Object of the Week, Dec 3, 2023 – Arp 258 and Hickson 18 = VV 143 in Aries
R.A.: 02h39m06.1s Dec.: +18°23'02"
Size: 1.7'x 0.8', Magnitude: 15.50 B
(I’m filling in this week for Dragan as he is busy drinking margaritas in Mexico)
I will tell you right off that these guys are stinkers, even though they appear in both the Arp and Hickson catalogues… but Arp 258 is not quite the same as Hickson 18!
Look at this labeled chart, borrowed from Alvin Huey’s “Hickson Group Observer’s Guide”…
… and note that the galaxy labeled “A” (MCG+03-07-038, PGC 10046 and others), is a part of Hickson 18 but apparently is not part of Arp 258, which is the faint train wreck heading off towards the northwest centered only about 1.5 arc-minutes away. These (3) galaxies have designations of UGC 2140 A, B and C from south to north.
Here is what Paul Hickson had to say about this group… “Group 18, also known as Arp 258 or VV143, consists of a background galaxy (A) and a line of three irregular objects apparently in contact. At present [1994] no redshift is available for the brightest of these. These three objects may simply be a concentration of star and gas within a singular irregular galaxy, or they may be the result of an interaction between two or more low-mass galaxies”.
We know now that the 3-smudges Arp 258 trio has a redshift indicating a distance of about 175 million light years whereas galaxy A is a whopping 445 million light years in the background, so it is clearly just a line-of-sight coincidence.
This is the best photo I could find of the area, from the late astrophotographer Rick Johnson (RIP Rick), here…
… and you can see that there is a lot going on here and it is hard to discern much in the way of details, and that there is a lot of fluff in the area… just not in my eyepiece!
Read what Rick has to say about these galaxies here at his webpage, it is really an interesting read… and he was even able to identify several asteroids in his astrophoto!
Halton Arp puts this group of galaxies in his “Irregular clumps” category and it easy to why! In my 25” f/5 Obsession I could easily see the “A” galaxy, PGC 10046, but the other guys were just a dim smudge in the eyepiece and there is no way that I could discern individual objects. This is not an object for the faint of heart!
As always, give it a go and let us know
Last edited by Paul Alsing; December 4th, 2023 at 05:20 AM.
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