NGC 7479

Lore & Background

William Herschel discovered NGC 7479 in 1784. The galaxy is recognized as a Seyfert galaxy and a LINER, with starburst activity occurring not only in the nucleus and outer arms but also across the bar, where most stars formed in the last 100 million years. Polarization studies indicate that NGC 7479 recently underwent a minor merger, which is attributed to its asymmetrical arms, intense star formation, and a unique feature in the radio continuum: its radio arms open in a direction opposite to the optical arms. The galaxy is similar in both size and morphology to the barred spiral NGC 1300. Two supernovae have been observed: SN 1990U (Type Ic, mag. 16) discovered on 27 July 1990, and SN 2009jf (Type Ib, mag. 18) discovered on 27 September 2009.

Reader's Guide

NGC 7479's significance lies in its unusual radio continuum, where the radio arms open opposite to the optical arms—a feature attributed to a recent minor merger. This merger also explains the galaxy's asymmetrical arms and intense starburst activity across the bar, nucleus, and outer arms. As a Seyfert galaxy and LINER, it provides a laboratory for studying active galactic nuclei and star formation triggered by galactic interactions. Its similarity to NGC 1300 in size and morphology offers comparative insights into barred spiral evolution. The two recorded supernovae, SN 1990U and SN 2009jf, add to its observational history, though their specific contributions are not detailed beyond their types and magnitudes.

Did You Know?

• NGC 7479 is also called the Superman Galaxy.
• Its radio arms open in the opposite direction to its optical arms.
• Most stars in its bar formed within the last 100 million years.

Discovery & Identity

First recorded by the pioneering astronomer William Herschel in 1784, NGC 7479 has been a recognized deep-sky object for over two centuries. Situated roughly 105 million light-years from Earth, this barred spiral galaxy resides in the northern constellation Pegasus, where it is also catalogued under the designation Caldwell 44. Amongst amateur astronomers and enthusiasts, it has earned the colorful nickname the Superman Galaxy, a moniker that reflects its striking visual character. In terms of structural classification, NGC 7479 shares notable similarities with the well-known barred spiral NGC 1300, matching it in both overall size and morphological features. The galaxy's barred structure, a dense central bar of stars connecting the spiral arms, gives it a distinctive appearance that sets it apart from unbarred spirals. Its inclusion in both the New General Catalogue and the Caldwell catalogue underscores its significance as a deep-sky target for observers with modest telescopes, while its distance places it firmly in the realm of extragalactic astronomy rather than the Milky Way's own stellar population.

Starburst & Active Nucleus

NGC 7479 is classified as both a Seyfert galaxy and a LINER, designations that point to an active galactic nucleus powered by processes distinct from ordinary starlight. What makes this object particularly remarkable is the extraordinary breadth of its starburst activity. Rather than being confined to a single region, intense star formation is occurring simultaneously across the central nucleus, along the outer spiral arms, and throughout the bar of the galaxy. This widespread burst of stellar creation is not a slow, steady process; the overwhelming majority of the galaxy's stellar population was generated within the last 100 million years, a remarkably brief span in cosmic terms. The coexistence of a Seyfert-type active nucleus with such vigorous, galaxy-wide star formation suggests that NGC 7479 is in a dynamic transitional phase. The bar, which in many barred spirals serves primarily as a channel for gas inflow toward the center, here appears to be a site of its own intense stellar birth, adding another layer of complexity to the galaxy's energetic output and making it a compelling target for studying the interplay between nuclear activity and distributed star formation.

Merger Evidence & Radio Uniqueness

Polarization studies of NGC 7479 have revealed compelling evidence that the galaxy recently experienced a minor merger with a smaller companion. This gravitational encounter appears to be the driving force behind several distinctive features observed in the system. The spiral arms are notably asymmetrical, lacking the balanced, mirror-image structure seen in many undisturbed barred spirals. Perhaps most strikingly, the galaxy is unique in its radio continuum emission: the radio arms open in a direction opposite to that of the optical arms. This unusual misalignment between the radio and optical structures has no simple explanation in standard spiral galaxy models and is attributed directly to the disruptive effects of the merger. The collision with a smaller galaxy likely injected fresh gas into the system, triggering the widespread starburst activity observed across the nucleus, bar, and outer arms. Together, the asymmetrical morphology, the reversed radio arm orientation, and the intense star formation paint a coherent picture of a galaxy still recovering from a relatively recent gravitational encounter, making NGC 7479 a valuable natural laboratory for understanding how mergers reshape spiral structure.

Supernovae in NGC 7479

Throughout its modern observational history, NGC 7479 has been the site of two confirmed supernova events, each detected by dedicated automated survey programs. The first, designated SN 1990U, was identified on 27 July 1990 by the Berkeley Automated Supernova Search. Classified as a Type Ic supernova, it reached an apparent magnitude of 16, making it a challenging but detectable target for large-aperture instruments. Nearly two decades later, on 27 September 2009, the Lick Observatory Supernova Search recorded a second explosion in the galaxy, catalogued as SN 2009jf. This event was classified as a Type Ib supernova and peaked at a fainter apparent magnitude of 18. The occurrence of two core-collapse supernovae of different subtypes within a single galaxy over a span of less than twenty years is consistent with the intense, ongoing star formation that characterizes NGC 7479. Massive stars born in the recent starburst episodes have already reached the end of their short lives, exploding and enriching the surrounding interstellar medium with heavy elements. These events also provide astronomers with valuable data on the stellar populations and chemical evolution of a distant barred spiral in an active phase.