A Globular Feast

[Mike JW]

As you know from a recent previous post I visited M13 a little while ago. A few nights ago I decided to go Globular Hunting in Oph, Ser, Sct, Sco, Aql.

Below is a Globular Montage from this fun tour.. M9 , M10, M12, M14, M107, NGC 6235, 6287, 6401, 6356, 6342, are all in Ophiuchus.

M5, NGC 6539, Pal 5 are all in Serpens. NGC 6712 is in Scutum. NGC 6760 is in Aquila. M80 and M4 are in Scorpios.  I added M13 at the end.

This tour shows the beauty and variety of these celestial gems. With each crop I have retained the same image scale.

Might be fun to do a complete tour of the northern globular clusters, including the elusive Palomar ones.

Hope you enjoy.

Mike

PS Bill kindly pointed out I had miss-labelled NGC 6235 as NGC 6285. Thanks Bill, much appreciated. Now corrected as of 20th May 2020.

 

Edited May 20, 2020 by Mike JW
NGC 6235 incorrectly labelled as NGC 6285

[Martin Meredith]

Amazing haul. These kind of comparisons are really interesting. Observing globular clusters as singletons they can seem a bit 'samey' but seeing them one after another or well laid out like you have done one can really appreciate their variety of features. Just a comparison of M9, 10 and 14 on your top 2 rows is quite revealing.

There are few enough known galactic GCs (157 as far as I am aware) that observing all those visible from one's latitude over a season is a reasonable proposition (approximately 100 down to ~ -30deg 20' ).

In fact, it would be an interesting activity to see what is the most southerly GC one can pick up with EEVA techniques. I once managed Omega Centauri but that was from the south of Spain. Rising above the sea it was an impressive sight in spite of intermittent near-horizontal light pollution from a nearby lighthouse. I will see if I can find the picture.

Martin

[Mike JW]

Thanks Martin,

I can possibly get down to -26 Dec, which gives me 82 targets - very tempted to go for them. Makes a change to chasing faint galaxies. Mike

[Martin Meredith]

Mike, I was inspired by your Pal 5 capture to have a go myself tonight during another very brief test session. It was really hard to find this one! I rotated the shot to agree with yours. This must be one of the loosest globular clusters out there, more like an open cluster really. There are quite a few faint galaxies visible through the cluster as well as quasars, including a mag 21redshift 3.73 (won't be visible on my shot). Just a screenshot tonight as the software is in an in-between state.... this is 15 x 15s, captured natively.

It would be interesting to look at the GAIA data release to see just how extensive yet sparse this cluster is. I get the feeling that there are not many more stars than are being picked up here but I could be very wrong. Certainly it has whetted my appetite to dig out some articles on this cluster.

Martin  

[Bill S]

Wikipedia does list Palomar 5 as Shapley-Sawyer Class XII (Almost no concentration towards the center.)

https://en.wikipedia.org/wiki/Palomar_5

https://en.wikipedia.org/wiki/Shapley–Sawyer_Concentration_Class

Its host galaxy seems to be doing a bit of no good. Tidal tails.

https://arxiv.org/pdf/1909.03048.pdf

 

[Mike JW]

I have just read the above articles so here is a summary.

Palomar 5 is a globular cluster (mag 11.8) about 76,000 lyrs away in Serpens and is approximately 176 lyrs across. It is being gradually broken up due to the gravitational forces of the Milky Way and also internal forces such as binary stars interacting. As it dissipates (spread out) there is a trailing tidal stream and a leading tidal star stream. These tails are long and thin and extend at least 10kpc. The leading tail is truncated compared to the trailing tail. A reason for this is not known but it could be due to the gravitational forces of the galaxy's bar. The structure of Pal 5 and its tails have been deduced from measuring the proper motion of the stars. It would appear that Pal 5 has been breaking up gradually over several billion years.

Sky Map, Sky Safari and Sky Tools 4 all give a slightly different boundary for Pal 5.

Below is an approximation of the Pal 5 boundary with a reference star labelled.

Mike

 

[Martin Meredith]

Thanks for those links Bill and that precis, Mike. When I get a little time I am definitely going to plot a GAIA figure of this cluster. 

This is a screenshot of where I am placing the boundaries based on Harris' data on GCs. It isn't very visible but the pdf is chart SER3414 if anyone has the Pretty Deep Maps downloaded. It seems to cover a wider area than our shots (the star you indicate is the brightest star in the lower-left quadrant of the GC on the chart)

My interest was piqued in part by the presence of the Abell cluster next door and also the scattering of galaxies 'within' the boundaries of Pal 5. 

[Mike JW]

Hi all,

I could not resist another look at Palomar 5, despite being low down. This time with the C11/ultrasrar. I decided to let it run for 10 minutes. I am not convinced there is significant improvement after 10 minutes. Actually the improvement in the view after about 5 minutes seems minimal.

Below is the latest shot, orientated to match the Pretty Deep Sky Map, SER 3414. The fov of the set up is not quite big enough to match the circle on the chart.

There are faint galaxies that I have identified down to about mag 19.

Also included is the Aladin view of the area.

Mike

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

[Martin Meredith]

If I may add a couple of post-prandial globulars to your feast, here are two rather understated clusters, both discovered by William Herschel, that I observed a couple of weeks back. Both have small apparent diameters (although Herschel described NGC 4147 as very bright and pretty large). I found the colour contrast rather appealing.

NGC 4147 is said to contain 23 blue stragglers. The Hubble image of NGC 4147 on its Wikipedia page doesn't look as blue as mine but nobody's perfect. It is well described in this article: https://arxiv.org/pdf/astro-ph/0508650.pdf, where the authors point out that it doesn't suffer from much reddening since it is located near to the North galactic pole.

These are live-combined 1-click LRGB captures using LAB colour space.

Thanks for looking

Martin

 

 

[Highburymark]

Thanks for these fine images Mike. They resonated with me for a few reasons.  

First because I don’t think there’s anything in the night sky as extraordinary as globular clusters. These weird, yet ancient bodies which we can only imagine being part of - what must the night sky look like from within? Each so similar yet so different.
Second because, although I’m not an imager, I do use a night vision image intensifier to pick out deep sky targets from my light polluted location - so we both belong to the same EEVA section of SGL.
And last, I’d never truly resolved a globular cluster until I tried night vision.  The first time I did so - M92 with a modest 85mm refractor - was certainly one of the most memorable stargazing experiences of my life. Then I moved on to M13 and things got even better! Until that point they had been merely faint and fuzzy. 
Must be just as thrilling to capture them with your equipment - and you have a record to share with everyone afterwards - a skill which I haven’t yet mastered.

[Mike JW]

Martin - thanks for adding to the post and in colour. I recently visited 5634 but my focus must have been out so the shot is only worthy of the bin.

Anyone else reading this thread - feel free to add in globular shots.

Mark - Globulars are always worth a look and I never loose the sense of awe and wonder when viewing these objects. Yes I do get a thrill at capturing them and the more you look the more one appreciates the subtle differences. I am hoping to capture as many as I can over the year and then to do a grand post. It makes a real change to picking up faint fuzzies. 

I would love to give NV a go but the expense............

Have fun and thanks for your thoughts and comments.

Mike

[Bill S]

Globular Clusters in Ophiuchus.

Inspired by Mike JW's feast I had a bit of snack myself at the end of May. One of the courses was in Ophiuchus.

Messier 10 is class VII (Intermediate loose concentration), M12 is IX (Loose towards the centre) and M14 and M19 are both designated VIII (Rather loosely concentrated towards the centre).

Palomar 15 is by my reckoning class XII (Almost no concentration towards the centre) and is more a case of spot the globular cluster. I can't really see it clearly in the Aladin picture posted at the end.

Just a single 15 second gives a reasonable snapshot. A stack of 10 is below and does not show a lot more.

 

 

 

 

Spot the globular cluster time...

 

 

Best regards

Bill

 

[Mike JW]

Great. A decent snack! I note the comment re no real gain with stacking. I find the same when viewing globulars. I tend to then go for short subs in the hope keeping stars sharp. Mike

[MarsG76]

Nice harvest of different variety of globbies.....

 

[Martin Meredith]

We seemed to be having issues with some Palomar GCs in this thread but the other night I came across one that is far from faint. This is Pal 8 in Sagittarius. The left is a single 10s sub while the right is an LRGB combination (about 40s in each filter). This one is set in a wonderfully starry field and I imagine it is easier to spot than some of the other Palomars as it is both compact and relatively bright (though not the most compact nor the brightest of the Palomars).

 

Reading more about them it seems they do cover a wide range of visibility. Indeed, 3 of them are among the 6 most distant 'halo' clusters in our galaxy. Spotting all of them I think would be an interesting challenge and fortunately for northern observers the lowest declination is -26 (Pal 6 in Ophiuchus) [the Palomar sky survey only went to -27 dec].

Pal 8 was discovered by George Abell

 

The paper contains the remark: "Six of the new clusters, Nos. 1, 3, 4, 5, 12, and 13, are inconspicuous and barely recognizable because of their great distance. However, plates obtained with the 200-inch telescope by Sandage reveal that they are bona fide globular clusters."

Pal 8 is regarded as a highly-reddened cluster. Here's a longer stack (I added a lot of luminosity subs; the colour is still 1 minute of each apart from blue which seems to have sneaked in an extra minute) zoomed into the central region with the colour saturation turned up a little. Presumably the whitish star at the top is a much closer foreground star.

 

cheers

Martin

Edited August 23, 2020 by Martin Meredith

[Mike JW]

Hi Martin, great to see some more globulars being added to this thread, especially the palomar globulars. I had contemplated trying to get the numerous sagittarius globulars but anything below -20 Dec is tricky for me from GB.

[Mike JW]

I have just transferred my Pal 12 info from a separate post to keep this thread going with globulars.

Palomar 12 at -21 DEC is too low for anything worthwhile but here is my attempt from last night (Aug 18th). It lies about 62,000 lyrs away and is about 52 lyrs across. It is a relatively young globular cluster. Its proper motion indicates that it may have been captured from the Sagittarius Dwarf Elliptical galaxy about 1.7 billion years ago. Below my poor shot is the Hubble image.

[Mike JW]

Here is my recent observation of Pal 13. Not exactly a bright globular! I was uncertain whether I had located it at first as it is dim.

Mike

Notes:

Palomar 13 is one of the least luminous globulars in the milky way. The gravitational behaviour of globulars clusters can be explained by the intense gravitational forces within such a cluster. It has been suggested that there may be dark matter associated with globulars but this is not needed to explain the globular dynamics. However, in the case of Pal 13 the star velocities are not quite as would be expected, suggesting that there could possibly be dark matter present in this rather extended globular. Some analysis suggests that 95% of the globular mass is not luminous, implying dark matter. However, if I have understood correctly the presence of unresolved binary stars and associated mass is yet to be fully determined and may have a bearing on the amount of proposed dark matter or whether dark matter is needed at all to explain the cluster dynamics. It also appears that this globular is at its peak of breaking apart (dispersion) as it orbits the milky way in a rather eccentric orbit. The stragglers ejected from the cluster are blue in colour. Pal 13 is also a low mass cluster.

 

[Martin Meredith]

Here's a globular that is not so much dim as a little hard to spot (not helped that I didn't centre it as I was not sure whether I had it in the field or not...).

 

I also had trouble finding it in the catalogues as I have it by its previous name. This is nowadays known as AL3 after Andrews and Lindsay who discovered it in 1967, although it was initially believed to be an open cluster. It was only confirmed as a globular cluster in 2006 as described in this paper: https://arxiv.org/pdf/astro-ph/0606718.pdf. In fact, I needed to check their Figure 1 to ensure I had the right spot.

This is located in the inner bulge of our galaxy and was only identified/discriminated from the stellar field due to metallicity differences. 

Here's a zoomed and oriented version to match their figure. The resolution I'm getting is so much poorer than the 1.54m scope they used.... But seriously, what look like individual stars in my image are often amalgams of several.

 

Martin

 

 

[Mike JW]

I had not realised that globular clusters could be so far in toward the central bulge. Always something to learn. Well done for tracking this one down. Mike

[Bill S]

Fascinating stuff. There have been a few more of these bulge globular clusters discovered. https://phys.org/news/2019-06-ancient-globular-clusters-galactic-bulge.html

Very old objects up to 13.5 billion years old! Thanks for drawing attention to them, Martin. Like Mike, new stuff to me.

Sagittarius is not a good area of the sky for me so I really enjoy seeing others' observations. 

[Martin Meredith]

Thanks for that link Bill. I'll take a look tomorrow. Meanwhile the scope is cooling...

Thanks Mike. I'd like to pretend I was out seeking this cluster on purpose but it was purely accidental that I came across it near another object I was looking at and the name was sufficiently unusual to let it pass by.

I'm fortunate to get a reasonable view of Sagittarius here. I spent much of the session observing planetary nebulae thereabouts of which there are 100s in Sagittarius, though mainly too faint for me, and those that are sufficiently bright are hard to find amongst the star fields -- fun though! Tonight I'm hoping to spot some PNs in Aquila instead. The moon is too close to Sagittarius for comfort.

Edited August 25, 2020 by Martin Meredith

[John]

These distant and ancient clusters are fascinating. I tracked down NGC 2419 back in March this year:

 

[RobertI]

Fascinating post, a cornucopia of GC information, great idea @Mike JW to show these globs at the same image scale to highlight the variety.

[callump]

Palomar 13 in Pegasus last night - one exposure did not make the grade 17x20s.
(C11, G11, 0.63FR, ASI174MM Mini. Bias and dark subtraction)

It was by far the hardest of those objects that I actually found, and spent quite some time confirming this was the right place.

 

Callum