NGC 877

Lore & Background

NGC 877 was discovered by William Herschel on October 14, 1784. It features two spiral arms in a grand design pattern with a slightly disturbed morphology. In H-alpha imagery, the arms display numerous knots and appear brighter than the nucleus, while the northwest part of the galaxy shows higher polarized emission than the rest. A bar is detected in radio waves. The nucleus exhibits activity resembling that of an HII region, and the galaxy is categorized as a luminous infrared galaxy, with total infrared luminosity near the threshold for that classification. Its total star formation rate is estimated between 20 and 53 solar masses per year.

The galaxy forms a pair with the edge-on spiral NGC 876, located 2.1 arcminutes to the southwest, corresponding to a projected separation of 30 kpc. A low surface brightness bridge connects the two galaxies. NGC 877 is the brightest and most massive member of the NGC 877 group (LGG 53), which also includes NGC 876, NGC 871, UGC 1693, IC 1791, UGC 1773, and UGC 1817. The group contains large amounts of HI gas. Nearby galaxies NGC 870 and NGC 871 are also in the vicinity.

One supernova has been observed in NGC 877: SN 2019rn, a Type IIb supernova discovered by the ATLAS survey on January 12.30, 2019, with an apparent magnitude of 18.86. It was initially classified as Type II but later reclassified as Type IIb based on further spectroscopic observations.

Reader's Guide

NGC 877 holds significance as a luminous infrared galaxy, a class associated with high star formation rates, and its total infrared luminosity lies near the threshold for that classification. Its interaction with NGC 876, evidenced by a low surface brightness bridge, provides a natural laboratory for studying galaxy interactions and their effects on star formation and morphology. The galaxy's grand design spiral arms, bright in H-alpha with numerous knots, indicate vigorous star-forming regions, while the polarized emission in the northwest suggests organized magnetic fields or dust structures. As the brightest and most massive member of the NGC 877 group, it anchors a system rich in HI gas, offering insights into group dynamics and gas content. The detection of a bar in radio waves adds to understanding of its internal structure. The occurrence of SN 2019rn, a Type IIb supernova, contributes to the record of stellar explosions in interacting systems. Additionally, NGC 877 will be occulted by the Moon during total lunar eclipses in October 2050 and October 2069, providing rare observational opportunities.

Did You Know?

• It interacts with the edge-on spiral galaxy NGC 876 via a low surface brightness bridge.
• SN 2019rn, a Type IIb supernova, was discovered in NGC 877 on January 12.30, 2019.