypical flocculent spiral galaxy, a type of spiral galaxy whose arms are patchy and discontinuous. A bright, yellow nucleus of starlight marks the galaxy’s center, but the western part of this island universe is partly obscured by the galaxy’s halo, reducing the contrast in this area. There seems to be a faint tidal stream out from the north-west of the galaxy.
The patchy but symmetrical, tightly wound spiral arms contain many star clusters with large populations of young blue stars, and a population of whitish middle-aged stars. Spiraling outward from the center are dark dust lanes that are silhouetted against the arms. This galaxy has had a history of supernovae explosions within it, the most recent going off in 1999.
NGC 2841 contains only a few pinkish emission nebulae indicative of new star birth. It is likely that the radiation and supersonic winds from fiery, super-hot, young blue stars cleared out the remaining gas (which glows pink), and hence shut down further star formation in the regions in which they were born. The galaxy currently has a relatively low star formation rate compared to other spirals that are ablaze with emission nebulae.
The rapid outflows of gas from giant stars, and supernova explosions in the disk of a galaxy create huge shells or bubbles of hot gas that expand rapidly and rise above the disk like plumes of smoke from a chimney, shown in a X-ray image of NGC 2841 (not visible in this image). The registration provides direct evidence for this process, which pumps energy into the thin gaseous halo that surrounds the galaxy.
This image was taken on March 6th, 2011 with an SBIG STX16803 CCD Camera on the 32-inch Schulman Telescope (RCOS) at the Mount Lemmon SkyCenter.
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