NGC 550

NGC 550 is a lenticular galaxy located approximately 135 million light-years away in the constellation Cetus. It was discovered on November 8, 1885, by Lewis Swift. Lenticular galaxies, designated S0, are intermediate between spiral and elliptical galaxies. They possess a central bulge like elliptical galaxies, but also have a disk surrounding it, although this disk lacks prominent spiral arms.

NGC 550 is classified as a LINER galaxy, which stands for Low-Ionization Nuclear Emission-line Region. LINER galaxies are characterized by spectral line emission from weakly ionized or neutral atoms. The source of ionization in LINERs is still debated, but possibilities include photoionization by a weak active galactic nucleus (AGN), shock heating, or photoionization by hot, massive stars.

The galaxy has an apparent magnitude of around 13.5, making it a relatively faint object requiring a moderately sized telescope to observe. It is part of a small group of galaxies.