Object of the Week May26th, 2024 - NGC 5466

[obrazell]

NGC 5466

Globular Cluster

Bootes

R.A. 14h05m27.0s

Dec. +28°32'06" (2000)

Magnitude: 9.20

Size: 9.0'

Class XII

With astronomical dark now gone from my latitude until mid-August I am now restricted to
brighter objects such as globular clusters. I was surprised that my choice this month had
not been selected before for the OOTW. NGC 5466 is a globular cluster in Bootes first
discovered by William Herschel in 1784 who catalogued it as H VI.9. It is a loose class XII
cluster that is often thought of as one of the more difficult NGC globular clusters to find
because of its openness, beaten only by NGC 5053 in Coma.

5457

It is thought to have joined our galaxy as part of the Sequoia merger about 10 billion
years or so ago. NGC 5466 has a stellar stream associated with it called the 45 degree
tidal stream which will be stars stripped from it due to passes through the Milky Way plane.
NGC 5466 is listed as about 51000 light years from the earth and about 52000 from the
centre of the Milky Way. As expected, given its age, NGC 5466 is very metal poor which
gives it a suggested age of about 12.8 billion years. The remaining mass in the cluster is
estimated to be only about 54000 solar. The tidal streams and mass make it very similar
to Palomar 5. It is suggested from modelling data from the GAIA EDR 3 survey that the
tidal stream from NGC 5466 may have been perturbed by the LMC. Given the habit by
imagers to rename everything apparently NGC 5466 is now also known as the Snowglobe
cluster. NGC 5466 is also unusual in that it contains a blue horizontal branch. Hubble did image
NGC 5466 in 2019 as part of a program to measure the motions of stars in Globular clusters
and to weigh the Milky Way

I find this cluster much easier to see than 5053 and it resolves into a graininess with the 15”
but is only a hazy patch with the Mewlon 210, admittedly from not ideal skies. Its appearance i
n my larger telescopes is similar to this Seestar image.

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[Clear Skies]

Amazing, indeed, that this one hasn't made it to OotW before..!

My most recent observation for this globular was less that 2 months ago, the early morning of 2 April in France (session (https://clearskies.eu/astronomy/observing/sessions/sessions2024/2apr2024/) / blog (https://clearskies.eu/blog/astrotrips/2apr24/)). I was primarily targeting the little galaxy MCG+05-33-043 (PGC50187) that is nearby, but of course logged an observation for the cluster, too. 14" SCT @ 168x / 29'.

NGC5466


Grainy, with AV slightly elongated NE to SW with a notable branch on the south side running towards the SW. The cluster is slightly brighter west of the middle. The cluster is "peppered" with brighter stars, mag. 14 and fainter. With AV the cluster is slightly flattened on the north side on a line from ENE to WSW, with that and also due to the branch on the south side the cluster is somewhat comma-shaped.

1/2 FoV to the WNW is the galaxy MCG+05-33-043 (PGC50187).

MCG+05-33-043


An extremely faint, slightly north-south elongated glow, only visible with AV but not stellar. Even in brightness, no detail visible. The galaxy forms the tip of an elongated triangle with the base of two mag. 14 stars on the NE side aligned NE to SE.

PGC1840778 to the north is not visible.

1/2 FoV to the ESE is the globular cluster NGC5466.

As noted in the observation, north of MCG+05-33-043 is even smaller and fainter galaxy PGC1840778, but that one was out of reach.

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Here's the observing guide (https://clearskies.eu/csog/downloads/dsfootw2024/#21).

[lamperti]

With a 10" at 45x: "Very faint, yet broad and almost square in shape."
With a 20" at 192 & 272x: "Almost like an open cluster, possible a Class XII. No concentration towards the center. A scattering of "bright" stars with some milkiness. (Type XII and pictures confirm description.)

[Raul Leon]

Hi, here's my observation from 4/4/2011: Ngc 5466 globular cluster in Bootes : mag: 9.2 ; size:11' ; fairly large but dim ; using averted vision and lots of patience, more stars come into view. I used a 17mm Ethos at 133x with my 14.5 StarStructure f/4.3
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[wvreeven]

With my old 6" Newtonian telescope from southern France in 2008 I saw this globular cluster in my 50 mm finder. At 64x a large, not quite round glow with one side sticking out a bit. At 146x a few stars were resolved.

[Steve Gottlieb]

These are some of my notes through a variety of apertures. The sites and observing conditions also varied significantly.

48": at 375x; highly resolved cluster with chains of brighter stars, particularly in the halo, which extend to at least 8', but also passing through the richer 3' to 4' central section. The surface brightness is relatively low due its loose structure, even in the core. The brighter stars seems superimposed over a layer of much fainter resolved stars. At 697x, there were way too many visible stars for a reasonably accurate count but at least 250 stars resolved.

17.5": large, low surface brightness, 7'-8' in diameter. Ragged appearance with an irregular surface brightness to the core and halo. About 60 stars from mag 14-15.5 resolved at 280x-380x. The brighter core is relatively large, perhaps 4' in diameter and appears offset to the west side of the resolved stars. Numerous faint stars are peppered across the core.

13.1": roughly three dozen stars resolved about 14th magnitude across the entire disc

8": fairly large, low surface brightness with a loose appearance. Some faint stars resolved across the disk at 100x to 165x.

80mm finder: clearly seen at 18x but no resolution

[akarsh]

My only record of this object is through my 25x100 binoculars from Anza Borrego desert California, although I have seen it at least once in 2005 or 2006 with my then 8" f/8 telescope.

"Beautiful! A large, diffuse round glow with a gradually somewhat brighter middle. Can be held continuously with direct vision. A bright orangish (?) star is nearby. Reminiscent of a faint and diffuse comet."