NGC 4725
A disturbed double-barred spiral with a star-forming ring.
NGC 4725 is an intermediate barred spiral galaxy in the northern constellation Coma Berenices, close to the north galactic pole. It was discovered by the German-born British astronomer William Herschel on April 6, 1785. The galaxy sits about 12.3 megaparsecs from the Milky Way and is the brightest member of the Coma I Group, part of the larger Coma-Sculptor Cloud, though it is fairly isolated from the group’s other galaxies. NGC 4725 is strongly disturbed and interacts with its neighbor, the spiral galaxy NGC 4747; its spiral arms show signs of warping. The two galaxies are separated by an angular distance that corresponds to a projected linear separation of 112 kiloparsecs, and a tidal plume extends from NGC 4747 toward NGC 4725.
This galaxy is a suspected type 2 Seyfert galaxy, hosting a supermassive black hole at its core. Its morphological classification is SAB(r)ab pec, meaning it is a peculiar, weakly barred spiral with a complete ring around the bar and somewhat tightly wound arms. NGC 4725 is actually double-barred, a feature found in about a third of all barred spirals. The galactic plane is tilted about 46° relative to Earth’s line of sight.
The galaxy’s ring structure is a site of star formation, offset from the center and showing non-circular motion. A compact radio source lies about 1.9 kiloparsecs from the nucleus, with no optical counterpart, suggesting it may be a star-forming region heavily obscured by dust.
Several supernova candidates have been detected in NGC 4725. SN 1940B, a Type II supernova, was discovered by Josef J. Johnson on a photograph taken May 5, 1940, northeast of the galactic core. SN 1969H (Type I, magnitude 15) was found by Anthony Fairall on July 8, 1969 (many sources incorrectly list the date as June 17, 1969). Candidate SN 1987E, detected on April 24, 1987 at magnitude 15.65, was later found to be a high proper motion foreground star after follow-up studies failed to confirm it. SN 1999gs (type unknown, magnitude 19.3) was discovered by the Lick Observatory Supernova Search on December 28, 1999, positioned west and south of the nucleus. On July 5, 2016, a magnitude 17.0 transient source, designated ASASSN-16gu (AT 2016cyu), was spotted at an angular separation from the nucleus. Initially thought to be a supernova, it was later identified as the Kuiper belt object Makemake, a dwarf planet.
Quick Facts
- Constellation Name
- Coma Berenices
- Epoch
- J2000
- Ra
- 12 · 50 · 26.56929
- Dec
- +25 · 30 · 02.7376
- Dist Ly
- 12.3 ±
- Appmag V
- 10.1
Facts from the source article.
Lore & Background
NGC 4725 was discovered by German-born British astronomer William Herschel on April 6, 1785. It lies at a distance of approximately 12.3 Mpc from the Milky Way. The galaxy is strongly disturbed and interacting with NGC 4747; its spiral arms show indications of warping, and a tidal plume extends from NGC 4747 toward NGC 4725. The pair have an angular separation corresponding to a projected linear separation of 112 kpc.
The galaxy's morphological classification is SAB(r)ab pec, indicating a peculiar, weakly-barred spiral with a complete ring surrounding the bar and somewhat tightly-wound spiral arms. It is actually double-barred, a feature found among about a third of all barred spirals. The galactic plane is inclined by approximately 46° to the line of sight. The ring structure is a region of star formation, offset from the galactic center and displaying non-circular motion. A compact radio source is positioned approximately 1.9 kpc from the nucleus, with no optical counterpart, possibly a heavily obscured star-forming region.
NGC 4725 is a suspected type 2 Seyfert galaxy with a supermassive black hole at its core. Multiple supernova candidate events have been detected, including SN 1940B (Type II), SN 1969H (Type I), and SN 1999gs. Candidate SN 1987E was later determined to be a high proper motion foreground star. A transient source in 2016, initially thought to be a supernova, was identified as the Kuiper belt object Makemake.
Reader's Guide
NGC 4725 holds significance as the brightest member of the Coma I Group, despite its relative isolation from other members. Its disturbed morphology and interaction with NGC 4747 provide a natural laboratory for studying galaxy interactions and tidal effects. The double-barred structure, present in only about a third of barred spirals, offers insight into the dynamics of galactic bars and their evolution. The star-forming ring, offset from the center and exhibiting non-circular motion, is a key feature for understanding star formation processes in ring galaxies. The suspected type 2 Seyfert nucleus with a supermassive black hole adds to its importance for active galactic nucleus studies. The galaxy's history of supernova detections, including the misidentification of Makemake as a supernova in 2016, highlights the challenges of transient astronomy. The compact radio source without an optical counterpart suggests heavily obscured star formation, contributing to knowledge of dust-enshrouded regions in galaxies. Overall, NGC 4725 serves as a valuable object for multiple astrophysical investigations, from galaxy dynamics to supernova physics.
Did You Know?
- The galaxy's ring structure is offset from the center and shows non-circular motion.
- SN 1969H was discovered by Anthony Fairall on 8 July 1969, though many sources incorrectly report the date as 17 June 1969.
More in Galaxy Clusters and Groups, Part 4 1-24
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