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Anne’s Picture of the Day: Spiral Galaxy NGC 4013
read more at Anne’s Astronomy News http://annesastronomynews.com/
May 5, 2013
NGC 4013, an edge-on spiral galaxy in Ursa Major
Image Credit & Copyright: R. Jay GaBany, Cosmotography (http://www.cosmotography.com)
NGC 4013 is a barred spiral galaxy of some 100 thousand light-years across, located about 55 million light-years away from Earth in the constellation of Ursa Major (also known as the Big Dipper), while it is receding from us at approximately 831 kilometers per second.
All spiral galaxies (including our own Milky Way galaxy) are highly flattened disk-like structures that resemble giant pancakes. The disk of this edge-on galaxy shows a distinct peanut-shaped bulge of stars that is consistent with a stellar bar seen perpendicular to the line of sight.
Most of its dust lanes lie in the galaxy’s plane, forming the dark band, about 500 light-years thick. This dark band, that absorbs the light of background stars, appears to cut the galaxy in two. By studying the color and the amount of light absorbed by these distant clouds in NGC 4013, astronomers can estimate the amount of matter in them.
These dark dust lanes are believed to be where new stars are formed. Later, when the dust disperses, the young stars become visible as clusters of blue stars. NGC 4013 shows several examples of these stellar nurseries, lying in front of the dark band along the galaxy’s equator.
NGC 4013 was long considered an isolated island universe. But, this deep color image also reveals a faint looping tidal stream of stars extending (above and toward the left) over 80 thousand light-years from the center of NGC 4013. The significantly redder color of the stream material compared to the outer parts of the disk suggests that this loop did not originate from the disk itself, but rather is the tidal stream of a dwarf galaxy being torn apart by tidal forces as it merged with NGC 4013.
This tidal stream also explains a warped distribution of neutral hydrogen gas seen in radio images of NGC 4013..
On December 30, 1989, the supernova SN 1989Z was discovered in NGC 4013.
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Source: http://annesastronomynews.com/annes-picture-of-the-day-spiral-galaxy-ngc-4013/
