NGC 2336

Lore & Background

NGC 2336 is a barred spiral galaxy featuring a small optical bar. At least eight spiral arms, with numerous HII regions, emanate from a ring-like structure around the bar. This ring has a radius of approximately 34 arcseconds, corresponding to 5.3 kpc at the galaxy's distance. In the large arms, 28 HII regions have been observed that may host young massive star clusters; for two of them, nebular emission comprises most of the flux. Three of these HII areas have ages calculated to be 100 to 300 million years and sizes between 300 and 600 parsecs, and it is suggested they are star complexes that may coexist with younger ones. The most massive HII region, number 13, has a mass estimated to be and is 810 pc across. Observations in the ultraviolet showed 78 star-forming regions, with two between the spiral arms and six at the galaxy ring; their size is comparable to NGC 604, one of the largest nebulae in the Local Group. Star formation is more intense in the inner parts of the arms and at the ring.

Scattered dust lanes that do not fit into a spiral structure have been observed in the nuclear region. No emission has been detected in radiowaves, and HI and Hα imaging of the nucleus show no emission. The nucleus is small, with an apparent diameter of 5 arcseconds, while the bulge is large, with a radius of 17 arcseconds. At the center lies a supermassive black hole whose mass is estimated to be 30 million solar masses based on Ks bulge luminosity. NGC 2336 also hosts an active Type II Seyfert galactic nucleus, discovered by the Ultraviolet Imaging Telescope (UVIT).

One supernova has been observed in NGC 2336: SN1987L (Type Ia, magnitude 14.2), discovered by American amateur astronomer James Dana Patchick on 16 August 1987 using a home-built 17.5-inch Dobsonian reflecting telescope. The supernova was found as part of a team effort known as 'SUNSEARCH', started by Steve H. Lucas. Spectrography performed by the William Herschel Telescope on 20–21 October 1987 concluded it was a Type Ia supernova with its maximum approximately 100 days before. NGC 2336 is the foremost galaxy of a small group known as the NGC 2336 group and forms a non-interacting pair with IC 467, which lies 20 arcminutes away.

Reader's Guide

NGC 2336 stands out as a large barred spiral galaxy with a complex structure of at least eight spiral arms and a prominent ring around its bar. Its numerous HII regions, including 28 in the large arms and 78 star-forming regions detected in ultraviolet, indicate ongoing star formation, particularly intense in the inner arms and ring. The presence of a supermassive black hole of 30 million solar masses and an active Type II Seyfert nucleus highlights its energetic core. The galaxy's discovery by Wilhelm Tempel in 1876 and the visual discovery of supernova SN1987L by amateur astronomer James Dana Patchick underscore its place in both professional and amateur astronomy. As the leading member of the NGC 2336 group, it provides a context for studying galaxy interactions and star formation in a non-interacting pair with IC 467. The detailed observations of its HII regions, including ages and sizes, contribute to understanding star complex evolution. The lack of radio and HI/Hα emission from its nucleus, despite its active nucleus, presents an interesting contrast. Overall, NGC 2336 serves as a valuable object for studying barred spiral structure, star formation processes, and active galactic nuclei.

Did You Know?

• NGC 2336 spans about 200,000 light years across, roughly twice the diameter of the Milky Way.
• The galaxy has at least eight spiral arms emanating from a ring-like structure around its bar.
• The central supermassive black hole has an estimated mass of 30 million solar masses.