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View Full Version : Object of the Week, March 19, 2023 – NGC 2648 = Arp 89



Steve Gottlieb
March 19th, 2023, 06:56 PM
Name: NGC 2648 = Arp 89 = KPG 168A = UGC 4541 = MCG +02-22-005 = CGCG 060-035 = PGC 24464
R.A.: 08h 42m 39.9s
Dec.: +14° 17' 09" (2000)
Con: Cancer
Type: Sab
Size: 3.2'x1.1'
Magnitudes: 11.9V, 12.8B; Surf Br: 13.1 mag/arcmin²

NGC 2648 was discovered by William Herschel on 19 Mar 1784, near the start of sweep 177. His description reads, "Faint, small, with a nucleus. I had some doubts but 240 confirmed the reality." He swept the area again two years later (nearly to the day) and logged "Faint, little extended from north-preceding to south-following, considerably small. Almost like two joined together." John Herschel reported from South Africa that it appeared "pretty bright; little extended; pretty suddenly much brighter middle; precedes a star 10th magnitude."

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Despite William's comment "Almost like two joined together", I don't believe he noticed the small edge-on companion to the southeast. But R.J. Mitchell, Lord Rosse's assistant, made an observation on 23 Feb 1857. He clearly sketched a second nebula (Alpha) and noted, "I think Alpha is a very faint ray though likely to be taken at first for a star." The diagram shows CGCG 060-036 = MCG +02-22-005 as a small nebula extending WNW-ESE. Unfortunately, the full description and sketch was not included in Lord Rosse's 1861 monograph, so John Herschel was unaware of the companion when he compiled the General Catalogue (GC) in 1864 and Dreyer skipped CGCG 060-036 in the NGC.

Halton Arp included the interacting pair as Arp 89 in his 1966 Atlas of Peculiar Galaxies, under the classification "Spiral galaxy with large high surface brightness companion on arm." The pair is also known KPG 168 from the Karachentsev Isolated Pairs of Galaxies Catalogue.

This image from the 200-inch at Palomar is in the Atlas, but the second image from the HST displays the spiral arms much better.

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In my 24-inch, NGC 2648 appeared moderately or fairly bright, elongated 5:2 NW-SE, ~1.5'x0.6', sharply concentrated with a very bright core. An 11th magnitude star lies just under 2' east of center. The companion is faint, small, elongated 5:2 WNW-ESE, ~25"x10", low even surface brightness.

Back in 2012, I had a look through Jimi's 48-inch and NGC 2648 extended nearly 2.5' in length. The large, very bright core increased to a stellar nucleus. The galaxy had an asymmetric appearance with the south-southeast arm stretched into a faint tidal tail. The brighter portion extended in the direction of the major axis, but a faint thinner tail curved east, fading out just before connecting with CGCG 060-036. The companion was quite thin -- 1.0'x0.2' -- and sharply concentrated with a very small, bright nucleus. I only had hints of its tidal extension to the east.

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A 6-inch scope will certainly show NGC 2648, but what aperture will reveal the disrupted companion CGCG 060-036?

As always,

"Give it a go and let us know!
Good luck and great viewing!"

Clear Skies
March 20th, 2023, 10:07 AM
A nice pair in which larger apertures ought to be able to pick out a bit more detail than I did with my 14" SCT in February 2019, under the skies of the French Ardennes (168x / 29'):


Both galaxies are visible.

The NW galaxy NGC2648 is a NW-SE elongated glow, quite suddnly brighter in a relatively large, oval core that is elongated in the same direction with a bright nucleus that is visible without AV.

The SE galaxy MCG+02-22-006 (PGC24469) is at the limit of visibility with AV, a WNW-ESE elongated glow, no detail visible. To the NNW is a mag. 11 star.

Ten years earlier under Dutch skies, using a 12" SCT I was only able to glimpse the NGC galaxy (235x / 26'):


Only the NGC galaxy is visible: A NW-SE elongated patch, brighter in the middle with a relatively large, bright core and a bright nucleus.


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Click here (https://clearskies.eu/csog/downloads/dsfootw2023#12) to download.

lamperti
March 20th, 2023, 11:46 AM
Saw this with a 13" at 240x back in 1993:"This one is a lot easier to find. It has a definite elongation to it and a slightly brighter core. Next to 2 faint field stars."

Steve Gottlieb
March 20th, 2023, 11:36 PM
Both galaxies are visible.

The NW galaxy NGC2648 is a NW-SE elongated glow, quite suddnly brighter in a relatively large, oval core that is elongated in the same direction with a bright nucleus that is visible without AV.

The SE galaxy MCG+02-22-006 (PGC24469) is at the limit of visibility with AV, a WNW-ESE elongated glow, no detail visible. To the NNW is a mag. 11 star.


Nice observation! I was guessing a 12" to 14" would reveal the companion MCG +02-22-006 in good conditions.

Uwe Glahn
March 27th, 2023, 05:51 PM
Very nice pair Steve.

I got two observations, one with a 20-inch and the second with the 27-inch under better conditions.

While the 20-inch shows the companions easily as a 1/3-1/4 streak but without a connection to 2648, the 27" indicates a thin and faint bridge.

sketch: 27", 293x-419x, NELM 6m5+
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home (http://www.deepsky-visuell.de/Zeichnungen/NGC2648.htm)