Sand and Stars

A Bevy of Galaxies in Pavo

Victorian Frederic Leighton’s painting of a peacock

23 Aug 2021

When the Dutch navigators Pieter Dirkszoon Keyser and Frederick de Houtman celebrated with stars the exotic animals that they encountered in faraway southern lands, they had no idea how apt the peacock with its spectacular tail filled with beautiful eyespots would be for us observers sitting at our telescopes… for Pavo is filled with galaxies floating in space like the eyespots in the peacock’s magnificent plumage.

Quite apart from being beautiful, the peacock’s spectacular feathers are an extraordinary evolutionary trait that fittingly, for a constellation, involves light… the feathers’ bright colours are produced not by pigments, but rather by tiny, intricate two-dimensional crystal-like structures. Slight alterations in the spacing of these microscopic structures cause different wavelengths of light to be filtered and reflected, creating the feathers’ many different iridescent hues.

Not surprisingly, the brilliant teal eyespots (also known as ocelli) have long fascinated scientists. Charles Darwin found them to be especially striking, and he wrote: “As no ornaments are more beautiful than the ocelli on the feather of various birds… they deserve to be especially noticed.”

Pavo’s galaxies, too, deserve to be especially noticed. But because they are in the faint-to-extremely-faint and fuzzy category, they are all too often overlooked – other than the impressive face‐on spiral NGC 6744. (And even then, one can get lead astray by the published magnitude of 8.3. Since this galaxy is very large, 13′x20′, the light is spread over a large area, producing a surface brightness of just 14.1.)

The peacock’s tail feather with their beautiful teal eyespots

However, as a galaxy groupie, so to speak, observing galaxies is not only about what I am seeing in the eyepiece (a faint glow of silky grey light with, if I am lucky, the delicate swirl of a spiral arm, or smaller structure like bright knots, dark rifts or mottling) but also about what I am seeing in the eyepiece (faint light from a vast aggregate of gas, dust, and billions of stars and their solar systems, that has travelled millions of light years in an expanding universe). Knowing that incredibly ancient light has ended its inconceivable journey by being processed by my eyes, my brain and my mind, involves me directly in the great immensity and evolution of the universe… which pretty much pushes my brain and imagination to their limits.

Indeed, I think that observing galaxies, more than any other objects, pushes one to discover new limits. Sure, taking a journey to some far distant island universe pushes your eyes and equipment to their limits. But it pushes other limits, too, those of curiosity and comprehension. Patience and perseverance. And beauty… galaxies push the limits of commonly accepted conventions of beauty when you find immeasurable beauty in the diversity of small, pale grey smudges of light floating in the great void of space.

Thus it was with Pavo’s galaxies; an evening of pushing limits.

As a semantics aside, the collective noun for a family of peacocks is a bevy… and last night at the eyepiece, I couldn’t think of a better collective noun for all the galaxies in Pavo.


16″ f/5 Dobs; 150x, 228x, and 333x 

Image credit ESA/Hubble
NGC 6744. Image credit ESA/Hubble

NGC 6744  Galaxy

RA 19 09 46.4   Dec -63 51 28   Mag 8.5   Size 20.1’x12.9’   SB 14.4

This massive face-on barred spiral galaxy could almost be a picture postcard of our own Milky Way taken and sent by an extragalactic friend. It gives me the tantalising sense of how a distant observer might see our galactic home, and I have to confess that my observation of this galaxy wasn’t entirely objective! 

I really strove to get a sense of our own galaxy’s striking spiral arms wrapping around a dense, elongated nucleus and a dusty disk; imagining how our spiral arms would lie… and I even  imagined where our solar system would be.

But unfortunately, with NGC 6744’s low surface brightness, it wasn’t possible to see any structure at all.

It shows as a faint, large oval, elongated north-south, with a large bright core, but no sign of a nucleus. A few faint foreground stars are superimposed on the face of the galaxy.

The galaxy even has a distorted companion galaxy – NGC 6744A – that lies 12’ NW of NGC 6744. You can see it in the lower right hand side of the image. But despite a diligent search, I couldn’t see this tiny companion galaxy. 

ACO S805 Galaxy Cluster

This was a superb observing experience – it is always thrilling to look at members of a massive galaxy cluster, never mind one that itself is a member of a super-cluster – in this case the gargantuan Pavo-Indus super-cluster of galaxies that includes more than a dozen other similar galaxy clusters. (The Pavo-Indus super-cluster is believed to contain well over a thousand galaxies.)

ACO S805 lies around 220 million light years away… the light reaching my eye set out when the first mammals were evolving from the nearly extinct Therapsids; which pretty much pushed this mammal’s imagination to its absolute limits. 

ACO S805 Galaxy Cluster. DSS image

The Uranometria All Sky plots six cluster members – IC 1464, IC 1465, IC 1466, IC 1467, IC 1469 and ESO 104-7. I spent a tremendous few hours identifying and observing them, as well as five additional galaxies that I could see clustered around with the clustered members. What a view!

IC 4765

RA 18 47 18.1   Dec -63 19 52   Mag 11.4   Size 1.8’ x 1.1’   SB 13.9

I began with IC 4765 at the centre, which is presumed to be the gravitationally dominant cluster member. It is the brightest galaxy in the eyepiece, surrounded by a host of faint companions – a lovely sight!

It appears as a fairly faint oval glow elongated ESE-WNW. It has diffuse edges, and brightens to a small, well-concentrated core, but with no sign of a nucleus.

IC 4766  

RA 18 47 35.7   Dec -63 17 32   Mag 13.4    Size 0.9’x0.3’   SB 12.3

This galaxy shows as a very faint oval glow that brightens to a surprisingly bright, albeit it very small, core.

IC 4767  

RA 18 47 41.6   Dec -63 24 20   Mag 13.4    Size 1.1’ x 0.4’   SB 12.9

This galaxy shows as a very faint, exceedingly thin and diffuse slash of light elongated NNE-SSW, with a tiny brighter core.

IC 4764  

RA 18 47 07.5   Dec -63 29 06   Mag 13.6    Size 0.8’ x 0.3’   SB 12.3

This little galaxy looks remarkably like IC 4767, only it is about a third smaller and elongated NNW-SSE. But it shows the same very faint, exceedingly thin and diffuse slash of light, with an exceedingly tiny, very slightly brighter core.

IC 4769  

RA 18 47 44.0   Dec -63 09 26   Mag 13.1   Size 0.8’x0.4’   SB 13.9

This galaxy shows a faint, oval gossamer glow, elongated NW-SE. It brightens to the centre to a small core.

ESO 104-7  

RA 18 47 18.0   Dec -63 21 35   Mag 12.9    Size 0.8’ x 0.5’   SB 12.2

This galaxy lies roughly 2′ south of IC 4765 with a 10th mag star directly south of it. It is faint, very small, and round. Averted vision showed it to brighten very slightly to the centre.

IC 4770  

RA 18 48 10.3   Dec -63 23 01   Mag 13.2   Size 0.4’ x 0.3’   SB –

This galaxy appears as an extremely faint, extremely small, round  glow. Averted vision showed it to brighten marginally towards the centre.

IC 4771  

RA 18 48 23.8   Dec -63 14 51   Mag 14.5   Size 0.4’ x 0.3’   SB 13.7

This galaxy shows as an extremely faint, tiny round glow. Averted vision shows a very small and very slightly brighter core.

ESO 104-8  

RA 18 47 23.0   Dec -63 18 35   Mag 14.4   Size 0.8’ x 0.4’   S.B –

This galaxy required averted vision to pick up; and it appears as an exceedingly faint, round puff of faintest grey light.

PGC 62391  

RA 18 46 51.6   Dec -63 18 51   Mag –   Size 0.4’x0.3’   SB –

This galaxy shows as an extremely faint, extremely small round glow. Averted vision didn’t reveal any brightening to the centre.

ESO 104-2  

RA 18 46 53.9   Dec -63 21 39   Mag 14.1   Size 1.0’x0.3’   SB –

This little galaxy shows as an extremely faint round glow. With averted vision I could detect no brightening to its centre.5

The Pavo Group of Galaxies

This is a lovely group of galaxies; to the west lies the famed NGC 6872 and its interacting companion, and to its east lie the other six members of the group. It really is a tremendous observing excursion around these galaxies.

The Pavo Group of Galaxies. DSS image

NGC 6872  

RA 20 16 56.4   Dec -70 46 06   Mag 11.8   Size  6.0’ x 1.5’   SB 14.0

IC 4970  

RA 20 16 57.6   Dec -70 44 59   Mag 13.9   Dim 0.7’ x 0.2’   SB 11.6

NGC 6872 is an amazing galaxy! Not only is it one of the most elongated barred spiral galaxies known, it is also the second largest spiral galaxy discovered to date, measuring over 500,000 light-years from tip to tip. (In terms of size it is beaten only by NGC 262, a galaxy that measures a mind-boggling 1.3 million light-years in diameter!) The galaxy’s unusual shape is caused by its interactions with the smaller galaxy, IC 4970. They both lie roughly 300 million light-years away from Earth… when their light left, reptiles were evolving, and about 75 million years into the light’s voyage the first creature to dominate Earth were evolving… the mighty dinosaurs. (Who doesn’t love dinosaurs?)

As the second brightest of the Pavo Group, this galaxy shows as a moderately bright, small oval glow, elongated NE-SW. It brightens to a small core. With averted vision I managed to pick up small curves of the two lengthy spirals. The arm that curves NE was extremely faint and  extremely thin and very short, the merest curve that a curve can do. The arm that flows SW was also extremely faint and extremely thin, but it was a touch longer than the other arm.

IC 4970, lying just north, required averted vision to pick up; and it appears as the smallest, faintest little round daub of dim light.

NGC 6876  

RA 20 18 18.8   Dec -70 51 31   Mag 11.3   Size 2.8’x2.2’   SB 14.0

This galaxy is the brightest member of the Pavo Group, and it appears as a moderately bright, round, glow that brightens to a slightly brighter core.

NGC 6877 

RA 20 18 36.0   Dec -70 51 14   Mag 12.2   Size 1.1’x0.6’   SB 11.8

This galaxy lies a mere 1.5’ east of NGC 6876, and it appears as a very faint, very small oval glow elongated north-south.

NGC 6880  

RA 20 19 30.0   Dec -70 51 35   Mag 12.1   Size 2.0’x0.9’   SB 12.6

This galaxy appears as a faint, small oval glow elongated NNE-SSW, with a very slight brightening to the centre.

IC 4981  

RA 20 19 39.3   Dec -70 50 54   Mag 13.1   Size 0.9’x0.3’   SB 11.5

This galaxy lies just east of NGC 6880’s NNE tip, and it appears as a very faint, and very narrow, and very small, diffuse streak, elongated NW-SE.

IC 4972  

RA 20 17 42.7   Dec -70 54 54   Mag 14.5   Size 1.1’x0.3’   SB 12.7

This is an extremely faint, extremely thin, streak of dim light, elongated NNE-SSW. No sign of a central brightening.

 A lovely interacting triplet

This is a superb trio of interacting galaxies. Albeit faint silky swirls in the telescope, it is always stupefying to see galaxies interacting in a graceful galactic dance choreographed by gravity, The trio lie 190 million light years away. Two of the galaxies – NGC 6770 and 6769 – were listed by Russian astronomer Boris Vorontsov-Velyaminov of Sternberg Astronomical Institute, Moscow University in his 1959 catalogue of interacting galaxies. A majority of the systems were found on the POSS plates from the Palomar 48-inch Schmidt astrograph. (And as an extra treat this lovely triplet of galaxies lies just over one degree southeast of Pavo’s gorgeous dazzler of a globular cluster – NGC 6752.)
Image credit ESO

NGC 6769  

RA 19 1822.7   Dec -60 30 04   Mag 11.8   Dim 2.3’x1.5’   SB 12.9

This is the brightest of the trio, and appears as a faint round glow that brightens to a somewhat brighter core. On the DSS image you can see that it and NGC 6770, that lies just 1.9’ to the east, are clearly interacting. No sign of the interaction in the telescope, but as always, it is extraordinary to know what is going on between the objects you are holding in your eyepiece, even if you can’t see it.

NGC 6770 

RA 19 18 37.3   Dec -60 29 47   Mag 11.9   Dim 2.3’x1.7’   SB 13.3

This galaxy, a mere 1.9’ to the east of NGC 6769, is almost identical to it, being a little smaller and a little fainter. They really look lovely together… their brighter cores remind me of a car with dodgy headlights coming through the mist.

NGC 6771 

RA 19 18 39.5   Dec -60 32 46   Mag 12.5   Size 2.3’x0.5   SB 12.5

This galaxy, lying 3’S of the dodgy headlights, is a lovely faint, slim streak, elongated NW-SE. It brightens to an extended central area. While examining the galaxy with averted vision, I thought that a very faint stellar nucleus popped into view, but alas, only once, so not logged as a stellar nucleus; may well have been wishful thinking.

McLeish’s Object

RA 20 09 28.1   Dec -66 13 00   Mag 15.1   Size 1.0’x0.3’   SB 13.7

McLeish’s Object. DSS2 image

The name “McLeish’s Object” has a wonderful air of mystery to it, and alas, it is still a wonderful mystery… even at the highest magnification I wasn’t able to pick up even a hint of this strange little galaxy (never mind the minute galaxy with which it is interacting – McL B – just off its NW tip). The size of McLeish’s Object and its magnitude just couldn’t beat the glare from yellowy-white mag 3.6 Delta Pavonis, no matter how I tried to shield it from the glare. 

IC 5052 

RA 20 52 06.3   Dec -69 12 14   Mag 11.2   Size 5.9’x0.8′   SB 12.7

DSS image
IC 5052. DSS image

I really like edge-on galaxies… and this is a real little beauty. It is a beautiful, bright narrow NW-SE streak; evenly luminous, with no central concentration. It is very slightly spindle shaped, with a very slight bulge at the centre, and tapering to the tips at both ends. Lovely!

Copyright © Susan Young 2017