Object of the Week, April 7th 2024 -- Omega Centauri (NGC 5139)

[akarsh]

NGC 5139 = Omega Centauri = GCL 24
Globular Cluster in Centaurus
RA: 13 26 47
Dec: -47 28 51
Mag: 5.3
Size: 55 arcmin

Well, this week I'm escaping from trying to write a good OOTW. You can guess why: tomorrow is the much awaited total solar eclipse in America! I also decided against trading spots with others, because as far as I know 6 of the 12 OOTW writers are within 500 miles (800 km) of me, either trying to travel to the eclipse, or lounging with family on the eclipse line, or trying to organize eclipse events, or frustratingly refreshing the weather forecast to figure out where to go or what to do. I have an 8 hour drive ahead of me. Maybe I'll come back and do some more research on Omega Centauri and fill in some details here, but I didn't want to break the OOTW thread.

Can you believe that Omega Centuari has not been featured as a OOTW? Omega Centauri is the biggest globular cluster in our galaxy. Surprisingly, Wikipedia says that it was first identified as being non-stellar by Edmund Halley in 1677. However, it looks fuzzy to my eye very prominently every time I've seen it. Omega Centauri is thought to be the disrupted core of a dwarf galaxy and may harbor an intermediate-mass black hole at its center.

I can remember two observations of this object that are etched in my memory. Even through the light-polluted skies of a then much smaller Bangalore, India, I was able to clearly see this as a fuzzy spot from my rooftop with the naked eye on transparent nights. My most mindblowing experience was when I first pointed my 17.5" telescope at it. Back then, nobody I knew owned such a big telescope, so my friends and I had only lived through the vicarious experience of US amateurs, especially one Mr. Gottlieb. We were absolutely amazed by the burst of stars that covered the entire eyepiece, a view that never fails to impress folks even today at star parties in south India. Coming to Texas, this is one of the star objects of Texas Star Party, as amateurs living in northern USA find this to be the highlight of their trips to the lower latitudes of Texas during the summer months. But Californians need not despair, I've enjoyed views of this object from my local observing site where it is not too high above the horizon. Yet, it is so bright that it is visible to the naked eye that low.

If you've never made a trip to the more southern latitudes needed to view this object, it should be on your calendar sometime. In that case,
GIVE IT A GO AND LET US KNOW!

Clear Skies
Akarsh

[wvreeven]

First time I saw Omega Centauri was from Socorro, New Mexico, when I was an undergrad student visiting NRAO for work with the VLA in 1998. I have seen it naked eye at about 1º above the horizon from mid-Spain. And with both my 12" and 20" telescopes in Chile this is an amazingly spectacular oval of stars with two dark features in it. Truly spectacular!

[lamperti]

From Maui (7/7/1997) and Hawaii (7/12/1997). Naked eye. Large glow in 10x50 binoculars; much bigger than M-13.

[Raul Leon]

Hi here's my observation from 3/24/2017 : Ngc 5139 globular cluster in Centaurus ; aka Omega Centauri ; magnitude: 3.68 ; size: 45' x 37' ; the largest and brightest of all globular clusters ; this object is amazing even though it only transits my observing sky at 14 degrees, it has two dark areas at the bottom known as the footprint. I used a 21mm Ethos at 115x with my 14.5 StarStructure f/4.3
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[wvreeven]

A paper about Omega Centauri was published on ArXiv today. The paper is about a very detailed study of nearly 1.4 million stars in the cluster and discusses the proper motion of the stars and the rotation of the cluster. See https://arxiv.org/html/2404.03722v1

[cloudbuster]

The best view I had of Omega Centauri was from Namibia in 2022. I decided to sketch it at the lowest possible magnification (Nagler 31mm), to seemingly shrink the cluster to somewhat acceptable proportions… Sketched with a 16? Dieter Martini @58x.

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[Uwe Glahn]

Hi Akarsh,

nice write up and great OOTW.

Last time I visited NGC 5139 was only a few day ago, you know from where. In Jimi's 48" we looked at the glob with around 287x and we were IN. With bad seeing it looks like we all were drunk and 17000Lj closer to the GC.
With the naked eye the glob looks like a washed out and somewhat diffuse star.
Definitely always a cool thing to see that object as a mid European.

[kisspeter]

I can contribute a 4" observation from 2012, Hakos, Namibia (40x, 1.8° field).
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I almost forgot to draw NGC 5139 on our first trip to the south. So I was in a hurry to get it done. And I managed to mess up the starfield and had to erase about 1/3 of the field and redraw (shift) it. Also, I wasn't sure if the final drawing resembled the eyepiece view. But a couple of years later I saw that I was not so much off.

Very spectacular already with a 4". I can't even imagine what it can look like in a 48".

[Daniel_Sp]

Hi all,

I have only a sketch that was made from binocular (35mm diameters, 12.5-times magnified) observations from Waikiki Beach, Honolulu, Hawaii from 2017:

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