NGC 3124
A face-on barred spiral with a counter-rotating inner pattern.
NGC 3124 is a barred spiral galaxy in the constellation Hydra. It is seen almost face-on from Earth. Based on methods that do not rely on redshift, the galaxy lies roughly 110 million light-years away, which, given its apparent size, means it spans about 120,000 light-years across. Redshift measurements, however, place it at about 170 million light-years. John Herschel discovered it on March 23, 1835.
The galaxy’s bar, when observed in red light, looks more like two very open spiral arms that rotate in the opposite direction to the outer spiral arms. The dust within the bar, however, curves in the same direction as the outer spirals. Gas motion across the galaxy is consistent. According to Treuthardt and colleagues, this counter-rotation is likely a temporary feature rather than the result of a merger.
A ring sits between the bar and the outer spiral arms. Two tightly wound spiral arms emerge from the ends of the bar, nearly overlapping after half a revolution. Beyond that, they break into multiple fragments that can be traced for roughly another half revolution. These arms contain HII regions. At the galaxy’s center lies a supermassive black hole, though its mass is not specified.
NGC 3124 forms a pair with the galaxy 2MASX J10071106-1904039. It belongs to the NGC 3091 Group (also cataloged as LGG 186), which includes NGC 3052, NGC 3091, UGCA 185, and MCG -03-26-006. Other nearby galaxies are NGC 2989, NGC 3028, NGC 3072, NGC 3076, NGC 3085, and NGC 3096.
Quick Facts
- Epoch
- J2000
- Ra
- 10 · 06 · 39.9044
- Dec
- -19 · 13 · 17.421
- Dist Ly
- 111 ± 29.5 Mly (34.2 ± 9.1 Mpc)
- Z
- 0.011882 ± 0.000013
- H Radial V
- 3,562 ± 4 km/s
- Appmag V
- 12.0
- Constellation Name
- Hydra
- Group Cluster
- NGC 3091 Group (LGG 186)
Facts from the source article.
Lore & Background
NGC 3124 was discovered by John Herschel on March 23, 1835. The galaxy is seen nearly face-on and is classified as barred, though in red light the bar resolves into two very open spiral arms that swirl in the opposite direction to the outer spiral arms. The dust within the bar, however, curves in the same direction as the outer spirals, and the gas kinematics remain consistent across the galaxy. Treuthardt et al suggest that this counter-rotation is transient and not the result of a merger.
A ring has formed between the bar and the outer spiral arms. Two tightly wound spiral arms emerge from the ends of the bar; after half a revolution they nearly overlap, then branch into multiple fragments that can be traced for about another half revolution. The arms contain HII regions. At the galaxy's center lies a supermassive black hole, though its mass is not specified.
NGC 3124 forms a pair with 2MASX J10071106-1904039 and is a member of the NGC 3091 Group (LGG 186), which also includes NGC 3052, NGC 3091, UGCA 185, and MCG -03-26-006. Other nearby galaxies include NGC 2989, NGC 3028, NGC 3072, NGC 3076, NGC 3085, and NGC 3096.
Reader's Guide
NGC 3124 is significant as an example of a barred spiral galaxy exhibiting a counter-rotating inner spiral pattern, a phenomenon that challenges simple models of galactic evolution. The bar's appearance in red light as two open arms swirling opposite to the outer arms, combined with dust that curves in the same direction as the outer spirals, indicates complex internal dynamics. The suggestion that this counter-rotation is transient—rather than the result of a merger—offers insight into the temporary structural changes that can occur in disk galaxies. The galaxy's membership in the NGC 3091 Group places it within a larger cosmic neighborhood, and its pairing with 2MASX J10071106-1904039 suggests possible gravitational interactions. The presence of HII regions in its spiral arms indicates ongoing star formation. NGC 3124 is often compared to NGC 4622, another galaxy with a counter-rotating inner spiral pattern, making it a useful object for studying the mechanisms behind such unusual kinematics.
Did You Know?
- NGC 3124 is a member of the NGC 3091 Group, also known as LGG 186.
- The galaxy's bar appears in red light as two very open spiral arms swirling opposite to the outer arms.
- The dust in the bar curves in the same direction as the outer spiral arms.
More in NGC Objects, Part 5 1-24
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