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View Full Version : Object of the Week, May 17th Palomar 5



obrazell
May 17th, 2020, 08:28 AM
Palomar 5
Serpens Dwarf

R.A.: 15h16m05.0s
Dec.: -00°06'42" (2000)
Magnitude: 11.80
Size: 3.2'
Concentration class XII

By mid-May astronomical twilight no longer occurs here in northern latitudes and won’t now until mid-August. However,
for those that do still get some astronomical darkness this week’s object should be an interesting one. As is well known
to this group researchers studying the newly completed POSS survey in the1950’s as well as finding lots of new
planetary nebulae and galaxy clusters there were also some 15 faint globular clusters found. Lack of checking meant
that some of these, such as Pal 7 and Pal 9, had already been found by the NGC/IC observers but the majority were
new. Pal 5 in Serpens Cauda, sometimes also known as the Serpens Dwarf as it was earlier thought it might be a
galaxy and given a UGC number, was first discovered by Walter Baade in 1950 and independently rediscovered by
Wilson in 1955. It has proved to be of considerable interest because it is a typical metal poor halo cluster that appears
to be in the process of tidal disintegration. Deep images show trails of stars both leading and trailing the cluster and
which form a stream perhaps 30000 light years long containing perhaps 5000 solar masses worth of stars.

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Pal 5 is perhaps 21 kpc from us and maybe 17kpc from the galactic centre and is currently high above the galactic plane.
It may well be currently at its further point in its orbit from the Milky Way (apocenter?) and has obviously undergone
many disk passages in its life time, and its next one may be its last before it is totally disrupted.

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It has been suggested that Pal 5 may have lost up to 90% of its mass during these crossings and now the tidal tails
stretch 10 degrees across the sky. Unlike most globular clusters Pal 5 does show a considerable amount of flattening.

Palomar 5 is not going to be an easy observational target as, with a concentration class of XII, it will appear like a very
faint open cluster.

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However as always with these objects observing conditions and object altitude may make what is hard from one
location easy from another. This is also a plea that when reporting observations please give some account of the
observing location and sky conditions as what may be easy from 2000m in mountain skies is probably not going
to be visible from sea level. This can be seen in the fact that that the NSOG Vol 2 suggests it is a target for 20/22 inch
telescopes whereas the Interstellarum Field Guide suggests it may be visible in a 12” and there are reports of seeing
it with a 16”.

Bertrand Laville
May 17th, 2020, 02:25 PM
Hi All,

I observed this faint target a dozen years ago, from southern Alps, in a rather good sky: SQMZ 21.72, NELMZ 7.0, seeing average.
The altitude of the cluster was 41° above horizon, and the power I used was 240x and 312x, with my 25" Obsesssion.

The object has not been seen as a star cluster, but only a faint patch with hazy limits.
With a long observation, I could perceive 5 or 6 stars in direct vision, and about 25 with adverted vision,none of them spotted with precision.

All in all, Pal 05 is, according to me, "beyond" the 25" scope. Perhaps Jimmy with its 48"...
http://www.deepsky-drawings.com/pal-5/dsdlang/fr

Clear sky
Bertrand
http://www.deepsky-drawings.com/


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Bertrand

wvreeven
May 17th, 2020, 03:40 PM
My observation from July 10, 2015, from SQM 20.9 skies reads:

At 320x I see a few very faint stars where Pal 5 is supposed to be. At 151x I occasionally see an incredibly faint glow.

Uwe Glahn
May 17th, 2020, 03:45 PM
Wow, nice information Owen. And indeed a difficult object. I add my observations with the extra information about the observing place.

4" Bino, 23x, fst 6m5+ (Sudelfeld, Pre-Alps, 1300m)
not visible or suspected even under good transparency

16", 51x, fst 6m5+ (Stumpertenrodt, low-mountain-range, 420m)
first try together with Martin Schoenball, we both see somewhat faint but in wrong position, negative observation

16", 69x, fst 6m5+, (Sudelfeld, Pre-Alps, 1300m)
under good sky the best view with 5,8mm AP; also with max. AP (7,8mm), not successful with 4mm AP; stands between one 9mag and one 11mag star; visually as a round, 6' large, very faint spot of light; 3-4 stars glimpsed out between the GC, can hold GC with averted vision

16", 51x, fst 7m0, Bieler Höhe, Alps, 2000m
finally, seen under very good sky conditions; nevertheless extremely difficulty to detect; only with max. AP, large, circular wisp of light NW a mag 9 field star

27", 113x-293x, fst 6m5+, (Sudelfeld, Pre-Alps, 1300m)
easy visible with averted vision and 113x, borders of GC clearly detectable, somewhat mottled structure within the GC; with 172x more mottling and similar visibility of the borders; from 293x up several stars within the GC, the GC itself disappears

sketch: 16", 51x, fst 7m0, Bieler Höhe, Alps, 2000m
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lamperti
May 17th, 2020, 07:14 PM
I have observed this only once in 1998, with an 18" at 256x, from a suburban-rural location with poor seeing and mediocre transparency: "Looks like a faint galaxy. No resolution."

Ivan Maly
May 17th, 2020, 09:18 PM
Excellent write-up, Owen. I am pretty sure I've reobserved it more recently, but here is my record from 9 years ago (16", typical SQM for site 21.6, elevation 700 m, 42 N): "Pal 5 – at 225x, several members held, several more flicker in and out."

Jimi Lowrey
May 21st, 2020, 08:13 PM
I revisited Pal 5 last night. At 375X the cluster was resolved. It looked more like a open cluster than a glob. I noticed on my computer screen that there was several faint background galaxies behind the cluster so I decided to give them a try.

First I observed SDSS J151551.71-001046.6 it was extremely faint and at 813X was averted vision only
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I then tried 2MASS J15160056-0009434 at 813X I could hold it 100% of the time it was a small elongated glow.
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Last but not least was LEDA 3112086 at 813X it was direct vision glow with a brighter core. What is interesting is that although it was the brightest of the 3 it has a Z=0.1033 which gives it a light travel time of 1.3 billion light years.
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I had a fun time tracking down these faint galaxies and noticed today that there are a few more that I can try.