NGC 3504
Barred starburst galaxy with a star-forming nuclear disk.
NGC 3504 is a barred spiral galaxy found in the constellation Leo Minor. It lies at a Hubble distance of about 88 million light-years and was first spotted by William Herschel on 11 April 1785. The galaxy has a luminosity class of I–II and a broad HI line, with regions of ionized hydrogen. It is also classified as a starburst galaxy.
A large amount of molecular gas is concentrated at the galactic nucleus. Compared to other barred spirals, NGC 3504 is considered to be in an early evolutionary stage. Its morphology is type (R1')SAB(rs)ab. The galaxy features a bright, point-like nucleus embedded in its bulge, crossed by a thin bar. Spiral arms wrap around an inner ring and then peel away to form an outer, broken pseudo-ring. There is little evidence of star formation in the galaxy overall.
The Hubble Space Telescope has detected a star-forming disk around the nucleus, with an axis estimated at 200 parsecs (about 650 light-years). The galaxy’s mass is difficult to pin down but is thought to lie between 2.5 × 10⁹ and 9 × 10⁹ solar masses. Its supermassive black hole, based on near-infrared K-band brightness measurements of the bulge, is estimated at 10⁷·⁸ solar masses, or about 63 million solar masses.
Two supernovae have been observed in NGC 3504. SN 1998cf (magnitude 15, type unknown) was discovered in March 1998 by Eric Emsellem using CCD images from the Canada-France-Hawaii Observatory, and also by Karl Gordon and Geoffrey Clayton of Louisiana State University. SN 2001ac (magnitude 18.2) was found by LOTOSS on 12 March 2001. Initially thought to be a Type IIn or a luminous blue variable, later analysis identified it as a calcium-rich supernova, sometimes called a "gap" transient.
NGC 3504 is the brightest member of the NGC 3504 Group (also known as LGG 227), which belongs to the Leo II Groups—a chain of galaxies and clusters stretching from the right edge of the Virgo Supercluster. The group includes eight other galaxies: NGC 3414, NGC 3512, UGC 5958, and others. This group was also referenced by Abraham Mahtessian in a 1998 research paper.
Quick Facts
- Epoch
- J2000
- Ra
- 11 · 03 · 11.2388
- Dec
- +27 · 58 · 21.344
- Z
- 0.005074 · 0.00000334ned
- Constellation Name
- Leo Minor
- Appmag V
- 11.67
Facts from the source article.
Lore & Background
NGC 3504 was discovered by German-British astronomer William Herschel on 11 April 1785. It is classified as a type (R1')SAB(rs)ab galaxy, featuring a bright point-like nucleus embedded in its bulge and crossed by a thin bar. Its spiral arms wrap around an inner ring and then peel off to form an outer, broken pseudo-ring. The galaxy shows little evidence of star formation overall, yet a star-forming disk around the nucleus has been identified by the Hubble Space Telescope, with an axis size estimated at 200 parsecs (about 650 light-years).
The galaxy contains a large amount of molecular gas centered on its nucleus. Compared with other barred spiral galaxies, NGC 3504 is considered to be in an early phase of its evolution. Its mass is difficult to narrow down but is believed to lie between 2.5×10⁹ and 9×10⁹ solar masses. The supermassive black hole at its center is estimated at 10^7.8 solar masses (63 million solar masses) based on near-infrared K-band brightness measurements of the galaxy's bulge.
Two supernovae have been observed in NGC 3504: SN 1998cf (type unknown, magnitude 15) discovered in March 1998 by Eric Emsellem via CCD images at the Canada-France-Hawaii Observatory and also by Karl Gordon and Geoffrey Clayton from Louisiana State University; and SN 2001ac (type gap, magnitude 18.2) discovered by LOTOSS on 12 March 2001, initially thought to be Type IIn or a luminous blue variable but later concluded to be a calcium-rich supernova. NGC 3504 is the brightest member of the NGC 3504 Group (LGG 227), part of the Leo II Groups, which are strung out from the right edge of the Virgo Supercluster.
Reader's Guide
NGC 3504 holds significance as a starburst galaxy with a well-studied nuclear star-forming disk, providing insight into the early evolutionary phase of barred spiral galaxies. Its large reservoir of molecular gas concentrated at the nucleus makes it a valuable target for understanding the processes that trigger intense star formation in galactic centers. The galaxy's supermassive black hole mass, derived from near-infrared measurements, contributes to the calibration of black hole scaling relations. The two supernovae observed within it—SN 1998cf and the unusual calcium-rich SN 2001ac—add to its legacy as a site of transient astrophysical phenomena. As the brightest member of the NGC 3504 Group, it serves as a reference point for studying galaxy interactions and group dynamics within the Leo II Groups, which are part of the larger Virgo Supercluster. The group itself was cataloged by Abraham Mahtessian in a 1998 research paper. NGC 3504's combination of a bright nucleus, thin bar, inner ring, and broken outer pseudo-ring offers a clear example of complex barred spiral morphology in an early stage of evolution.
Did You Know?
- NGC 3504 is a starburst galaxy with a star-forming disk around its nucleus measuring about 200 parsecs (650 light-years) across.
- Two supernovae have been observed in NGC 3504: SN 1998cf (mag. 15) and SN 2001ac (mag. 18.2), the latter being a calcium-rich 'gap' transient.
Frequently Asked Questions
What is NGC 3504?
NGC 3504 is a barred spiral galaxy with a star-forming nuclear disk, classified under the morphological type (R1')SAB(rs)ab. It sits roughly 88 million light-years away in the constellation Leo Minor and is recognized as a starburst galaxy due to its active regions of ionized hydrogen.
Who first observed NGC 3504 and when?
The British astronomer William Herschel was the first to record the galaxy on 11 April 1785. His discovery added it to the New General Catalogue, where it has carried the designation NGC 3504 ever since.
How massive is NGC 3504, and what does it contain at its center?
The galaxy's total stellar mass falls somewhere between 2.5 and 9 billion solar masses, placing it in the luminosity class I–II range. At its core sits a supermassive black hole estimated at about 63 million solar masses, surrounded by a bright, point-like nucleus and a dense reservoir of molecular gas.
Why do astronomers consider NGC 3504 to be in an early evolutionary stage?
Compared with other barred spirals, NGC 3504 still exhibits a broad HI line and active star-forming regions rather than the more quiescent profiles seen in older systems. This suggests its bar structure and nuclear disk are still dynamically evolving, making it a useful benchmark for studying how barred galaxies mature.
What makes NGC 3504 interesting for observers and researchers?
Its combination of a prominent bar, a starburst-driven nuclear disk, and a well-characterized central black hole gives it a rich set of physical processes to study. For visual observers, the galaxy's luminosity class I–II means it can appear as a distinct, elongated smudge in large-aperture telescopes under dark skies in Leo Minor.
More in NGC Objects, Part 6 1-24
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