NGC 1309

Lore & Background

NGC 1309 was discovered by German-British astronomer William Herschel on 3 October 1785. Its spiral arms display bright blue areas of star formation, while the yellowish central nucleus contains older-population stars. The galaxy is the brightest member of a trio that also includes MCG-03-09-027 and UGCA71, collectively known as the NGC 1309 group or LGG 92. It is one of over 200 galaxies belonging to the larger Eridanus Group.

Two supernovae have been observed in NGC 1309. SN 2002fk, a Type Ia supernova of magnitude 15, was discovered jointly by Reiki Kushida of the Yatsugatake South Base Observatory, Japan, and Jun-jie Wang and Yu-Lei Qiu of the Beijing Astronomical Observatory on 17 September 2002. It reached an estimated maximum magnitude of about 13.0. Its spectra showed no hydrogen, helium, or carbon, but revealed ionized calcium, silicon, iron, and nickel.

SN 2012Z, a Type Iax supernova of magnitude 17.6, was discovered jointly by Brad Cenko, Weidong Li, and Alex Filippenko using the Katzman Automatic Imaging Telescope on 29 January 2012 as part of the Lick Observatory Supernova Search. Scientists hypothesized that this supernova may have left behind a remnant zombie star. In February 2022, new observations confirmed that the star survived the explosion and is even brighter than before.

Reader's Guide

NGC 1309 holds significance as a well-studied spiral galaxy within the Eridanus Group, offering insights into star formation and stellar populations. Its bright blue star-forming regions and older yellow nucleus illustrate the typical structure of an SA(s)bc galaxy. The galaxy's role as the brightest member of its own small group (LGG 92) highlights its gravitational dominance among its companions.

The two supernovae observed in NGC 1309 have contributed to supernova science. SN 2002fk, a Type Ia, provided spectra rich in intermediate-mass elements, aiding understanding of thermonuclear explosions. SN 2012Z is particularly notable as a Type Iax supernova where the progenitor star apparently survived the explosion and became brighter afterward, challenging conventional models of supernova outcomes. This surviving 'zombie star' has been confirmed by later observations, making NGC 1309 a key object for studying unusual supernova remnants. The galaxy's legacy lies in its dual role as a typical spiral and a host to exceptional stellar events.

Did You Know?

• NGC 1309 is about three-quarters the width of the Milky Way.
• It was discovered by William Herschel on 3 October 1785.
• SN 2012Z may have left behind a surviving zombie star that became brighter after the explosion.