Exploring the Treasures of the Southern Cross
24 Aug 2016
Every time I look up at night, the first thing my eyes are drawn to the familiar pattern created by the Southern Cross. To me it is like some sort of celestial gyroscope – there it is… wheeling around the South Pole… All is well with the universe.
I am not surprised that when Dante and Beatrice emerge from their underworld journey visiting the souls in Hell, Purgatory, and Paradise in Dante Alighieri’s “Divine Comedy” (completed in 1321), that the first thing they see is “four stars, the same / The first men saw, and since, no living eye” – a fabulous reference to the Southern Cross that was last visible at Dante’s latitude in 3000 B.C. (and no one else wrote about it in Europe until after Amerigo Vespucci’s voyage in 1501).
The smallest constellation, Crux lies at the eastern end of a dazzling sea of radiance – a spectacularly rich region of the Milky Way – and it is full of celestial wonders and jewels. and what better place to start than the Jewel Box itself?
NGC 4755 (The Jewel Box) – Open Cluster
RA 12 53 38 Dec -60 21 00 Mag 4.2 Size 10′
In John Herschel’s immortal words, “… this cluster, which though neither a large or rich one, is yet an extremely brilliant and beautiful object when viewed through an instrument of sufficient aperture to show distinctly very different colours of its constituent stars, which give it the effect of a superb piece of fancy jewellery.”
I reckon this must be one of the most famous quotes about any southern deep-sky object (although strangely it’s also probably one of the most misquoted quotes, too, popping up in all sorts of off beam variations.).
It’s a superb sight at low magnification, red and blue stars intermingled with yellows and whites in a profusion of sparkling light. Three brilliant jewels form a triangle; a dazzling bluish white diamond at the apex, two gorgeous pale yellowish topazes forming the base, one of which (the Yale Kappa) in the south eastern corner resembles a piece of jewellery itself – a lovely topaz set in a pendant of tiny diamond chips.
The Jewel Box’s three most dazzling jewels lie framed within the triangle … the westward star of the three is a sapphire, a beautiful bluish star embedded in an arc-shaped sparkle of unresolved starlight like diamond dust.
The middle star, and the smallest of the three, is a brilliant white diamond.
And then there is the third star, the one Herschel described thus: “… centred is this glittering nest of stars, like a ruby set in a set of diamonds and sapphires, is a red giant comparable to Betelgeuse.” It forms a startling contrast to all the other stars, and to my eyes it has the most subtle hint of golden; truly a gorgeous gem among gorgeous gems.
When you can drag your eyes away from this glorious trio, there are all the other jewels lying scattered carelessly in this celestial jewel box. Over there, to the southwest of the triangle… the brightest stars form two delicate semicircles of stars, like two little diamond clips facing opposite directions. Immediately south of these two diamond clips is a long graceful chain of fainter stars oriented northwest to southeast, that look like a delicate chain of gleaming seed pearls. And everywhere else, tiny sparkling stars are scattered around the Jewel Box like an unstrung necklace of mixed gems carelessly dropped into the Jewel Box.
Herschel, and other observers since, report seeing greenish tinted stars in the Jewel Box. Not me. To my eyes the Jewel Box is filled with diamonds of every size, sapphires, topazes, pearls, all scattered on a sprinkling of diamond dust. Just gorgeous!
DY Crucis (Ruby Crucis) – Carbon Star
RA 12 47 24.6 Dec -59 41 41 Mag 8.9
This is a genuine jewel… a ruby star! Mag 1.3 Mimosa (Beta Crucis) is a dazzling diamond on a backdrop of black satin… and there within its glow is one of the loveliest sights in the sky – a rich deep red incandescent ruby. It’s carbon star DY Crucis, but goes by the lovely nickname Ruby Crucis. It’s one of the most beautiful carbon stars out there, smouldering away like a tiny red ember beside dazzling Mimosa. Very striking indeed.
I adore carbon stars. Another beautiful pairing with a carbon star was back towards the end of 2014 sometime (I don’t have my 2014 log book with me so not sure when) when R Leporis (Hind’s Crimson Star) and Comet Lovejoy were in the same field. It was a special treat to see Lovejoy with its bright little nucleus and gossamer smudge of a stubby little tail flying past a small blood red carbon star… I ask you, how much better can it get?
Coal Sack – Dark Nebula
RA 12 53 00 Dec -63 00 00 Size 7°x 5°
Steve O’Meara calls the Coal Sack the ‘Shadow of the Cross’ because in photos the size and shape of the Coal Sack mimics that of the interior of the Cross (and it does, perfectly). The inimitable Admiral William Smyth referred to it as “the Black Magellanic Cloud”. I’ve always wondered about that…
… As the Coal Sack and the Large Magellanic Cloud are roughly the same angular size, it has always looked to me as if the Large Magellanic Cloud was brutally torn out of the fabric of the Milky Way and thrown over there, leaving behind a gaping hole of nothing. Was this how Smyth saw it?
I’ve always loved dark nebulae; exploring those beautiful dark chasms of gas and dust is very beguiling. At first blush they seem like pools of nothingness, then you discover how many variations of darkness the eye can discern: pools of utter darkness, rivers of gentler darkness, wisps of subtle darkness, scraps of undulating darkness, little blobs of nebula as impenetrable as ink. And the Coal Sack has to be one of the best to explore when it comes to variations in darkness.
Naked eye, it is a grand sight in these utterly dark skies – a veritable hole in the fabric of the Milky Way. The 15x70s reveal amazing rib-like structure among the blackness. It’s almost as if one is seeing the skeleton of the Coal Sack, the blacker blackness of the ribs holding the vast cloud of dust and gas together.
One thing the Coal Sack does that other dark nebulae don’t seem to do, is change in a ghostly fashion with averted vision. The ribs round out, become more wave-like, and if I run my eye around the Coal Sack I get the impression of a vast undulating nebula, like a photo of a sea at midnight with slow rolling waves heaving across it. And the foreground stars scattered hither and thither across it add to the impression, looking like sparks of phosphorescence against the black water.
And there, embedded in this vast black ocean, close to Acrux… a gorgeous charred orange star (BZ Crucis), set against the blackness of the Coal Sack like the last dying ember in a campfire… and also the faint glow of –
NGC 4609 – Open Cluster
RA 12 42 20 Dec -62 59 36 Mag 6.9 Size 6′
This is an extraordinary object. Not only because of its stunning neighbourhood, embedded in the Coal Sack with gorgeous orange variable mag 5.2 BZ Crucis between it and the tiny glow of open cluster Hogg 15. And not only because in the 15x70s it seems to flare off BZ Crucis like the silvery spray tail of a comet. But because it actually lies behind the Coal Sack yet its young stars pack enough punch to be visible through this dense dark interstellar cloud. Cool stuff!! It’s a gorgeous little cluster in the telescope…. it shows about 20 stars loosely grouped in a rectangular sort of shape. (BZ Crucis is a foreground star.)
It’s a stunning cluster to visit after the Jewel Box. The Jewel Box is a bunch of dazzlers. This is a smaller bunch of dazzlers… all tarnished and dulled by the Coal Sack smog.
Being in the vicinity, it was but a small hop via BZ Crucis to –
Hogg 15 – Open Cluster
RA 12 43 36 Dec -63 06 06 Mag 10.3 Size 2′
This is also a lovely cluster owing to its neighbourhood. The cluster shows three stars forming a narrow but eye-catching triangular asterism with a fainter extra star thrown in. The triangle is set against a faint glow of unresolved starlight. This is one of those open clusters that remind you that not every open cluster has to be blazingly beautiful to be beautiful.
NGC 4052 – Open Cluster
RA 12 02 01 Dec -63 14 00 Mag 8.8 Size 10′
Another lovely cluster! Beautiful location, positioned 8’ north west of 4.5 mag Theta-1 Crucis and 16′ west of 4.7 mag Theta-2 Crucis. At low magnification it is a large, rich cluster of 10th to 13th mag stars with others glittering in and out of view in the background haze of starlight. At medium magnification it appears much looser, and beautiful chains of stars criss-cross the cluster forming a lovely almost geometric pattern. I think what I love most about open clusters is how different they all are, and each one has something unique to delight the eye.
NGC 4103 – Open Cluster
RA 12 06 40 Dec -61 15 00 Mag 7.4 Size 6′
The cluster lies in a beautiful star field. (That’s the problem with this incredibly dark sky… the star fields are incredibly rich; I spend half my time getting side tracked and wandering around them, dumbfounded at the sheer number of stars that fill my eyepiece.) The cluster is bright and spread out, a group of about 20 stars of equal brightness, standing out beautifully against a grainy haze of starlight. A long string of mag 9 stars make an asterism that looks like Zorro′s Z slashed into the night sky.
NGC 4349 – Open Cluster
RA 12 24 07 Dec -61 52 12 Mag 7.4 Size 4′
Lying just short of midway between Acrux and ε Crucis, NGC 4349 is an exceptional cluster. It displays a swarm of stars that spiral away from a slightly more crowded centre. One of the spirals snakes out in faint stars from the cluster’s western side and curves northwards like a string of tiny diamond lying on black velvet. A pretty mag 8 star is noticeable towards the southeast corner of the cluster.
Hogg 23 – Open Cluster
RA 12 28 37 Dec -60 54 35 Mag 9.5 Size 7’
Hogg 23 appears as a pretty grouping of 6 stars with a yellowish 7.1 mag star in the centre of the cluster. It looks like a little topaz surrounded by tiny ice chips of light. A particularly lovely star field.
Harvard 5 – Open Cluster
RA 12 27 16 Dec -60 46 44 Mag 7.1 Size 5′
Harvard 5 is the third brightest cluster in Crux at 7.1 mag. It is a pretty little cluster with its stars gathered together in a compact diameter of only 5 arc minutes. There are at least half a dozen bright stars glitter among a dusting of fainter stars and starlight.
Hogg 14 – Open Cluster
RA 12 28 39 Dec -59 48 00 Mag 9.5 Size 3′
At medium magnification, the cluster shows only a few stars standing out against the rich background star field. The heart of the cluster is a 10 mag star with some fainter stars gathered around it in a vague arc. NGC 4439, another small cluster, lies roughly south of Hogg 14 –
NGC 4439 – Open Cluster
RA 12 28 27 Dec -60 06 12 Mag 8.4 Size 4′
A beautiful little cluster of stars in a lovely dainty little arc with three faint stars nestled within the arc. A pretty white mag 7 star lies to the NW. it’s a lovely area, such a rich star field.
NGC 4184 – Open Cluster
RA 12 13 38 Dec -62 42 20 Mag – Size 2′
The cluster appeared as a faint grainy haze; no stars resolved, just the odd twinkle that twinkled out before it fully registered on the eye. The surrounding field wasn’t that rich so the hazy-grained cluster stood out more than it would have against a rich star field. I love these little hazy open clusters; like with the cores of globular clusters, I almost go cross-eyes trying to resolve stars and patterns in the hazy glow.
NGC 4337 – Open Cluster
RA 12 24 04 Dec -58 07 24 Mag 8.9 Size 3.5′
This cluster appears as a dainty, grainy haze standing out well against the background field. A delicate chain of mag 11 and 12 stars cut through it a very pretty fashion.
Ruprecht 98 – Open Cluster
RA 11 58 48 Dec -64 34 00 Mag 7.9 Size 15′
A pretty cluster! The data give a diameter of 15′ but I can only make out just over half that with between 40 and 50 stars scattered around loosely. A nice mix of moderately bright and faint stars. A faint string of four bright stars with four fainter companions curves gracefully across the northern side of the cluster.
Ruprecht 105 – Open Cluster
RA 12 34 00 Dec -61 32 00 Mag – Size 12′
The cluster is centred on a 7.1 mag star but it was pretty near impossible to distinguish cluster members from the background field. Nonetheless, a lovely view of pretty stars.
Ruprecht 165 – Open Cluster
RA 12 28 36 Dec -56 26 00 Mag – Size 20′
It was tough to separate the cluster’s stars from the background stars, but I could make out a very loose smattering of stars around a 6 mag yellowish star, but with no way of telling where if they were cluster memebrs or where the cluster ended.
Ruprecht 97 – Open Cluster
RA 11 57 23 Dec -62 42 18 Mag 9.1 Size 5′
This cluster appeared as a grainy haze of stars in a circular 5′ area. It looked as if there was a slight concentration of stars in the northern portion of the haze. A few stars glittered in and out of view… resolved for an instant before disappearing back into the haze.
Trumpler 20 – Open Cluster
RA 12 39 32 Dec -60 38 00 Mag 10.1 Size 7′
A beautiful star field with a brighter patch that looked like seed pearls stitched onto lace. But it was impossible to distinguish the boundaries of the cluster among all the stars But worth the search, a lovely view while I rummaged around looking for edges.
Loden 694 – Open Cluster
RA 12 53 31s -60 50 00 Mag – Size 16′
Some faint stars but nothing that stood out against the star field. As it’s 16′ in diameter, was expecting to see more… something at least, but not. So logged as a not.
Loden 682 – Open Cluster
RA 12 47 19 Dec -60 38 00 Mag – Size 28′
The data record the cluster as large – 28′ – but even so, it was difficult to tell it from the background stars. I saw a faint little unresolved roundish fuzz at the location, but that was it.
Loden 565 – Open Cluster
RA 12 08 24 Dec -60 51 00 Mag – Size 11′
These Loden clusters were a dead loss, With this one, I picked up the orange 6.2 mag star that lies in the vicinity of the cluster, but it was impossible to define a cluster at all. Just lots of stars with nothing to distinguish a cluster member from the rest of the crowd. Pretty field, though, so a nice view while searching.
ESO 131-13 – Open Cluster
RA 12 22 49 Dec -59 38 00 Mag – Size 11′
Another rich field with lots of stars! The cluster (or should I say a part of it) appeared as a richer patch within the richness. But there was no way of distinguishing the cluster members from the rest of the crowd, apart from a nice roughly 9 mag star which was a soft lemony colour.
Then it was time for some nice doubles:
Alpha Crucis (Acrux) – Triple Star
RA 12 26 35.8 Dec -63 05 56
Naked eye, Acrux is a beauty, a gorgeous distinct cold blue steel colour. And it is a superb triple in the telescope. The main pair are both brilliant bluish white stars separated by 4″. Alpha-1 is mag 1.3 and Alpha-2 is mag 1.6 and they sparkle beside each other like a pair of diamonds. The 4.8 mag third star lies 90″ away and it appears very slightly yellowish, like a somewhat lower-grade diamond beside the two dazzlers. The sight of this triple always thrills me… even though I must have viewed it hundreds of times.
Iota Crucis – Double Star
A lovely pair with a bright, mag 4.7 yellow primary and a 9.5 mag white star separated by 27″ at PA 22°.
Mu Crucis – Double Star
RA 12 54 35.6 Dec −57 10 40
This is simply one of the most beautiful doubles in the sky. The 4 and 5 mag pair, separated by 35′, are both dazzling blue-white in colour. They lie in a beautiful starry field.
h 4843 – Double Star
RA 12 43 28.3 Dec -58 54 09
A yellow-orange mag 6.4 primary with a tiny grey-white mag 9.8 companion separated by 36.5″ and at PA 95°. Lovely starry field.
Dun 117 – Triple Star
RA 12 04 46.9 Dec -61 59 48
Two almost equal white stars (mags 7.4 and 7.8); the B star with a very faint blueish tint, separated by 22.7″, at PA 149°. The 10.0 mag C star, is a fainter, very slightly orangey colour, separated by 25.1″ and at PA 18°.
h 4548 – Double Star
RA 12 46 22.7 Dec-56 29 19
The primary is a bright mag 5.0 yellowish-white star with a small dim mag 8.9 slightly bluish companion, separated by 51.7″, at PA 166°.
h 4524 – Double Star
RA 12 28 06.7 Dec -60 02 18
An unequal pair lying on the edge of open cluster NGC 4439. Both white, the primary mag 9.4, its companion mag 10.0 separated by 31.1″, the smaller companion at PA 338°. Nice field with the open cluster!
And that was pretty much it for the Southern Cross.
Or not quite… I brought out my Southern Cross Clock and checked the time. I mean really, what other clock could one possibly use on a Southern Cross excursion?
What a grand constellation Crux is! It not only points out the South Pole, it also tells the time remarkably well. I made myself this Southern Cross clock some time back for a couple of kids, but tarted it up and brought it along so that I could have an appropriate timepiece for the Kalahari, where time seems to move very differently to time elsewhere.
I tried to take a photo of it telling the time with my red torch illuminating it but buggered things up because the flash went off… it was blinding on the laminated white clock… and there went my dark adapted eyes.
But hey, I’d finished my cruise around the Southern Cross, so it was time to ward off the freezing desert night temperature with for a mug of hot cocoa for me and a bowl of warm milk for Waldo, my faithful little stargazing companion.
Copyright © Susan Young 2016.