Circinus and Geometry
28 Apr 2017
In his book, The Assayer (1623), Galileo famously wrote: “Philosophy [natural science] is written in this grand book — I mean the universe — which stands continually open to our gaze, but it cannot be understood unless one first learns to comprehend the language in which it is written. It is written in the language of mathematics, and its characters are triangles, circles, and other geometric figures, without which it is humanly impossible to understand a single word of it; without these, one is wandering about in a dark labyrinth.”
The French astronomer, Nicolas Louis de Lacaille couldn’t possibly have picked a more appropriate scientific instrument to place in the southern skies than that incredibly important tool of geometry – a compass.
Squeezed in between Centaurus’ forefeet and the splendidly geometric Triangulum Australe, it is the constellation that symbolises the greatest language of all… the language of our universe.
(Interestingly, before the 18th century, when one leg was modified to take a pen or pencil, compasses had two sharp points, like dividers. The user scratched the writing surface in the shape of a circle and then inked the scratches.)
If there is one item I wish I had from my schooldays it is my first geometry set.From day one at school, I liked maths. When the little tin with its ten mathematical instruments introduced me to geometry I fell in love with maths; the language of the universe. Most people probably last held a compass or divider in school; faithful Luddite that I am, I use both frequently. In the absence of Giotto’s famous O-drawing talent… its my trusty compass all the way for circles and my divider gets a lot of use because I adore maps and am always measuring distances on them, plus on occasion they are very useful when my star hopping to some dim and difficult object goes awry, and they are also useful for accuracy when I am sketching.
Last night I spent the most wonderful time exploring Circinus. Albeit small, it is an elegant naked eye constellation; one of the few constellations that looks like what it is. It holds a few lovely DSO delights, and a host of extremely dim and difficult objects!
Observations
16″ f/5 Dobs at magnifications of 150x, 228x and 333x
Alpha Circini – Double Star
RA 14 42 30.0 Dec -65 48 00 Mag 3.2 Sep 15.7″ PA 232°
I started off with the constellation’s lucida – the compass’ hinge – not only is it a fascinating star in its own right, being the brightest rapidly oscillating Ap star in the night sky, but it is, to me, one of the prettiest double stars. The primary is a bright ever-so-slightly off-white star; its companion is a much smaller and fainter reddish star. It is beautifully set off by a small arc of fairly bright stars lying just 10′ to the southeast.
E97-13 – Circinus Galaxy
RA 13 14 09.9 Dec -65 20 18 Mag 10.6 Size 6.9′x 3.0′ SB 13.8
The galaxy is surprisingly bright for a galaxy that went unnoticed until 1977. Indeed it is surprisingly bright for a galaxy lying within the bright glow of the Milky Way with all the intervening stars and whatever other gas and dust lies along our line-of-sight to it. It appears as a small, bright, even core surrounded by a very small, faint and flimsy glow that looks like a somewhat disorganised oval. It lies in a very pretty neighbourhood… the galaxy lies in a rich field of stars that form some attractive and appropriate geometric asterisms in the near vicinity.
NGC 5315 – Planetary Nebula
RA 13 53 57.2 Dec -66 30 52 Mag 13.0 Size 14″ Mag cent * 14.4
This was a challenging planetary nebula. I had to pick it up by blinking with the UHC filter. Once found, it looks like an out-of-focus star, except for its pale bluish colour. The very small, round, bluish droplet of light lies in a beautiful busy star field, and just 4′ east of a lovely yellowy-white mag 7 star.
Bernes 145 – Dark Nebula
RA 14 48 36.0 Dec -65 15 00
A dark nebula is always a treat, and this one, lying 42′ ESE of Alpha Circini, doesn’t disappoint. It shows as a black oval patch against the rich starry background. The reflection nebula, vdB-Ha 63, lying just northeast of the dark nebula appears as the very faintest haze seen with averted vision – almost like an impression of a haze more than an actual haze; only picked up because I knew where to look for it.
NGC 5823 – Open Cluster
RA 15 05 26.6 Dec -55 37 00 Mag 7.9 Size 12′
This is a lovely, large, bright and rich open cluster. It looks like an arum lily to me with curls and strings of stars curving outwards from a narrow gathering of stars that form the stem. Most of its prominent “lily-petal” stars are 11th to 12th magnitude; the host of fainter stars adding to the lily-like effect because they give the lily’s petals the soft satin sheen peculiar to an arum lily.
Pismis 20 – Open Cluster
RA 15 15 23.1 Dec -59 04 00 Mag 7.8 Size 4.5′
Gorgeous! Small, with a large brightness range, four prominent stars are arranged in a tight little box-shape towards the middle. The cluster’s lucida, a lovely yellow mag 8.2 star, forms the box’s southeastern corner. The rest of the stars spill out from the boxy shape in a couple of rays, the longest of which points to the northwest.
NGC 5288 – Open Cluster
RA 13 48 35.6 Dec -64 41 11 Mag 11.8 Size 3′
A faint but really dainty cluster that stands out beautifully against the rich starry background. The faint stars spread out in an elongated grouping ENE of a very pretty mag 7.8 golden star. It has three interesting strings of faint stars which almost join together on the cluster’s southern edge.
NGC 5715 – Open Cluster
RA 14 43 39.0 Dec -57 34 00 Mag 9.8 Size 7′
This faint but obvious cluster looks just like the little donkey hoof prints that I find in the sand on my walks! Its rough U-shape opens up to the east, and its northeastern region is the most highly concentrated area. The cluster lies in a gorgeously rich field of stars and stands out well.
NGC 5359 – Open Cluster
RA 13 59 45.2 Dec -70 24 00 Mag – Size 8’
This loose collection of stars resembles a long coiled snake comprised of ten stars that run in a roughly north-south direction, with its head to the southwest; its tail to the northeast. The stars vary between 10th and 11th mag and the celestial snake stands out beautifully, not least because the field stars are noticeably sparse around the cluster.
Copyright © Susan Young 2017