Barred spiral galaxy
Fornax
RA: 03 33 36
Dec: -36 08 25
Magnitude 10.3
Size: 11.2’ x 6.2’
Portrait_of_the_Great_Barred_Spiral.jpg
(By Dark Energy Survey/DOE/FNAL/DECam/CTIO/NOIRLab/NSF/AURA Image processing: Travis Rector (University of Alaska Anchorage/NSF’s NOIRLab), Jen Miller (Gemini Observatory/NSF’s NOIRLab), Mahdi Zamani & Davide de Martin (NSF’s NOIRLab) - https://noirlab.edu/public/images/iotw2127a/, CC BY 4.0, https://commons.wikimedia.org/w/inde...urid=107557546)
Discovered almost exactly 198 years ago by James Dunlop from the Parramatta Observatory in New South Wales, Australia, NGC 1365 is the finest barred spiral galaxy in the sky. It would no doubt have been the first galaxy in which spiral structure could have been discovered if it were farther north - or there were more astronomers with large enough telescopes in the southern hemisphere prior to the discovery of M51’s spiral structure in 1845.
REgardless, NGC 1365 is certainly the finest barred spiral I’ve seen, although my views of it from the northern hemisphere are compromised by its -36 declination. It takes an exceptionally good night to get a passably decent view, and no doubt what I’ve seen pales in comparison to what observers in the southern hemisphere have observed.
A member of the Fornax Galaxy Cluster, NGC 1365 is about 74 million light years distant. This galaxy has some exceptional properties, making observations of it all the more special. It has a diameter of about 300,000 light years, which is quite large as spiral galaxies go. Its central bar has two components – the straight long bar that the spiral arms whirl out from, and an inner, oval bar set at an angle to the long bar.
The inner bar- aka the core of the galaxy - is also its brightest part visually. Its structure may be due to a combination of instabilities in the orbits of stars near the core, density waves, gravity and the overall rotation of the disc. It also rotates more quickly than the long bar. The bars have been shown to draw gas and dust in from the spiral arms, fueling intense star formation, and to siphon this interstellar medium toward the central supermassive black hole (SMBH), playing a role in the galaxies evolving morphology.
However, the SMBH is only 2 million times the mass of our sun, making it about half the size of the one in the center of our Milky Way galaxy. Incredibly, it rotates at nearly the speed of light! Spacetime must be a tangled mess around this SMBH – and what must it look like? Mind boggling to think about.
The two spiral arms are wonderfully defined, and visually are the main attraction as they whirl off the ends of the long bar. My favorite part is how the ends of each arm curl around back toward the bar – beautiful! Photos, such as the one at the one posted above, also show that the arms are the brightest parts of a much fainter spiral disc, consisting of small spiral segments. I have not seen any of these segments, but I’ll bet they have been seen by others.
N1365_compositedrawing_C.jpg N1365_compositedrawing_C_invert.jpg
(NGC 1365 as seen through Jimi’s 48-inch f/4 at 487x. 21.48 SQM.)
My best view was through Jimi’s 48-inch scope in 2016, as shown in the sketch above, but unfortunately that was on a night of relatively poor transparency. Maybe next time the sky will be more cooperative.
NGC1365_28inch_2015_Steens.JPG
(NGC 1365 as seen through my 28-inch f/4 at 408x. 21.47 SQM)
However, a 48-inch scope isn’t needed for a satisfying view, even when the galaxy is much lower in the sky. The best views I’ve had with my 28-inch f/4 scope were from an altitude 2250 meters (at 42 degrees north latitude) and the view showed many of the features seen in Jimi’s scope. Observations through my old 20-inch f/5 Dob were decently detailed as well.
Obviously, NGC 1365 is a gem, and even a poor view can be an astonishing sight. So, give it a go, and let us know what you think about this stunning barred spiral galaxy.
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