Object of the Week May 21, 2023 - M 53 + NGC 5053 - an unusual pair of two Wukong Globular Clusters

Messier 53
RA: 13h 12m 55,2s
DEC: +18° 10? 09?
Size: 12.6
vmag: 7.7

NGC 5053
RA: 13h 16m 27,0s
DEC: +17° 41? 52?
Size: 10.0
vmag: 9.0

This "must see" pair in Coma Berenices is one of the highlights in the galaxy focus spring sky, especially when you have telescopes with fields larger than one degree and a suburban sky.

Johann Elert Bode discovered M 53 in 1775 and so nearly 250 years ago with a very simple Dollond telescope. Some years later, William Herschel was the first who resolved the cluster with the much larger and more powerful 18.7-inch speculum mirror telescope. Beside this detail, he discovered NGC 5053 in 1784 with the same telescope.

Beside the simple beauty of this pair, the birth of this two globular clusters are the most fascinating thing here. While we did not know about the origin of the GS's for sure in the past, GAIA changed our understanding fundamentally. Already the first released data sets in 2016 shows stellar streams around our milky way. This streams are signs of mergers and a product of former dwarf galaxies. And interestingly most of the GC's lies exactly within these streams.
Yuan et al. [2020ApJ...898L..37Y] found a relation between the newly discovered stellar stream LMS-1 (low-mass stellar-debris stream) and our OOTW objects. Naidu et al. [2020ApJ...901...48N] named this stream "Wukong". A former paper of Sang-Hyun Chun et al. [2010AJ...139...606] found a tidal bridge-like feature and an envelope structure around our two globular clusters and assumed that both interacts and M 53 has stripped stars from NGC 5053. But at least GAIA clarifies the membership of both.
I general, both GC's are metal-poor, old (~12 Gyr) and far away from us (M53 - 60kly, NGC 5053 - 57kly).

In the telescope, both shows a totally different face. While both are equally large, the Shapley–Sawyer Concentration Class of M 53 is a "V" while NGC 5053 has a "XI". In addition, M 53 has a much larger surface brightness. That makes NGC 5053 to a much more difficult partner to observe, especially when transparency is not the best. In return, NGC 5053 has an interesting background and shows some galaxies in larger apertures (Kafalis, 2002). But now it is your turn. What is the smallest aperture to catch NGC 5053 and can you see some of the background galaxies?

picture: Bernhard Hubl, 4"
Attachment 5130

sketch: Uwe Glahn, 4" Bino, 23x, NELM 6m5+
Attachment 5131


GIVE IT A GO AND LET US KNOW!

NGC-5053 with a 13" at 70x: "Cluster with no particular form. With a broad band filter, detected some faint haze. Spread out. Harder than some galaxies." However, with a 20" at 272x, "This was difficult. I could only see a handful of stars resolved. Must be faint and spread out. (Estimated class=?; Uranometria=11)."
M-53: 20" "Easy to find from Arcturus. Can resolve quite a few stars. The core is definitely brighter. The edges are about 1 core-diameter out and the fainter stars can be seen gradually fading out towards the edges. Estimated class = 7; Uranometria = 5)

Was not aware of background galaxies at the time.

Hi here's my observation from 2015: Messier 53 globular cluster in Coma Berenices ; magnitude: 7.7 ; size: 12' ; bright and well resolved all the way to the core.
Ngc 5053 globular cluster in Coma Berenices ; magnitude: 9.47 ; size: 10' ; slightly oval; averted vision helps to pull out some stragglers, but overall very diffuse. I used a 10mm Ethos at 198x for both with my 14.5 Starstructure f/4.3
Attachment 5134 Attachment 5135

Thanks for the enlightening OOTW post, Uwe. I did not know that these two globulars share a history.

In my 25x100, the pair makes a nice view in the same field: NGC 5053 obviously significantly lower in surface brightness than M 53, but still conspicuous from a Bortle 3 sky.

I took a "closer" look at NGC 5053 recently through my 18" telescope (March 17th 2023, fromDeath Valley National Park California, which is a Bortle 2 site but the skies had clouds and poor transparency on this night; I was chasing suckerholes). NGC 5053 appeared as a faint elongated patch that resolved into grainy texture. The patch seemed uniformly faint, and gave the sense of being fully resolved upon tacking more power. A notable clump of 2 or 3 stars forming a nearly equilateral triangle with the two stars that flank it catches the eye.

Nice write-up, Uwe. In my June 2023 Sky & Telescope article titled "Far-Out Globular Clusters", I treaded lightly on the origin of M53 & NGC 5053 by writing "While there is a high probability that M53 was formed long ago in another galaxy, figuring out more than that has proven very difficult. Nonetheless, it does seem to have a traveling companion less than 1* away and closer than 5,000 light-years away from it in space. William Herschel swept up NGC 5053 for the first time on March 14, 1784, immediately after observing M53 with his 20-foot (18.7-inch mirror) reflector."

Hopefully in the next decade scientist might be able to pin down it's exact stream origin.

Scott H.