Object of the Week, NGC 1316 = ARP 154 = Fornax A

[Paul Alsing]

Object of the Week, NGC 1316 = ARP 154 = Fornax A

R.A.: 03 22 41.7 Dec.: -37 12
Size: 12.0'x8.5', Magnitude: V 9.4
Fornax


NGC1316_Joseph Drudis.jpg

Photo by Joseph M Drudis

NGC 1316 is the brightest of the 58 members of the Fornax Galaxy Cluster, also labeled as AGCS 373, and is about 2.4° SW of the mighty barred spiral NGC 1365 at a distance of about 62 million light years… although this figure still being debated. At the eyepiece it is just another big and bright giant elliptical galaxy with a small spiral companion, NGC 1317, only 6 arcminutes north, a nice pair in the eyepiece. However, there is more to this story. NGC 1316 has had a violent history!

While doing my due diligence regarding this OOTW I have learned quite a lot about this pair. It is probable that although NGC 1316 has a size and a shape common for elliptical galaxies, it also has dust lanes and a disk more frequently observed in spiral galaxies, so it is speculated that it is the result of a rich history of merging events over the last 2 or 3 billion years. Its nearest companion is NGC 1317 (mag 11.9), and it is about 100,000 light years distant (center-to-center) and will almost certainly be the next victim of this “Galactic Killer”. A third galaxy, NGC 1310 (mag 12.6) lies about 21 arcminutes WNW. 30 arcminutes ENE of NGC 1316 is a mag 14.4 lenticular galaxy that Megastar labels as NGC 1316C, and about 21 arcminutes NNE of NGC 1316 is a trio of small galaxies, the southern pair being labeled by some sources, for example, as NGC 1316A and NGC 1316B. Very curious and not at all intuitive to me. It seems these to me that these “A”, “B”, “C” etc. suffixes to NGC numbers are never “official”, unless someone has evidence to the contrary.

Here is a copy-and-paste of the area from Megastar (the big circle is 1/2 degree). With a low-power eyepiece using my 25” f/5 Obsession I can see the 3 brightest galaxies in the area within the same FOV.

NGC1316 Megastar.jpg

NGC 1316 is also known as the radio source Fornax A, and it is the 4th brightest radio source in the entire sky, with radio lobes extending over several degrees of sky, perhaps 10 or 15 times the size of the visible galaxy itself. Dr. Arp included NGC 1316 as #154 in his Atlas of Peculiar Galaxies in the “Disturbed with interior absorption” category, which basically means that they have “dark dust lanes that obscure part of the disk of the galaxy”.

As always, give it a go and let us know.

[akarsh]

My only log entry is from October 1st 2006, using my old ATM'd 8" f/8 from a site at a village north of Bangalore, India:

"Large, bright, elliptical patch of light showing much brighter middle. Spotted in astronomical twilight. Interesting. Adds to my list of `A` radio galaxies: Cetus A, Fornax A, Virgo A, Ursa Major A, Centaurus A"

My notes mention NGC 1326, but carry no mention of NGC 1317. I had no idea this is a shell galaxy with interesting structure until this OOTW.

[Howard B]

I also have only one observation of NGC 1316, this with my 28-inch f/4 scope from 2017 at Chickahominy Reservoir. This was an excellent sight given its low altitude from 43.5 north latitude:

"This bright galaxy is just a few degrees above the horizon, but even so the view is quite good at 155x and 408x! At 408x a dark lane is seen with averted vision and the galaxy has an overall oval shape. NGC 1317 is nearby - smaller, but still bright with a bright core. 21.68 SQM."

NGC 1316_1317_b.JPG NGC 1316_1317_b_invert.JPG