NGC 4666

NGC 4666 is a spiral galaxy in the equatorial constellation of Virgo, located at a distance of approximately 16.83 Mpc from the Milky Way. It was discovered by the German-born astronomer William Herschel on February 22, 1784. It is a member of the Virgo II Groups, a series of galaxies and galaxy clusters strung out from the southern edge of the Virgo Supercluster. John L. E. Dreyer described it as "bright, very large, much extended 45°±, pretty suddenly brighter middle". It is a member of an interacting system with NGC 4668 and a dwarf galaxy, and belongs to a small group that also includes NGC 4632.

The morphological classification of this galaxy is SABc, which indicates a weak bar around the nucleus with moderately wound spiral arms. Viewed nearly edge-on, its galactic plane is inclined at an angle of $1,517 km/s$ to the line of sight from the Earth, with the major axis aligned along a position angle of 40°. There is an active galactic nucleus that shows a modest level of activity and is most likely heavily obscured by gas and dust. The central point source has been detected in the radio and X-ray bands.

This is a starburst galaxy that is noteworthy for its vigorous star formation, which creates an unusual superwind of out-flowing gas. This wind is not visible at optical wavelengths, but is prominent in X-rays, and has been observed by the ESA XMM-Newton space telescope. The estimated star formation rate is $85 °$ yr–1, with a density of $7.3 solar mass$ yr−1 kpc−2. Unlike in many other starburst galaxies, the star formation is spread across the disk rather than being more concentrated.

Three supernovae have been observed in NGC 4666. On 23 May 1965, Enrique Chavira discovered SN 1965H (type IIP, mag. 14). A type Ia supernova was detected in NGC 4666 on 9 December 2014; ASASSN-14lp is located $8.9 solar mass$ from the center of NGC 4666. A type Ib supernova, SN 2019yvr, was detected on 27 December 2019. It has a 0.005 redshift. Images of the location of the supernova before the explosion showed the progenitor star was ~19.