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NGC 4565, often referred to as the Needle Galaxy, is a striking edge-on spiral galaxy located in the constellation Coma Berenices, 42 million light-years away. It is one of the most prominent examples of an edge-on galaxy and provides astronomers with an insight into the structure and composition of spiral galaxies seen from the side. With an apparent magnitude of around 10.4, it is observable through medium-sized amateur telescopes, where its elongated profile and central bulge are especially impressive. This galaxy was missed by Messier and was discovered by Herschel. It is quite bright and large and a conspicuous dust lane crosses across the nucleus of the galaxy.
From an astrophysical perspective, NGC 4565 is classified as an Sb-type spiral galaxy. Its nearly edge-on orientation allows us to study the thin disk, dust lanes, and bulge without the projection effects present in face-on systems. The prominent dust lane bisecting its luminous disk is a key feature, revealing regions of dense interstellar medium where star formation occurs. The stellar bulge, slightly elongated, hints at the presence of a central bar structure, a common feature in spiral galaxies that influences the flow of gas toward the core.
Studies with infrared and radio observations have shown that NGC 4565 contains a rich population of older stars in its bulge and a more active disk with molecular gas. Its rotation curve suggests the presence of a significant dark matter halo, as with most large spiral galaxies. The nucleus likely hosts a supermassive black hole, though it appears relatively quiescent compared to active galactic nuclei. Amazingly enough, there are, in the literature, no estimations of the mass of any supermassive black hole (SMBH) in its center, probably due to its low activity level. The only reference giving some hints about its mass, uses the den Brok (2015) formula based on molecular hydrogen kinematics. This estimation (that can be off by a wide margin) gives a possible mass for the SMBH between 105 and 106 solar masses.
Additional Information
Object
Name(s): NGC 4565. Caldwell 38. Needle Galaxy
Type: Sb-type spiral galaxy
RA: 12h 36m 20s
Dec: +25º 59’ 22”
Constellation: Coma Berenices
Size (arcmin): 16×2 arcmin
Magnitude: +9.6
Distance: 42 Ly
Image
Date: 2024-06-05 to 2024-06-29
Location: Curiosity3 Observatory, Utah Desert Remote Observatories, UT, USA
Size (arcmin): 30×30 arcmin
Telescope: 24” (61 cm) f/6.5 Reflector
Camera: FLI PL16803 (4096x4096pix)
Guiding: Astrodon MonsterMOAG off-axis guider
Total exposure: 13 hours (L: 5h; R: 2h 30m; G: 1h 45m; B: 1h 45m)
Processing: CCDStack, PixInsight (one step) and Photoshop CC 2024