NGC 3169
A peculiar spiral galaxy with an active nucleus and interacting companion.
NGC 3169, a spiral galaxy in Sextans, lies about 75 million light-years from Earth. Its classification—SA(s)a pec—marks it as a pure, unbarred spiral with tightly coiled arms and unusual features, including an asymmetrical arm and an extended halo. This galaxy belongs to the NGC 3166 Group, itself part of the Leo II Groups, a chain of galaxies and clusters stretching from the eastern edge of the Virgo Supercluster.
At its core, NGC 3169 is a LINER 2 galaxy, showing extended X-ray emission. A hard X-ray source at the center likely signals an active galactic nucleus. The nucleus and a ring at an angular radius of 6 arcseconds contain a stellar population only one billion years old—younger than the surrounding stars—suggesting a burst of star formation occurred there about a billion years ago.
NGC 3169 lies very close to NGC 3166, with an estimated separation of about 160,000 light-years (50 kiloparsecs). Their gravitational interaction has warped NGC 3166’s disk. Together with NGC 3156, these three galaxies form a small group inside the larger Leo I group, all embedded in an extended ring of neutral hydrogen centered on NGC 3169.
Two supernovae have been observed in NGC 3169. SN 1984E (Type II-L, magnitude 14.5) was co-discovered by Nataliya Metlova on 26 March 1984 and by Robert Evans on 29 March 1984. Its spectrum at maximum light showed prominent Balmer lines, indicating the explosion occurred within a dense hydrogen shell around the star, likely produced by a strong stellar wind from the progenitor. SN 2003cg (Type Ia, magnitude 14.4) was co-discovered by Kōichi Itagaki and Ron Arbour on 21 March 2003.
Quick Facts
- Epoch
- J2000
- Ra
- 10 · 14 · 15.099
- Dec
- +03 · 27 · 58.03
- Dist Ly
- 57 Mly
- Z
- +0.0041130.000017
- Appmag V
- 10.3
- Constellation Name
- Sextans
Facts from the source article.
Lore & Background
NGC 3169 is classified as SA(s)a pec, indicating a pure, unbarred spiral galaxy with tightly-wound arms and peculiar features. It displays an asymmetrical spiral arm and an extended halo. The galaxy is a member of the NGC 3166 Group, which itself belongs to the Leo II Groups, a series of galaxies and galaxy clusters strung out from the right edge of the Virgo Supercluster.
The galaxy is a LINER 2 galaxy with an extended emission of X-rays in the nuclear region. A hard X-ray source at the center most likely indicates an active galactic nucleus. The stellar population in the nucleus and a ring at an angular radius of 6″ shows an age of only one billion years, generally younger than the surrounding stellar population, suggesting a burst of star formation took place in the nucleus roughly one billion years ago.
NGC 3169 is located in close physical proximity to NGC 3166, with an estimated separation of around 160 kly (50 kpc). Their interaction is creating a gravitational distortion that has left the disk of NGC 3166 warped. Combined with NGC 3156, the three galaxies form a small group within the larger Leo 1 group. The three are embedded within an extended ring of neutral hydrogen centered on NGC 3169.
Reader's Guide
NGC 3169 is significant as a nearby example of a peculiar spiral galaxy with an active galactic nucleus, providing insight into the processes of nuclear activity and star formation bursts. The detection of a hard X-ray source at its center most likely indicates an active galactic nucleus, while the young stellar population in the nucleus and a surrounding ring suggests a burst of star formation occurred roughly one billion years ago. Its physical interaction with NGC 3166, which has warped the disk of the latter, offers a case study in gravitational distortion between galaxies. The two supernovae observed in NGC 3169—SN 1984E, a Type II-L event that exploded inside a dense hydrogen shell, and SN 2003cg, a Type Ia—contribute to the understanding of supernova progenitors and their environments. The galaxy's membership in the NGC 3166 Group and the larger Leo II Groups places it within the broader structure of the Virgo Supercluster, and the extended ring of neutral hydrogen encompassing NGC 3169, NGC 3166, and NGC 3156 highlights the complex gas dynamics in this interacting system.
Did You Know?
- NGC 3169 is a LINER 2 galaxy with an extended X-ray emission in its nucleus.
- A burst of star formation occurred in the nucleus roughly one billion years ago.
- It is interacting with NGC 3166, warping that galaxy's disk.
- Two supernovae have been observed: SN 1984E (Type II-L) and SN 2003cg (Type Ia).
More in NGC Objects, Part 5 1-24
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