NGC 1325

Lore & Background

NGC 1325 is a barred spiral galaxy with a Hubble classification of SBbc, indicating moderately wound spiral arms. Its disk is inclined at an angle of 71° to the line of sight, with the major axis aligned along a position angle of 232°. The galaxy's rotation curve remains flat across much of its radius from the core, a characteristic common in spiral galaxies. It is receding from the Milky Way at a heliocentric radial velocity of 1,588 km/s.

Two supernovae have been observed in NGC 1325. SN 1975S was discovered by Justus Dunlap and Yvonne Dunlap at Corralitos Observatory on 30 December 1975, with a magnitude of 14.6. Its color and rapid lightcurve decline suggest it was a Type II supernova. SN 2021yja was discovered by ATLAS on September 8, 2021, with a magnitude of 15.334. Initially categorized as a Type II core-collapse supernova, it may instead be a Type Ic.

The galaxy is a member of the Eridanus Cluster, a large group of about 200 galaxies. Its flocculent structure and the presence of two supernovae make it an object of interest for studies of stellar evolution and galactic dynamics.

Reader's Guide

NGC 1325 holds significance as a member of the Eridanus Cluster, one of the nearer galaxy clusters, providing a laboratory for understanding galaxy interactions and evolution within a group environment. Its flocculent spiral structure, combined with a flat rotation curve, offers insights into dark matter distribution in barred spirals. The two supernovae recorded in this galaxy—SN 1975S, a Type II event with a rapid decline, and SN 2021yja, a core-collapse supernova whose classification remains uncertain between Type II-P and Type Ic—contribute to the study of massive star deaths and progenitor systems. The discovery of SN 1975S by the Dunlaps at Corralitos Observatory and SN 2021yja by the ATLAS survey highlights the ongoing monitoring of this galaxy for transient events. NGC 1325's well-measured radial velocity and inclination aid in kinematic modeling, while its angular size and position angle provide a clear view of its orientation. As part of the Eridanus Cluster, it helps astronomers map the large-scale structure of the local universe, and its historical discovery by William Herschel in 1799 places it among the earliest cataloged galaxies in this region.

Did You Know?

• It is a flocculent spiral galaxy with a Hubble classification of SBbc.
• Two supernovae have been observed: SN 1975S (Type II) and SN 2021yja (Type II-P or Type Ic).
• The galaxy is moving away from the Milky Way at 1,588 km/s.