A Mountain In A Sea Of Stars
8 Nov 2016
As a South African, one of the most moving sights in the night sky is Mensa – our beautiful and imposing Table Mountain depicted in the stars, its faint stars sharing the sky with ancient gods and heroes, fabulous creatures and the tools of art and science.
Apart from being the only terrestrial feature on our planet to be immortalised as a constellation, the mountain is fabulous in its own right. Fascinating geology, an over-abundance of floral species, a rich history… and most importantly for astronomy, Table Mountain exerted its powerful and charismatic pull on three eminent astronomers: Abbé Nicolas Louis de Lacaille, Sir John Herschel, and Sir Thomas Maclear.
The indigenous Khoisan people of the Cape called the mountain Howrikwaggo – “Mountain in the Sea”. In May 1503 the Castilian-Portuguese navigator, Antonio de Saldanha, anchored in the bay at the foot of the majestic mountain. He named the bay Aguada de Saldanha, or “the watering place of Saldanha”. He also made the first recorded ascent of the mountain, not because it was there, but in a bid to regain his bearings and locate the rest of his fleet. He named the mountain Taboa do Capo, or “Table of the Cape”.
In 1601 a Dutch seafarer and cartographer, Joris Van Spilbergen, mistook a bay further north as Aguada de Saldanha (modern day Saldanha Bay) and, thinking he had made a new discovery, he named the bay with the magnificent mountain Tafel Baai, or “Table Bay” on account of the “high hill, flat and square like a table.” Thus the mountain became known as Tafelberg, or Table Mountain to the Dutch settlers of 1652, who settled at the Cape in order to start a food and fresh water refreshment station for ships headed to the East.
Nicolas Louis de Lacaille
French astronomer Nicolas Louis de Lacaille arrived in Cape Town on April 19, 1751 with his dog Gris-Gris, a stray that he had picked up at the start of his voyage south, to catalogue the southern sky and measure the arc of the meridian near the Cape among a host of other tasks. His observatory, which he set up in the rear courtyard of a private house near the shore of Table Bay, was dominated by the sight of the magnificent mountain.
When Lacaille commemorated Table Mountain by putting it on the first version of his planisphere published in 1756, he gave it the French name Montagne de la Table. The Latin translation, Mons Mensae, appeared on the second edition of 1763. In 1844 John Herschel proposed shortening it to Mensa. Francis Baily adopted this suggestion in his British Association Catalogue of 1845, and it has been known as Mensa ever since.
Table Mountain is famous for its orographic cloud formation that lies over the top of the mountain like a white tablecloth when “the violent south-easter blows”, as Lacaille put it. He gave Mensa the appearance of being capped by a white cloud like its terrestrial namesake by incorporating part of the misty Large Magellanic Cloud into the new constellation.
John Herschel
Ships can see Table Mountain from 150km away (but that hasn’t stopped the Cape Peninsula from laying claim to hundreds of shipwrecks) and on January 15, 1834, John Herschel recorded in his diary, “At dawn this morning James knocked on our cabin door and called out Land! Rose and hurried on Deck whence the whole range of the Mountains of the Cape from Table Bay to the Cape of Good Hope was distinctly seen, as a thin, blue, but clearly defined vapour. The Lions Head was seen as an Island the base being below the horizon. Called up Marg who also came on Deck just before Sunrise. It was a truly magnificent Scene…”
Later in the same entry he records, “…The shore, still nearing, grew bolder & more rugged & broken “The wild Pomp of Mountain Majesty” developed itself & certainly nothing finer than this approach of South Africa can be conceived…”
Thus Sir John Herschel, the remarkable polymath, astronomer, scientist, philosopher and artist, arrived in Cape Town, where he spent the next 4 years.
He selected as his home (and observatory) a Cape Dutch estate called Feldhausen, just six miles from Table Mountain, which he described as one of the most magnificent sites he had ever seen.
Table Mountain lies within the Cape Floral Kingdom, home to an amazing 8,200 plant species. An estimated 2,200 species of plants are found on Table Mountain alone – many of which are endemic to the mountain and can be found nowhere else.
The Herschels were dazzled by the natural floral beauty of the Cape. They produced over one hundred exquisite water colours, John outlining in superlative detail in pencil, and Margaret brushing in the exquisite colours.
Thomas Maclear
Yet another astronomer has a connection to this mountain. Thomas Maclear arrived at the Cape on January 7, 1834, taking up the post of His Majesty’s Astronomer at the Cape. (After long service he retired in 1870 and settled in Mowbray, Cape Town, where he died on 14 July 1879.) During the first four years of his work at the Royal Observatory Maclear enjoyed the friendship and collaboration of Herschel.
One of Maclear’s most important tasks was to re-measure and extend the arc of meridian measured by Lacaille some 80 years earlier. Lacaille’s measurements in the mid-18th century had concluded the meridian to be 1,000 feet longer in the southern hemisphere than the north. In essence, he showed the Earth was slightly pear-shaped. The British Admiralty, however, wanted this enigma solved and from 1837 to 1847 Maclear and his assistants spent a large proportion of their time in the field work of this endeavour.
The results proved that Lacaille’s measurements were accurate, but that his latitudes had been affected by the gravitational attraction of mountains, particularly at the northern point of his arc. The results also confirmed that there is no significant difference between the shape of the earth’s southern and northern hemispheres.
Some of Maclear’s beacons are still used by cartographers, such as the Maclear Beacon at the highest point on Table Mountain.
Chandra X-Ray Observatory’s first light
Quasar PKS 0637-752 in Mensa was the Chandra X-Ray Observatory’s first light on August 15, 1999. And what a first light, gathering all that ancient light from about 6 billion light years away! The X-ray jet, observed for the first time, is a dramatic example of a cosmic jet. It has blasted outward from the quasar into intergalactic space for a distance of at least 200,000 light years. The mind boggles.
Observations
10″ f/5 Dobs; magnifications of 90x, 144x and 208x
In the Kalahari, I am about 875 odd kilometres from Table Mountain as the crow flies, but last night as I scrambled up and down its celestial slopes on a wonderful astronomical trip, I took a lovely memory trip too… recalling the times I’ve hiked up Table Mountain and with whom… labouring up the precipitous Platteklip Gorge path which Antonio de Saldanha took, or ambling up the mountain’s other gentler side which John Herschel recorded in his diaries, or standing at the top beside Maclear’s Beacon, blurring my imagination to cut out the skyscrapers as I look down toward Lacaille’s former residence, 7 Strand Street.
NGC 2122 Emission Nebula & Open Cluster
RA 05 48 48.0 Dec -70 04 00 Mag – Size 4.5′
The nebula appears as a beautiful, fairly bright glow of nebulosity with a few roughly 12 mag stars scattered across it. The stars have a very pretty and unusual appearance – as if they were covered in the faint haziness, like looking at them through a swathe of very transparent gauzy haze. The nebula responded beautifully to the UHC filter.
NGC 2103 Emission Nebula
RA 05 41 42.0 Dec -71 19 59.3 Mag – Size –
An irregular glow of hazy nebulosity that really responded nicely to the UHC filter. A few very faint stars appear to be embedded in the glow. The edges seem to simply fade into the surrounding sky in a very appealing fashion.
NGC 1711 Open Cluster
RA 04 50 37.4 Dec -69 59 02 Mag 10 Size 2.4′
A beauty! A rich cluster which looks remarkably like a globular cluster, containing an intensely bright core which appears very mottled, just like a globular’s core when it is on the cusp of being resolved. The core is surrounded by a well resolved halo. A pretty little string of tiny stars twist away to the southwest.
NGC 1520 Open Cluster
RA 05 37 51.1 Dec -76 48 20 Mag – Size 5′
Despite appearing as a sparse open cluster of about 11 stars in a loose gathering, it stands out well against its background star field. A pretty knot of five stars lies in the south of the cluster, containing a beautiful roughly 9 mag white star.
NGC 2019 Globular Cluster
RA 05 31 56.7 Dec -70 09 35 Mag 10.9 Size 1.0′
I observed this when I was looking at the LMC globular clusters a few days ago, but took another squizz because it’s lying in the Mensa’s misty tablecloth. It appears as a small, faint, round glow of soft starlight with a brightish core. No resolution.
NGC 1754 Globular Cluster
RA 04 54 18.4 Dec -70 26 31 Mag 12.0 Size 1.6′
Lying in Mensa’s cloudy tablecloth, this is another of the LMC’s ancient globular clusters. It forms a delightful “double” with a roughly 11 mag star that lies about 30″ to the southeast, albeit the large “primary” looking decidedly out of focus! The globular shows as a faint, small, round droplet of hazy starlight. It lies in a lovely haze of stars.
NGC 1841 Globular Cluster
RA 04 45 24.2 Dec -83 59 53 Mag 14.1 Size 2.4′
This Large Magellanic Cloud ancient globular cluster is situated an astounding 14.5° south of the centre of the LMC, close to the border with the southernmost constellation Octans. In fact, NGC 1841 is not too far from the south polar star Sigma (σ) Octantis (roughly 6.5°), making it the southernmost globular in the sky. Lying in a star-sparse region of the sky, it appears as a fairly large, round, faint glow, with a very weak concentration. No resolution.
And to end a gorgeous double star –
Innes 277 Double Star
RA 05 53.5 Dec -71 08 Sep 3.9″ PA 190°
Beautiful! A beautiful orangey star embedded in the mistiness of the Large Magellanic Cloud with a very close, faint ashy companion. It reminded me of being on top of Table Mountain when the clouds roll over… a small beacon in all that misty haziness.
Copyright © Susan Young 2016