NGC 973 is a giant[3]spiral galaxy located in the constellationTriangulum. It is located at a distance of circa 200 millionlight-years from Earth, which, given its apparent dimensions, means that NGC 973 is about 230,000 light years across. It was discovered byLewis Swift on October 30, 1885.[4]
NGC 973 is seen edge-on, with an inclination of nearly 90°.[5] Itsbulge is shaped like a box or peanut. The subtraction of axisymmetric components from the profile of the galaxy showed that its bulge has an X-like morphology, which indicates the presence of abar.[6] A prominent dust lane runs across the galaxy.[7]
The galaxy kinematics revealed that the northeast side is the approaching one and the southwest is receding. The disk appears flat, without warps. The totalhydrogen mass of the galaxy is estimated to be about9×109M☉,[8] and the totaldust mass is estimated to be1.4×108M☉, with clumpy distribution.[5] Faint emission from gas lying outside the plane of the galaxy was detected inH-alpha, correlated with the galactic disk and halo.[9]
The nucleus of NGC 973 appears to beactive based on its emission. It is categorised as a type 2Seyfert galaxy.[10][11] The most accepted theory for the energy source of active galactic nuclei is the presence of anaccretion disk around asupermassive black hole.
NGC 973 forms a pair with IC 1815, which lies 4.6 arcminutes to the south.[15] A smallsatellite was discovered in HI imaging near the northeast edge of the disk of NGC 973, with no optical counterpart.[8]
^abXilouris, E. M.; Kylafis, N. D.; Papamastorakis, J.; Paleologou, E. V.; Haerendel, G. (1 September 1997). "The distribution of stars and dust in spiral galaxies: the edge-on spiral UGC 2048".Astronomy and Astrophysics.325:135–143.Bibcode:1997A&A...325..135X.ISSN0004-6361.
^Guthrie, B. N. G. (1 May 1992). "Axial ratios of edge-on spirals".Astronomy and Astrophysics Supplement Series.93:255–270.Bibcode:1992A&AS...93..255G.ISSN0365-0138.
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