NGC 3729

Lore & Background

NGC 3729 was discovered by William Herschel on April 12, 1789. It lies at a distance of roughly 65 million light years from Earth and spans about 60,000 light years across. The galaxy features a bright nucleus embedded in a bar measuring 0.5 by 0.1 arcminutes. At the end of the bar lies a ring with knots, and the outer part consists of an asymmetric faint nebulosity with condensations; one condensation may be a disturbed satellite galaxy. In its center, an intermediate-mass black hole is predicted, with a mass estimated between 4 and 400 thousand solar masses (104.6 ± 1.0) based on Ks-band bulge luminosity. The galaxy has an inner ring that emits in far ultraviolet and H-alpha, markers of recent star formation activity. NGC 3729 is a member of the M109 Group, part of the south Ursa Major groups within the Virgo Supercluster. It forms a pair with NGC 3718, located 11.5 arcminutes to the west, and the two may have interacted in the past. No supernovae have been observed in NGC 3729, but a luminous red nova, designated AT 2018hso, was discovered on October 31, 2018 (type LRN, magnitude 19.4).

Reader's Guide

NGC 3729 is significant as a barred spiral galaxy that exhibits structural features indicative of past or ongoing interactions, particularly its asymmetric outer nebulosity and possible satellite condensation. Its pairing with NGC 3718, only 11.5 arcminutes away, suggests a gravitational interaction that may have shaped both galaxies. The presence of an inner ring emitting in far ultraviolet and H-alpha points to recent star formation, while the predicted intermediate-mass black hole in its center adds to its astrophysical interest. The detection of a luminous red nova, AT 2018hso, in 2018 provides a rare transient event in an otherwise supernova-free galaxy, offering insight into stellar mergers or eruptions. As a member of the M109 Group and the Virgo Supercluster, NGC 3729 contributes to the understanding of galaxy group dynamics and large-scale structure. Its legacy lies in its combination of morphological peculiarities, black hole mass constraints, and transient phenomena, making it a subject for studies of galaxy evolution and interaction.

Did You Know?

• It is located about 65 million light years from Earth and is about 60,000 light years across.
• A luminous red nova, AT 2018hso, was discovered in NGC 3729 on October 31, 2018.
• The galaxy is predicted to host an intermediate-mass black hole with a mass between 4 and 400 thousand solar masses.