Discovered by William Herschel on February 22, 1787
NGC 3115 is one of two galaxies that have been given the common name of the Spindle Galaxy. The other is M102 (NGC 5866). NGC 3115 is classed as a lenticular galaxy. Lenticulars are disk shaped with a central bulge but without the typical spiral arms that we usually associate with flat disk shaped galaxies such as our own Milky Way. When viewed from an edge on perspective, as is the case with NGC 3115, they display a lens shape and thus the classification lenticular. NGC 3115 is seemingly unspectacular when viewed in most amateur telescopes but scientifically it is very interesting. It was one of the first galaxies discovered to have an extremely super massive black hole in its core. Researches using the Very Large Telescope (VLT) and the Chandra X-ray Observatory have indicated the mass of the central black hole to be approximately two billion solar masses.
There is speculation is that NGC 3115, in its youth, was a quasar. The vast majority of its component stars are very old; however, spectrographic studies have indicated the central core is bluer than the surrounding galaxy indicating a merger with a companion galaxy (KK084). This merger is thought to have infused additional gas and led to new star formation in the core region of NGC 3115.
The faint background galaxy located to the left of NGC 3115 is designated PGC 29299. To my eye, it is probably a distant elliptical galaxy. I have not been able to locate any additional information for it.
NGC 3115 lies at a distance of approximately 32 million light years in the direction of the constellation Sextans.