Object Of The Week April 26, 2020 – Abell 3526

Abell 3526, ACO 3526, ACG 3526, Centaurus Cluster

Cluster of Galaxies

Constellation: Centaurus

RA: 12 48 51.8
DEC: -41 18 21

Dimensions: About 6 degrees across

Our galaxy, the Milky Way, is part of a group of galaxies called the Local Group. The Local Group is part of the Virgo Supercluster, at the center of which lies the Virgo Cluster. The closest neighbor of the Virgo Supercluster is the Hydra-Centaurus Supercluster, which is formed of several galaxy clusters. And one of those clusters is Abell 3526.

Wikipedia says: "The Centaurus Cluster (A3526) is a cluster of hundreds of galaxies, located approximately 170 million light years away in the Centaurus constellation. The brightest member galaxy is the elliptical galaxy NGC 4696 (~11m). The Centaurus cluster shares its supercluster, the Hydra-Centaurus Supercluster, with IC4329 Cluster and Hydra Cluster.

The cluster consists of two different sub-groups of galaxies with different velocities. Cen 30 is the main subgroup containing NGC 4696. Cen 45 which is centered on NGC 4709, is moving at 1500 km/s relative to Cen 30, and is believed to be merging with the main cluster."

As it goes with clusters of galaxies, it usually is not entirely clear which galaxies are members and which are not. Some galaxies may be foreground or, more likely in case of a close by cluster like this one, background objects. And it sometimes is unclear where the cluster ends and where non-cluster space begins. The A23 map in Uranometria 2000.0, for instance, has a circle that does not contain NGCs 4601, 4606, 4603B, 4603C, 4751, 4811 and 4812 but it does contain NGC 4603D, to name just one. Also, Alvin Huey's Abell Galaxy Clusters downloadable observing guide doesn't seem to include those galaxies. However, it does contain a great set of finder charts for the galaxies in the cluster starting at page 284.

In July 2019, after the solar eclipse in Chile, I visited an amateur observatory and managed to observe these galaxies in and near Abell 3526 using a 12" dob telescope:

NGC 4603A: At 160x a faint glow.
NGC 4603C: At 160x a faint glow.
NGC 4601: At 160x a faint glow.
NGC 4603B: At 160x a faint glow.
NGC 4603: At 160x a large faint glow.
NGC 4616: At 160x an exceedingly faint glow next to a star.
NGC 4603D: At 160x a faint glow.
NGC 4622A: At 160x a faint glow.
NGC 4650A: At 160x a faint glow barely visible.
NGC 4650B: At 160x a faint oval glow.
NGC 4650: At 160x a large oval glow.
NGC 4645A: At 160x a faint glow right above a reasonably bright star.
NGC 4645B: At 160x a faint oval glow next to a faint star that us net ti a very bright star.
NGC 4645: At 160x a faint, large oval glow.
NGC 4672: At 160x a faint long glow next to three stars.
NGC 4696D: At 160x a very faint glow.
NGC 4696A: At 160x a very faint glow.
NGC 4677: At 160x a faint glow.
NGC 4683: At 160x a faint glow.
NGC 4696B: At 160x a faint glow between several faint stars.
NGC 4696E: At 160x very faint.
NGC 4709: At 160x a round glow.
NGC 4706: At 160x a faint, thin glow.
NGC 4696: At 160x a large oval glow with a brighter oval center.
NGC 4744: At 160x a faint, oval glow.
NGC 4743: At 160x a faint, thin glow.
NGC 4730: At 160x a faint glow.
NGC 4729: At 160x a faint, round glow.


As always,

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

Great observation, Wouter. I only have a record of 4696, from this time of the year in 2012 (Central Australia, pristine sky, D = 150 mm, F/12, ocular 6.5-19.5 mm): "NGC 4696. Galaxy at center of the Centaurus cluster. Slight elongation toward the faint star may be spurious."

Hi All,

This cluster of galaxy has, according to me, the double interest to be observed: it is one of the brightest AGC, and there is a jewel in it: NGC 4650A.
Here are my related observations:

Attachment 3854

Attachment 3855

Attachment 3856

Attachment 3857

Here are my reports, if you want to know how these galaxies can be viewed in a 20" Obsession in Namibian sky:
http://www.deepsky-drawings.com/agc-3526/dsdlang/fr

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

Thanks for that addition Bertrand!

Checking my notes, I've logged 62 members of the Centaurus Cluster. The first observation was in April 1989 from northern California and the most recent in April 2019 in Coonabarabran.

Last April I also had a good view of the polar "wings" of NGC 4650A through a 25" at 244x. For me, when I stared at the galaxy directly the wings vanished, but would pop into view as soon as I used averted vision. So, I could make them "blink"!

NGC 4650A was discovered by Argentine astronomer J.L. Sérsic in 1967 on the southern extension of the POSS (see 1967ZA.....67..306S). But the original discovery was made 82 years earlier (19 Mar 1885) by Pietro Baracchi, the observer on the 48-inch (speculum) Great Melbourne Telescope. He found it, as you'd assume, while observing NGC 4650, but didn't notice the polar ring. In addition he discovered and sketched 5 other galaxies in the cluster with NGC letter designations (NGC 4603A, 4603B, 4603C, 4696C, 4696E) as well as several ESO members.

All of these galaxies (and several more he discovered) would have regular NGC designations except for one important issue -- his discoveries were never published!

Thanks for the additional info, Steve. How did you learn of Baracchi's observations?

Quote:

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Originally Posted by wvreeven

Thanks for the additional info, Steve. How did you learn of Baracchi's observations?

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See https://astronomy-mall.com/Adventure...By%20GMT-2.htm

I may adapt this for an article in Sky & Telescope. I just finished a similar one on the unknown discoveries of E.E. Barnard (won't be published in the magazine until late next year)

Thanks! Great read :)

Huge galaxy crowd in which I only picked up some "specials" from.

sketch NGC 4650A, 24", 400x, NELM 7m0+
Attachment 3858

sketch NGC 4672, 28", 312x, NELM 7m0+
Attachment 3859

As is often the case, Steve, you supply an overwhelming amount of data that has totally clogged up my own to-do list! However, tis is a GOOD problem, so thanks!

I've just finished the processing of my 2016 drawing of NGC 4650A. We took a look at some of the others as well but I tend to forget what I don't draw very quickly. There are certainly many interesting galaxies in the area.
16", 225x, Namibia:
Attachment 3869Attachment 3870