NGC 3166
NGC 3166 is a lenticular galaxy in the constellation Sextans. The galaxy lies about 65 million light years away from Earth, which means, given its apparent dimensions, that NGC 3166 is approximately 105,000 light years across. It was discovered by William Herschel on December 19, 1783.
Characteristics
NGC 3166 has a bright, elongated nucleus, surrounded by an elliptical bright bulge, elongated along a nearly east-west axis. In the central 6-7 arcseconds there is evidence of a circumnuclear star disk. The age of the stars in the nucleus is estimated to be no older than two billion years. A low-surface-brightness bar is visible lying nearly perpendicular to that. The fainter parts of the bulge are nearly circular, about one arcminute in diameter, and with spiral whorls. Beyond that lies a low-surface-brightness disk, without spiral arms or knots. Dust lanes are visible over the disk of the galaxy. The stars in the disk have sub-solar metallicity, indicating the stars are more than 8 billion years old there.In ultraviolet the galaxy is asymmetric, with stronger emission west of the nucleus. That region, at the western tidal arm, is the only in the galaxy that has a spectrum similar to an HII region and is indicative of the presence of young stars. There is hydrogen emission east of the nucleus. This asymmetry could be the result of recent gas accretion, and a complete star formation ring hasn't yet formed. The current star formation rate of the galaxy is estimated to be per year. An arm is visible in H-alpha 100 arcseconds west of the nucleus. The outer regions of the galaxy appear lopsided.