| NGC 681 | |
| Appmag V: | 12 |
| Size V: | 2.70 × 1.8 arcmin |
| Constellation Name: | Cetus |
| Dist Ly: | ~66.5 million ly (20.39 ± 1.45 Mpc) |
| Epoch: | J2000 |
| H Radial V: | 1760.4 ± 6.6 km/s |
| Z: | 0.00587 ± 0.00002 |
| Type: | SAB(s)ab |
| Size: | ~29.07 kpc (diameter) |
| Mass Light Ratio: | 3.6 |
| Names: | [1] |
NGC 681 is an intermediate spiral galaxy in the constellation of Cetus, located approximately 66.5 million light-years from Earth.[2] [3] [4]
NGC 681 was discovered by the German-born British astronomer William Herschel on 28 November 1785 and was later also observed by William's son, John Herschel. John Louis Emil Dreyer, compiler of the first New General Catalogue of Nebulae and Clusters of Stars, described NGC 681 as being a "pretty faint, considerably large, round, small (faint) star 90 arcsec to [the] west" that becomes "gradually a little brighter [in the] middle".
NGC 681 shares many structural similarities with the Sombrero Galaxy, M104, although it is smaller, less luminous, and less massive. Its thin, dusty disc is seen almost perfectly edge-on and features a small, very bright nucleus in the center of a very pronounced bulge.[5] Distinctly unlike M104, NGC 681's disc contains many H II regions, where star formation is likely to be occurring.[6] The galaxy has a mass of M☉, a mass-to-light ratio of 3.6
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