NGC 3660
A barred spiral Seyfert galaxy with three observed supernovae.
NGC 3660 is a barred spiral galaxy located in the constellation Crater, approximately 200 million light-years away. It is notable as a Type 2 Seyfert galaxy with an active nucleus, discovered in February 1787 by William Herschel, who described it as a large faint object with an irregular appearance and a bright center.
Quick Facts
- Epoch
- J2000
- Constellation Name
- Crater
- Ra
- 11 · 23 · 32.27
- Dec
- -08 · 39 · 30.62
- Z
- 0.012285
- H Radial V
- 3,683 km/s ± 2
- Dist Ly
- 206 Mly (63.27 Mpc)
- Appmag V
- 12.2
- Names
- 2MASX J11233229-0839308, 6dF J1123322-083931, CGS 367, PGC 34980, IRAS 11210-0823, MCG -01-29-016, MRK 1291, NSA 139324
Facts from the source article.
Lore & Background
NGC 3660 is a barred spiral galaxy of type SBbc with an optical magnitude of 11.9. It is depicted as isolated, with a strong bar feature extending to about 16 arcseconds at a position angle of 116°, and a barely resolved ring based on K-band imaging. The bar region appears redder, and color mapping suggests a possible small circumnuclear region. The galaxy's active nucleus has a compact appearance. About 59 H II regions are distributed around the ring and along the spiral arms; those on the outskirts are more highly excited than those in the ring, particularly two regions northeast at 40 and 50 arcseconds from the nucleus. Faint regions to the southeast form a shell feature. A weak hydrogen alpha component has been detected with a full width at half maximum of 1,950 km/s. The galaxy is variable in both soft and hard X-rays. Molecular gas detections give a total mass of 0.80 × 10⁹ M☉ based on CO 1-0 observations.
Reader's Guide
NGC 3660 holds significance as an active Seyfert galaxy of Type 2, providing a nearby laboratory for studying nuclear activity and star formation in a barred spiral. Its strong bar and ring structure, along with the distribution of 59 H II regions, offer insights into how bars channel gas and trigger star formation. The detection of molecular gas and X-ray variability further characterize its active nucleus and interstellar medium. The galaxy has hosted three supernovae—SN 2017byz, SN 2018jlp, and SN 2026cff—all of Type II, with the most recent discovered in 2026 as part of the Unistellar 'cosmic cataclysms' smart telescope tracking project. These events contribute to the study of core-collapse supernovae in barred environments. The shell feature to the southeast and the redder bar region hint at past interactions or internal dynamics. Overall, NGC 3660 serves as a valuable object for understanding the interplay between bars, rings, nuclear activity, and stellar explosions in an isolated galaxy.
Did You Know?
- NGC 3660 was discovered in February 1787 by William Herschel.
- Three Type II supernovae have been observed in NGC 3660: SN 2017byz, SN 2018jlp, and SN 2026cff.
More in NGC Objects, Part 6 1-24
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