APOD 3.5

NGC 4013, only about 50 million light-years away, can be seen in the constellation Ursa Major, and was originally thought to be a distant island universe. This spiral galaxy is especially known for its flattened disk shape and large amount of central stars with many dust lines. This image identifies a previously unknown object associated with NGC 4013, which is the enormous, faint loop which extends up and to the left, and is a mere 80 light-years from the galaxy's center. With further investigation, it appears that this faint loop is a stream of stars, originally belonging to another galaxy which was probably torn apart by gravitational tides as it merged with the larger spiral. Many astronomers believe this newly discovered tidal stream may explain the warped distribution of neutral hydrogen gas which has been seen in radio images of NGC 4013 and may even help explain the formation of our own Milky Way galaxy. This image is pretty amazing looking, and it is pretty cool to see the faint ring which is the stream of stars. To me, the stream of stars looks more like a stream of dust, but maybe that's just because this star stream is over 80 light-years away from a galaxy that is over 50 light-years away, which we all known is pretty far.