NGC 3621

NGC 3621 is a field spiral galaxy about 22 Mly away in the equatorial constellation of Hydra. It is comparatively bright and can be well seen in moderate-sized telescopes. The galaxy is around 93000 ly across and is inclined at an angle of 66° from being viewed face on. It shines with a luminosity equal to 13 billion times that of the Sun. The morphological classification is SA(s)d, which indicates this is an ordinary spiral with loosely wound arms. There is no evidence for a bulge. Although it appears to be isolated, NGC 3621 belongs to the Leo spur.

This galaxy has an active nucleus that matches a Seyfert 2 optical spectrum, suggesting that a low mass supermassive black hole is present at the core. Based upon the motion of stars in the nucleus, this object may have a mass of up to three million times the mass of the Sun.

One supernova has been observed in NGC 3621: SN 2024ggi (type II, mag. 18.9). It was discovered on 11 April 2024, and by 16 April it had brightened to magnitude 12. It is the closest supernova to Earth since SN 2023ixf, which was discovered on 19 May 2023.