Object Of The Week June 4, 2023 - NGC 5634

[wvreeven]

NGC 5634

Globular Cluster

Virgo

RA: 14 29 36.4
DEC: -05 58 27

Mag: 9.47

William Herschel once again is the discoverer on an OOTW object. But the discovery wasn't without issues. When he found this object the first time, he was sweeping through Virgo in the night from April 24 to 25, 1784, using his 18.7 inch telescope and he recorded this cluster as last of 16 new objects discovered that night. It was noted down as VI 8. However he made a mistake noting down the position and later it was noticed that that was the same position as II 190 (NGC 4928). Less than a year later, on March 5, 1785, he noted it down again as I 70, this time at the correct position.

5156
NGC 5634: Only globular cluster in Virgo. Section of PanSTARRS DR1

The cluster is the only globular cluster in Virgo and lies 1.3' west of the magnitude 7.94 K3III giant HD 127119 and has Shapley–Sawyer Concentration Class IV, making it intermediately rich in concentration towards the centre. NGC 5634 likely once was a member of the Sagittarius Dwarf Spheroid Galaxy.

So far I have only observed this globular cluster with my old 15 cm Newtonian telescope. I noted down from my observation of it on July 9, 2008, in Southern France: "Visible as a small, round glow. No bright centre but it does have faint outer regions. The centre has a uniform brightness." Apparently I wasn't able to resolve stars in it. I'll need to look this one up with my 12" and 20" telescopes.


As always,

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

[lamperti]

I've observed this one twice, with a 10" & a 20". With the 10" at 117x "No resolution. Round, bright. Adjacent to a star." But with the 20" at 272x:"Easiest one of the night. It is adjacent to a bright star. It starts to resolve and is fairly homogeneous, concentrated and some fading around the edges. Possible a Class IV-V. (really = Class IV)."

[Raul Leon]

Hi, here's my observation from 4/28/2009: Ngc 5634 globular cluster in Virgo ; magnitude:9.5 ; size: 5.5' ; fairly bright; unresolved halo, brighter towards the center; located within a triangle of stars ; I used a 10mm Radian at 198x with my 14.5 Starstructure f/4.35157

[Don Pensack]

This one has a huge spread between its overall integrated magnitude of 9.5 and the magnitude of its horizontal branch (17.8)
In 32cm, in near perfect seeing, the outer edges become grainy (as from incipient resolution), but I cannot reach the horizontal branch.
As Raul's drawing shows, the core is a large % of the visible cluster.
I'd love to see this in good seeing with 80-85cm.

[Steve Gottlieb]

With 120cm at the relatively low power of 375x --


48" (5/10/18): Beautiful globular cluster with 50 or more stars resolved at 375x. Several streams or chains of stars (many easily visible) extend out of the central region, which is densely packed with faint stars over a bright, mottled background glow. A few dozen very dim stars were constantly sparkling in and out of visibility so it wasn't possible to make a decent star count. A very bright orange field star (mag 7.9 HD 127119) is superimposed in the halo on the eastern side [1.4' ESE of center]. Three additional brighter stars in the halo are on the west and north side [incl. a mag 11.9 star 1.7' NW of center] form a semicircle or crown, partially encircling the halo. The diameter was roughly 4', though the outer halo was scraggly without a distinct edge.

I seem to recall this was a "warm-up" object before dark adaptation, and I'm sure at higher power (at least 610x), the resolution would have been much more extensive.

[Howard B]

I have one observation from late August, 1993 (with my old 20-inch Obsession) when the globular was low on the western horizon:

"Neat globular - rather large and showed a hint of resolution at 182x and averted vision. Embedded in a triangle of field stars, this too was very low and I watched it set behind the trees at 182x - very cool!"

I'd just observed NGC 4866 only 3 degrees above the western horizon where I commented "this is really clear air!"

[ScottH]

Three comments, Wouter.

First, this 84,700 light-year distant globular star cluster would be visible in my 7x35 binocular if it weren't for the magnitude +8.0 star just southeast. Instead, it's only 8x56 visible.

Second, in my feature article on "Remote Globulars" in the current June issue of S&T, I wrote that "Only in the previous two decades have we gleaned that NGC 5634 is likely an orphan from another galaxy. Scientists attribute the cluster's origin to a dwarf galaxy dubbed Gaia-Enceladus, one of several remnants of a past galactic merger with the Milky Way, the earliest and most massive known to date."

Third, NGC 5634 is currently the only confirmed globular in Virgo. I say that because at the moment, Koposov 1 (https://en.wikipedia.org/wiki/Koposov_1) is only a possible globular cluster.

Scott H.

[wvreeven]

Scott, thanks for your comments.


Second, in my feature article on "Remote Globulars" in the current June issue of S&T, I wrote that "Only in the previous two decades have we gleaned that NGC 5634 is likely an orphan from another galaxy. Scientists attribute the cluster's origin to a dwarf galaxy dubbed Gaia-Enceladus, one of several remnants of a past galactic merger with the Milky Way, the earliest and most massive known to date."

I just read your article in Australian Sky and Telescope! That's great to know. Would you mind sharing your source for this?


Third, NGC 5634 is currently the only confirmed globular in Virgo. I say that because at the moment, Koposov 1 (https://en.wikipedia.org/wiki/Koposov_1) is only a possible globular cluster.

Clearly another case of poor research from my side.


Thanks, Wouter

[ScottH]

Scott, thanks for your comments.

I just read your article in Australian Sky and Telescope! That's great to know. Would you mind sharing your source for this?



Wow, I didn't know I was such an international star!

Bellazzini, Ferraro, and Ibata (2002) (https://ui.adsabs.harvard.edu/abs/2002AJ....124..915B/abstract) were the first of many papers to suggest that NGC 5634 is a "stolen" globular while Malhan et al (2022) (https://ui.adsabs.harvard.edu/abs/2022ApJ...926..107M/abstract) along with several recent papers indicate that it came from Gaia-Enceladus.

Scott H.

[akarsh]

The only observing report I have of this object comes from perhaps the year 2005 or 2006, when I used to observe with a few friends using my 8" f/8 telescope from the variable skies of southern India. My online log reads:
"This is a strangely misplaced object - globulars are found in the Milky Way core, or in an orbiting galaxy, but this is found in the opposite direction! Quite bright. Found by a friend."
I guess, this shows a teenager's lack of understanding about the galactic halo as a place where globulars can be found. Also back then, "Quite bright." was as much as I logged!

But I wish to contribute a much more interesting incident. From my experience interacting with him, I've found Steve Gottlieb to have a very remarkable memory for NGC object designations. So sometimes I like to quiz Steve just to watch him in action. Last week several of us forum members had gathered in northeastern California for the Golden State Star Party 2023: Steve Gottlieb, Jimi Lowrey, Howard Banich, Paul Alsing and myself; 5 out of our 12 OOTW authors! Friday night was the night of the raffle, and everyone got a raffle ticket either with a number ending in the 5000s or the 8000s. Obviously, the 8000s numbers were no fun because it was beyond the NGC's ~7840 entries. I walked down and sat next to Steve to quiz him about the 5000s numbers, starting with my own raffle ticket. "Steve, what's NGC 5634?", I asked him. His response, although in a playful taunting tone, took me aback a bit -- "Are you kidding me? You should be ashamed of yourself!" :D :D. Turns out we had just discussed this OOTW thread several hours earlier that evening, and I had failed to connect NGC 5634 to be the globular in Virgo and the object of the week! :)

Anyway, the Object Of The Week has got to be a lucky raffle ticket, right? I did win! Unfortunately, what I won was an SCT micro-focuser; I'll now have to find someone going over to the dark side so I can trade it for a Dobsonian focuser!

Lucky NGCs and Clear Skies,
Akarsh

[Uwe Glahn]

Very nice glob. I noted with the 27": cute picture, very nice glob framed by a sharp triangle, some stars visible already in the searching eyepiece; with 419x dozens of stars, but not fully resolved, hardly concentrated; nice small triangle at the western side