NGC 1042
A late-type spiral galaxy with an intermediate-mass black hole.
NGC 1042 is a spiral galaxy in the constellation Cetus, first spotted by American astronomer Lewis Swift on 10 November 1885. It shines with an apparent magnitude of 14.0. This galaxy is classified as a low-luminosity active galaxy, with a luminosity class of III–IV and a broad HI line. At its core lies an intermediate-mass black hole, and it also hosts an ultraluminous X-ray source known as NGC 1042 ULX1.
Morphologically, NGC 1042 is a late-type galaxy with a classification of SAB(rs)cd. It lacks a bulge and features spiral arms that include two symmetric inner arms and long, continuous outer arms, earning an Arm Class of 9. Its exact spiral type is debated: some astronomers, using ellipse fitting on B- and H-band images, classify it as a barred spiral, while others consider it unbarred. Further analysis suggests that the inner arms curve into a bar-like structure that may be mistaken for a true bar.
In the sky, NGC 1042 lies near the spiral galaxy NGC 1035, and both have similar redshifts, hinting at a physical association. NGC 1042 is also a member of the NGC 1052 group. It is the only galaxy in that group with a large gas reservoir, indicating that it lost gas during a past interaction with NGC 1052.
Quick Facts
- Epoch
- J2000
- Ra
- 02 · 40 · 24.0
- Dec
- -08 · 26 · 01
- Constellation Name
- Cetus
- Z
- 0.004573 ± 0.000007
- Dist Ly
- 55.5 Mly (17.02 Mpc)
- Group Cluster
- NGC 1052 group
- Appmag V
- 14.0
- H Radial V
- 1,371 ± 2 km/s
Facts from the source article.
Lore & Background
NGC 1042 was discovered on 10 November 1885 by American astronomer Lewis Swift. It is a late-type galaxy classified as type SAB(rs)cd, with a bulgeless structure and spiral arms consisting of two symmetric inner arms and ceaseless long outer arms, receiving an Arm Class 9 classification. The galaxy's spiral type is disputed: some astronomers classify it as a barred spiral galaxy based on ellipse fitting via B- and H-band images, while others classify it as an unbarred spiral galaxy. Further evidence suggests the inner arms are curved with a bar-like structure that is mistaken for a bar.
The galaxy has a broad HI line and a luminosity class of III–IV. It hosts an intermediate-mass black hole at its center and contains an ultraluminous X-ray source called NGC 1042 ULX1. NGC 1042 appears near the spiral galaxy NGC 1035 in the sky, with both having similar redshifts, and the two may be physically associated. It is also a member of the NGC 1052 group and is shown to be the only galaxy in the group with a large gas reservoir, indicating it was stripped of gas during a past interaction with NGC 1052.
Reader's Guide
NGC 1042 holds significance as a low-luminosity active galaxy that provides a laboratory for studying intermediate-mass black holes and ultraluminous X-ray sources. Its disputed classification—whether it is a barred or unbarred spiral—highlights the challenges in interpreting galactic morphology, particularly when bar-like structures may be artifacts of curved inner arms. The galaxy's membership in the NGC 1052 group and its proximity to NGC 1035, with matching redshifts, suggest a physical association and possible past interactions. Notably, NGC 1042 is the only galaxy in the NGC 1052 group retaining a large gas reservoir, implying that it was stripped of gas during an interaction with NGC 1052. This makes it a key object for understanding gas dynamics and galaxy evolution in group environments. The presence of an ultraluminous X-ray source adds to its astrophysical interest, as such sources are often linked to black hole accretion processes. Its legacy lies in contributing to debates on spiral structure classification and the role of interactions in shaping galaxy properties.
Did You Know?
- The galaxy is a member of the NGC 1052 group.
- Its spiral type is disputed: some classify it as barred, others as unbarred.
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