NGC 3423
Face-on unbarred spiral galaxy with six spiral arms.
NGC 3423 is a spiral galaxy in the constellation Sextans, located about 45 million light years from Earth. It is notable as an unbarred galaxy seen nearly face-on, with a low-surface-brightness disk and multiple spiral arms.
Quick Facts
- Epoch
- J2000
- Ra
- 10 · 51 · 14.2926
- Dec
- +05 · 50 · 24.190
- Dist Ly
- 42 ± 7.9 Mly (12.9 ± 2.4 Mpc)
- Z
- 0.003349 ± 0.000007
- H Radial V
- 1,004 ± 2 km/s
- Appmag V
- 10.9
- Constellation Name
- Sextans
Facts from the source article.
Lore & Background
NGC 3423 was discovered by William Herschel on February 23, 1784. It is an unbarred spiral galaxy seen nearly face-on, featuring a low-surface-brightness disk. The galaxy has multiple spiral arms—at least six—with numerous HII regions scattered across the disk, the largest of which are about 2 arcseconds across. H-alpha emission is stronger in the inner part of the disk, and the star formation rate is estimated at 0.7 solar masses per year.
The galaxy is the foremost member of the NGC 3423 Group, which also includes MRK 1271. Nearby galaxies include NGC 3365, NGC 3495, and NGC 3521. During the March 2026 lunar eclipse, a total lunar eclipse, NGC 3423 was occulted by the Moon over North America.
One supernova and one luminous blue variable have been observed in NGC 3423. SN 2009ls was discovered on 23 November 2009 by Koichi Nishiyama and Fujio Kabashima at an apparent magnitude of 15.3; its spectrum revealed it was a young Type II supernova. AT 2019ahd was discovered by ATLAS on 29 January 2019 and identified as a luminous blue variable in outburst.
Reader's Guide
NGC 3423 holds significance as a nearby, face-on spiral galaxy that offers a clear view of its multiple spiral arms and HII regions, making it a useful target for studying star formation processes in a low-surface-brightness disk. Its star formation rate of 0.7 solar masses per year provides a benchmark for similar galaxies. The galaxy's role as the foremost member of the NGC 3423 Group places it in a local galactic context, with nearby companions such as NGC 3365, NGC 3495, and NGC 3521. The observation of a Type II supernova (SN 2009ls) and a luminous blue variable in outburst (AT 2019ahd) within NGC 3423 adds to its legacy as a site of transient stellar phenomena. The occultation of NGC 3423 by the Moon during the March 2026 total lunar eclipse over North America is a rare observational event that highlights the galaxy's position in the sky. These combined features make NGC 3423 a valuable object for both professional and amateur astronomers interested in galaxy structure, star formation, and transient events.
Did You Know?
- NGC 3423 has at least six spiral arms.
- SN 2009ls, a young Type II supernova, was discovered in NGC 3423 on 23 November 2009.
Frequently Asked Questions
What is NGC 3423?
NGC 3423 is an unbarred spiral galaxy sitting in the constellation Sextans, roughly 45 million light years from Earth. It stretches about 50,000 light years across and displays six spiral arms.
Who discovered NGC 3423 and when?
William Herschel first cataloged the galaxy on February 23, 1784, as part of his extensive surveys of deep-sky objects.
Why do astronomers find NGC 3423 visually interesting?
Its nearly face-on orientation lets observers see the full low-surface-brightness disk and all six spiral arms without the tilting distortion common in edge-on galaxies. The lack of a central bar also makes it a useful comparison point for studying how spiral structure forms.
How active is NGC 3423 in forming new stars?
The galaxy produces approximately 0.7 new stars each year, a modest but steady pace of stellar birth for a system its size.
Where in the sky can I find NGC 3423?
Search toward the faint constellation Sextans, nestled between Leo and Crater in the northern sky. At 45 million light years it is far beyond naked-eye reach, so a telescope is needed to make out its spiral features.
More in NGC Objects, Part 6 1-24
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