Night of the Stars

A CELESTIAL ACADEMY AWARDS

“Pure leagues of stars from garish light withdrawn

Behind celestial lace-work pale as foam, -

I think between the midnight and the dawn

Souls pass through you to their mysterious home.”

~William Hamilton Hayne - Indian Fancy

Step outside on any warm, clear February evening and gaze toward the south. Rising higher as the year progresses, the Milky Way lies well clear of the southern horizon. Easily seen from dark skies and outlying suburbs well away from the hub of the inner city, a treasure trove of celestial 'jewels' awaits the anticipating eye.

Here we can explore the playground of the rich and famous; dazzling open clusters such as IC 2602, the 'Southern Pleiades' and the glorious NGC 3532. Nearby lies the expansive eta Carinae nebula, seeded with the light of many clusters and laced with dark lanes of dust. Multiple and double stellar systems of great beauty abound, a celestial palette of contrasting colours; orange and blue, yellow and red and hues in-between.

Indeed, the observer is spoilt for choice throughout this region. Telescopes deliver an experience that stamps a smile upon the observer greater than the grin of a cat in a cream factory. Constellations like Crux, Carina, Puppis and Centaurus are familiar figures to the initiated, old friends to return to time and time again.

With such a gathering of dazzling 'stars', the mind is tortured with the obvious question, where do I start? Good question and I guess it begs the answer, any damn where before it clouds over!

Best Performance by an open cluster goes to NGC 3532, “Arrows of Outrageous Fortune”:

Around 12° west of Acrux (alpha Crucis) in the “Southern Cross” lies the vast gas and dust cloud of eta Carinae. A 'stroll' through the gaseous environs of this amazing celestial delight reveals many open clusters and double stars. One of the more spectacular clusters lies around 3.3° east and slightly north of eta Carinae’s central region. NGC 3532 literally explodes with stars, a wide field eyepiece struggling to contain all members. Lacaille discovered this showpiece in 1751.

Sir John Herschel was clearly overwhelmed with the beauty of NGC 3532, recording it as:

“A glorious cluster of immense magnitude, being at least 2 fields in extent every way. The stars are 8, 9, 10 and 11 mag, but chiefly 10th magnitude, of which there must be at least 200. It is the most brilliant object of the kind I have ever seen.”

The age is in the region of 200 million years, therefore the stars are more evolved than say the stellar members of the 'Jewel Box'. Many are of spectral type A whilst a number appear yellow and orange, a frenzied dance of celestial fireflies tantalising the observer’s eye.

Observation is indeed an 'art', detail often lost in the immediate razzmatazz of some glorious display. Many a year I delighted and played within NGC 3532’s star-field, oblivious to the possibility of looking beyond the immediate dazzle. In hindsight, I missed a delicate treat. A dark lane divides the stars, tipped with an arrow head of obscuring dust.

Best supporting open cluster goes to IC 2602, “Diamonds Are Forever”:

Just south of the eta Carinae nebula lies IC 2602, the 'Southern Pleiades', discovered by Abbé Lacaille in 1751-1752. Marking the north-eastern point of the 'Diamond Cross', the naked eye can discern a number of stars huddled together around its brightest member, theta Carinae. Needing a wide field to encompass these dazzling diamonds, binoculars are a must here. With an age less than 20 million years, perhaps as young as 4 million, these supergiant blue-white stars are typical of the neighbourhood. Current study points to a distance of 479 light years for this beauty.

A faint open cluster Melotte 101 lies just off the southern edge, composed of around 30 stars of magnitude 8 to 11 with many fainter members visible in large apertures.

Best Young Achiever award goes to NGC 4755, “The A-Team”:

Beta Crucis is the bright star in the 'Southern Cross' nearest 'The Pointers'. Careful observation will show a brilliant diamond with a fainter ruby-like glow within the glare. Attractive in small telescopes, larger apertures show the deep red colour beautifully. Just off beta Centauri, 1½º south-east lies the brilliant 'Jewel Box', NGC 4755. It shelters within its borders around 70 stars including the 6th magnitude family member, orange-red kappa.

Sir John Herschel recorded it as:

“The central star (extremely red) and a most vivid and beautiful duster of from 50 to 100 stars. Among the larger there are one or two evidently greenish [stars.]; south of the red star is one 13th magnitude [Argenlander magnitudes], also red; and near it/s one 12th magnitude, bluish... The same red star taken. Several others laid down, of different shades of green…Though set down by Lacaillé as nebulous, and on that authority entered as a nebula in Bode's Catalogue, no nebula is perceptible in any part of the extent of 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."

To show the colours of these stars that inspired Sir John, a large aperture is needed. Then the observer may see red, orange, white and possibly greenish gems inlaid among a field of faint stars. A small telescope gives a different form to this group. The brighter stars only are seen with the 6 brightest stars forming the shape of a 'figure A', orange-red kappa on the central bar. Most of these suns are of the spectral class B and have a luminosity in the order of thousands of times our Sun. The Jewel Box is thought to lie 7,700 light years distant and is only a few million years old. The star HD 111613 lies 10’ from NGC 4755 and may be a member. If this is so, then this A-type supergiant of magnitude 5.74 has a luminosity of over 80,000x our Sun!

Best Creative Design by an open cluster goes to NGC 3293, “Snow White and the Seven Dwarfs”:

NGC 3293 sits on the north-western reaches of the eta Carinae nebula. Cocooned within a very faint nebulosity obvious in photographs, the colourful members of this stunner contribute to its common name “Diamonds and Ruby Cluster”. One can almost imagine the Seven Dwarfs busily working this celestial mine…

“We dig up diamonds by the score

A thousand rubies, sometimes more

But we don't know what we dig 'em for

We dig dig dig a-dig dig”

Well, not quite a thousand rubies. In fact, only one bright ruby set amongst a brilliant cluster of dazzling diamonds but stunning in contrast. Similar in age to the 'Jewel Box', these young stars lie within a busy region of the Milky Way, the Carina Arm. Lying at a distance of around 8,000 light years, the blue star members are around 6 million years in age, the faint reddish members, lost to smaller apertures around 20 million years. Telescopes show over 50 suns packed into a 10’ diameter, the brightest a red giant of magnitude 6.5.

Many other clusters wait in the wings to be discovered by the curious observer. A telescope aimed this way will tantalise and delight, giving hours of pleasure.

Clear skies and good hunting.

~CosMos