Astronomy Beginners Guide: Ancient Constellations

by Duncan Lunan

The patterns imposed on the stars by man – the constellation figures – are now standardised in use by astronomers all over the world.  There’s nothing inevitable about these patterns:  they look very different in different latitudes, and in ancient China for instance the sky was divided up in quite a different way.  Still nearer the equator the tendency is not to form figures at all but ‘ropes’ of stars running in parallel lines across the sky from east to west.  Such ‘star-ropes’ were used by the Polynesian cultures to achieve their amazing feats of navigation between islands widely separated in the Pacific.

It’s interesting that in ancient Sumerian cosmology, the model of the universe was apparently an equatorial one – a half-cylinder running north to south, unkindly compared to a Nissen Hut by the late Arthur Koestler in “The Sleepwalkers”.  In Mesopotamia, the Sumerians were far enough north to see the stars as wheeling around the celestial pole, and indeed the constellation Draco – in which the pole was located at the time – features in cylinder seals with the Plough and the Lion as early as 4000 BC.  The implication is that some of them, at least, must have lived much nearer the Equator at a still earlier date.

The other implication is that the constellations we place around the pole, at least, were devised in Sumeria and that guess fits the known pattern of Indo-European migration into the Mediterranean and across Europe.  What we now call the classical constellations came to us from ancient Greece, with a considerable input from the Arabs who were the foremost astronomers meantime.  But although the Greeks devised the stellar classifications which we still use today, there’s much evidence that their star-lore came largely from Egypt – but not entirely, because the polar constellations follow the Mesopotamian pattern  (Lion, Plough, Dragon), not the Egyptian one which included a crocodile and a hippopotamus.  Lions and Bears might well be more prominent in the mythology of a people whose domain reached up into the mountains.  Henri Frankfort, who compiled a great reference work on cylinder seals in the 1930s, thought these figures couldn’t be constellations because Draco, the Dragon, is so faint.  He didn’t realise that in those days Draco housed the pole and the sky turned around it!  The constellation Draco extends far across the northern sky, enclosing the north pole of the Ecliptic on the boundary of Boötes, and the north celestial pole has also been within it for most of the last six thousand years.  

So who designed the most ‘important’ constellations, the twelve houses of the Zodiac within which the Sun, Moon and planets move?   A clue can be obtained by looking for the time when those figures were ‘upright’ with respect to the equator – about 2700 BC, according to the late Prof. Michael Ovenden.   The next question is, where did this happen?

Precession of the Equinoxes

In dating stellar phenomena there’s one very important aid, though it has to be used with some caution.   Due to the pulls of the Sun and Moon on the Earth’s equatorial bulge, the Earth’s axis describes a very slow circle in the sky, known as the Precession of the Equinoxes.  Different sources give slightly different values for the period of Precession, but in round figures it’s 26,000 years.  As a result, when the Pyramids were built the Pole Star was not Polaris but Thuban, the brightest star in Draco.  Polaris, which passes closest to the pole in 2012, early next century, has been regarded as ‘fixed’ in the sky for most of the last thousand years – Shakespeare has Julius Caesar compare himself to it for constancy – though Columbus realised it had to be making a small circle in the sky relative to the new-fangled magnetic compass “…for the needle moveth not” !

13,000 year ago, when Britain was under the ice sheets, the Pole was on the other side of the precessional circle, near Vega in the constellation Lyra.   Vega was in the news when this column began, because the IRAS satellite had discovered a disc of planetary-type material orbiting around the star.  Vega is the brilliant blue-white star which is overhead in the evenings during the summer;  it makes its way along the northern horizon during the winter months and  coming up in the east during the spring.  Vega is circumpolar seen from Britain, which is to say that (in the present epoch) it never goes below the horizon;  so the distance from Polaris to the northern horizon (which is equal to the latitude of the observer) also happens to be the diameter of the precessional circle, seen from here.

Mintaka, the right-hand star in Orion’s Belt, lies almost exactly on the Celestial Equator, which is the plane of the Earth’s equator projected on to the sky.   But Mintaka wasn’t always a marker for the Celestial Equator.  If you stood at the north pole, obviously the Celestial Equator would coincide with your horizon.  At present Polaris would be directly overhead and Mintaka just on the horizon, neither rising nor setting  (though in practise you might still be able to see it, due to atmospheric refraction).  But 13,000 years, ago if you stood at the pole  (with some difficulty, since the Arctic was then open water), due to the Precession of the Equinoxes Vega would then be overhead, near the Celestial Pole.  Since at present Vega comes overhead in Britain during the summer, when Orion is not visible, so too in 11,000 BC at the north pole Mintaka and the other stars of Orion would have been far below the horizon – and therefore far south of the Celestial Equator.  As the Pole moves due to Precession, the Equator moves with it.

Over nearly 6000 years, Precession has had a marked effect on the positions on the horizon where stars rise and set, even (in the south) on which stars are visible.  The classical constellations avoid a circular zone which includes the south celestial pole, but off-centre: it centres roughly on where the pole was when the sky was mapped out.  That evidence suggests that the mapping was done on roughly the latitude of the Mediterranean.  The late Prof. Archie Roy of Glasgow University suggests that the site may have been Santorini (formerly Thera), the volcanic island which is known to have sustained an advanced culture before the devastating eruption, much worse than Krakatoa’s, about 1450 BC.  Thera’s explosion may well have been the inspiration for the Atlantis legend, and both the ancient Greeks and the Trojans may have been descended from refugees.

But Precession only gives us the rough latitude of the map-makers.  Since it takes in northern Mesopotamia;  since events in the Zodiac aren’t affected in the same way by Precession – and since the ancient Lion and probably the Bull are Mesopotamian, my money is on the Sumerians as the mysterious compilers of the maps.  Since I first wrote that, I’ve come across a fascinating book by a Victorian astronomer called Emmeline Plunkett, who worked out a convincing case for the use of the classical constellations in Sumeria well before 6000 BC.  It’s been suggested that they may be depicted in the carvings of the oldest known stone structure, Göbekli Tepe in Turkey  (10,000 BC), and even in the paintings of Lascaux and other sites in France, dated to around 30,000 BC.   

Whether or not the classical constellations were derived on Thera (Santorini), as Archie Roy believes, it is certain that the explosion of Thera around 1450 BC caused a major cultural shake-up in the Mediterranean.   It was a worse disaster than Krakatoa, in its initial violence and its consequences, since the tidal waves were penned within the waters of the ‘Med’.   It’s believed that survivors from the island civilisations may have founded the cities in Greece and Asia Minor which were to fall out a few centuries later in the Trojan War.

The ruins at Thera Stan Zurek, CC BY-SA 3.0 , via Wikimedia Commons

But ancient Egypt, primarily an inland civilisation, escaped largely unscathed, and Archie Roy believed that the Greeks’ knowledge of the constellations came from there – despite the fact that the Egyptians had a different mapping of the sky around the Pole, featuring a crocodile, a hippopotamus and the leg of an ox, instead of the Bears, the Plough, and Boötes, the Herdsman.   That’s the best evidence – despite the other constellations which were the same – that the Egyptians didn’t devise the star maps which we use today.   Archie came to accept that in his later years, acknowledging in a lecture on his 80th birthday that an origin in Sumeria was more likely.  Now it seems possible that the figures are older still.

It’s interesting then the emperor Ch’in, who united China  (named after him), built the Great Wall, and was buried with his army of terra-cotta figures, ordered a great burning of the books because he claimed to have rediscovered the ancient knowledge and found later texts to be corrupt.  Surviving texts date the origin of the world to 2350 B.C.  (contemporary with the second phase of work at Stonehenge)  and the origin of astronomy to 2500 BC (contemporary with completion of the Great Pyramid).  It’s even more interesting that Ch’in himself was buried in a great pyramid, of earth, which has still to be opened.  An American missionary named Geil, who walked the Great Wall in the early 1900s collecting legends of its origin, found that the stories told nearest the centre of the empire – perhaps the most reliable – held that the Wall was built as an image of something in the sky.  Geil considered the idea that the Wall and the dragons of Chinese art both represent Draco, but   (like Henri Frankfort)  he believed this couldn’t be true because Draco is too faint.  He too failed to realise that between 2850 and 2500 BC the pole star was Thuban, the brightest star in Draco.  Geil himself suggested that the Wall represents the Milky Way, which certainly is prominent in Chinese star-lore – but not in a way which makes ancient know ledge differ from the new.  The long, twisted figure of Draco the Dragon is found in many other places, however.  Although all its stars are faint, it contains the pole of the Ecliptic  (the Sun’s path in the sky)  and for much of human history it has also contained the celestial pole. 

But there were other cultures who felt the urge to match the shapes seen in the sky with great figures on the ground.  For instance, some at least of the figures ‘drawn’ on the plain of Nazca in Peru, and also found on the local pottery of the time, can be matched up with the stars.  The sky-legends of Peru are closely linked with those of Mexico, where the Maya and later the Aztecs worshipped Quetzalcoatl, whose planet was Venus but whose symbol was the winged, feathered serpent.  The high point of the Maya civilization was 200 BC  (contemporary with the building of the Great Wall)  to 200 AD, but the oldest Maya sites go back to 2600 BC, contemporary with the Pyramid builders.  The oldest civilization in Peru was a coastal culture which raised great platforms, astronomically aligned, around 2700 BC – contemporary with the building of Silbury Hill and the great stone circle of Avebury, with its great serpentine Avenues, in England – when the Pole Star was Thuban in Draco.

Avebury Wikityke at the English-language Wikipedia, CC BY-SA 2.5 , via Wikimedia Commons

However Avebury was the last of the great stone circles to be built in Britain, apart from the final phase at Stonehenge.  The great astronomical cultures of the ancient world – northwest Europe, Egypt, Mesopotamia, China, Central America and Peru – seem to have been most interested in the sky in the period between 3000 and 2500 BC.  One or two astronomers, such as Victor Clube and Bill Napier, have suggested that there may have been a reason for this, perhaps a spectacular display of comets.  So far, however, no written astronomical records have been found for that time, and the evidence is circumstantial.

The first astronomical monuments in the UK were great tombs built in Ireland, surrounded by standing stones and oriented towards midwinter sunrise, when the Sun reaches its furthest south in the sky and is ‘reborn’ for the following year.  In a farming culture, the associations with death and rebirth are not hard to follow.   But around 3000 BO, first in Ireland and then in the Shetland Isles, the great stone circles became independent of the burial grounds and came to be used as observatories.  Many smaller circles and standing stone arrays were constructed, with astronomical alignments; the last great structures – Stonehenge 1, Avebury, Silbury Hill, Stonehenge II and Stonehenge III – are all from 2900 – 1800 BC, when the celestial pole lay in Draco.  In China, Mesopotamia, Central America and almost certainly North America, long dragons featured in the lore of the sky.   In the British Isles we find flying dragons prominent in Wales.  But in Scotland near megalithic sites there are often carvings  (usually on natural boulders) of ‘cup-and-ring marks’ which might be star maps, and of elaborate spirals, interconnected and counter-rotating.

Kilmartin heritage event

In equatorial cultures, the stars are often depicted not in constellations but in ‘ropes’ running across the sky.  The artist Gavin Roberts suggested to me that to the megalith builders, Draco’s shape might have suggested a double spiral of rope coiling down from the pole.  If so, then the counter-rotating spirals would represent the stars south of the celestial equator, and that would support the possibility that the megalith builders knew that the world is round.

The Greek achievement was to organise the mapping.  They charted the stars’ positions precisely and they classified them, within each constellation.  The Romans, who subdued Greece by force of arms, couldn’t improve on that.  Neither could the Moslem scholars who inherited the Greek catalogues, after the Roman Empire and its descendants had fallen on both sides of the Mediterranean.  What commemorates the Moslem achievement, in keeping observational astronomy alive while Europe was in the Dark Ages, is that most of the individually named stars are named in Arabic.  Alnitak, Alnilam, Mintaka, Elnath, Alphecca, Alkaid… all of them Arabic names, though some were corrupted when the great star catalogues began to make their way into Europe.

The stars were first ranked in order of brightness by Bayer in 1603, using Greek letters, from Alpha to Omega.  Flamsteed, the first Astronomer Royal, assigned numbers to fainter stars and his catalogue was published in 1725.  When that happened, the language of scholarship in Europe was still Latin, and that was the language into which the constellation names were translated.  That’s why, if we say that the brightest star in the Eagle is Altair  (Alpha Aquilae), we’re using Arabic, Greek and Latin, recapitulating the scientific history of the last 3000 years.

There are some star names in Latin – Regulus in Leo is one – but mostly these are relatively modern.   Cor Caroli  (‘Charles’s Heart)  in Canes Venatici was alleged to have shone particularly brightly on the night of Charles the Second’s accession, while Pulcherrima  (‘the most beautiful’)  was conferred upon Epsilon Boötis by Otto Struve in the 19th century.

(Cor Caroli is one of the few political appointments in the sky to have stuck.  Galileo tried to name the moons of Jupiter after his patrons, the Medici, and Herschel wanted to name Uranus after George the Third, but nobody else did.  Legend has it that the constellation Coma Berenices – Berenice’s Hair – was devised to pacify a queen’s husband after a dedicated lock of hair was stolen from a temple;  but the influence of patrons is generally limited and the precedent hasn’t been followed.)

There are even a few stars named in English – Barnard’s Star, Innes’ Star, Van Maanen’s – but these are visible only in a telescope, and named after astronomers who discovered they had unusual features.   Many of the fainter stars in the constellations are known simply by numbers – 61 Cygni, the first star to have its distance measured, is a well-known example, since it was once believed to have a giant planet and possibly a planetary system with earthlike worlds.  61 Cygni is a double star, so technically one should refer to 6l Cygni A & B.  Both components are fainter intrinsically than our Sun, but many of the nearest stars are ‘red dwarfs’ which are so faint that no life would probably not be possible on surrounding planets.  They are known only by their designations in modern catalogues: Wolf 359, Lalande 21185, and Ross 154 – are among the stars which are nearer to us than 61 Cygni at 11.2 light-years, yet quite invisible to the naked eye.

On a typical clear night, away from artificial lights, perhaps 3000 stars would be visible to the naked eye, and all of them carry some kind of designation.  But it isn’t necessary to know them all to become familiar with the sky.  There are extremely skilled observers who have memorised the entire star-field visible from their home latitudes, down to the limit of naked-eye visibility and even beyond:  they are dedicated seekers for transient events such as comets and exploding stars, and such names as Alcock  (UK)  and Seki  (Japan)  are attached to many such discoveries – often sharing them, meaning that two or more observers reported the same discovery on the same night.   The rest of us can be content with knowing the constellation figures by sight, the brighter stars in them by name, and the star maps and catalogues for further information as we need it.

Image by Free-Photos on Pixabay

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