A Story about Crux

The Southern Cross is a pattern of five bright stars that are prominent in the southern sky. The four brightest stars are arranged in an approximate cross shape (specifically a “Latin cross”, which has unequal arms).

These stars could be seen from Greece 3,000 years ago. The ancient Greeks included them in a larger pattern representing their mythical centaur, a magical creature with the upper body of a human and the lower body of a horse.

Much later, around the year 1500, Western explorers sailing in the southern oceans noticed the cross-shaped pattern of stars. No doubt because of the symbolic importance of a cross in Christian mythology, they saw it as a distinct grouping, standing out amongst the stars of the centaur.

The stars and a portion of the sky surrounding them were eventually (1928) included in our modern list of 88 constellations as “Crux”, the Latin for Cross. But we just call it the Southern Cross.

Meet the Family

The five brightest stars are, in order of brightness, known as alpha Crucis, beta Crucis, gamma Crucis, delta Crucis, and epsilon Crucis. They are labelled on the accompanying photograph, taken by Dieter Willasch, using lower-case Greek letters.

Photograph by Dieter Willasch.

Alpha Crucis (also called Acrux) lies at the foot of the Cross. To the naked eye it looks like a single star, but even a small telescope will show that it is actually two stars close together. Both stars are young, massive and very energetic – at least 16 thousands times brighter than our Sun.

Incidentally, alpha Crucis was first seen as a double star from South Africa. This discovery observation was made from Cape Town in 1685 by a Jesuit priest, Father Jean de Fontenay. De Fontenay and five other priests were on their way to the East, and stopped off at the Cape en route. Their ship anchored in Table Bay on 1685 May 31. They stayed for several nights in a comfortable pavilion in the garden of the Fort and even gave a star show to Simon van der Stel, the Commander of the Dutch Cape Colony. The group set off on June 17.

Beta Crucis (also known as Becrux and Mimosa) is the brightest star along the short arm of the cross. Like Acrux, it is young, massive and also a multiple star system. It is about twice as luminous as Acrux!

Gamma Crucis (also called Gacrux) lies on the long arm of the Cross, opposite Acrux. It has an orangish colour, visible to the naked eye and obvious through binoculars. Unlike Acrux and Mimosa, Gacrux is older and is classified as a red giant type of star. If it was a person, it would be happily retired.

Delta Crucis (also called Imai) is classified as a subgiant star and is on its way to becoming a red giant.

These four stars (and many others in this region of the sky) were born out of the same primordial cloud of gas. They are thus stellar siblings, and much like young humans, have left the nest and are beginning to set off on their own adventures in space, and time. Astronomers call these groups of familial stars “associations”. The stars of Crux belong to the Scorpius–Centaurus Association and lie about 400 light-years (four thousand million million km!!) away from us.

Epsilon Crucis (also called Ginan), the odd-one-out in the cross pattern, is an old (about 2 billion years) giant star and, like Gacrux, also has an orangish hue. However, because it is quite faint, its pretty colour isn’t obvious to the naked eye. But through binoculars or a telescope, it’s colourful nature really shines.

Photograph by Dieter Willasch.

From any point on Earth at about the latitude of Cape Town and further south, the Southern Cross is always above the horizon at any time of the night throughout the year. The further north you go, the less visible Crux becomes. From Johannesburg, for example, Acrux dips below the horizon at certain times. From Egypt, India, and southern Texas (USA) only Gacrux can be seen, barely skimming the southern horizon.

Crux is best seen from early February until mid-June. Mid-April it is at its highest point in the sky at midnight; late in May it culminates at 21:00 and towards the end of February it culminates at 03:00.

The region of the sky in which Crux lies, is stunningly beautiful. We see Crux embedded within the Milky Way, a broad band of ghostly light and dark splotches.

In some cultures this glowing band of soft light was thought to be the severed tail of a mighty celestial dragon. To the ancient Greeks it was divine milk, squeezed from the breast of Hera, the queen of the gods.
The Kalanga people of Zimbabwe saw it as a pathway followed by elephants and hunters, while the Venda people traditionally describe it as a path along which the ancestor spirits walk.

The /Xam-ka !’e people (usually written as /Xam) said that it is a glowing pathway, created by a girl of the ancient race (who came before the Bushmen), meant to show the way home for travellers at night. She scooped up the ash and embers from a camp fire and cast them into the sky, where some of the glowing coals made the red stars we can see.

Meet the neighbours

As mentioned above, the stars of Crux were originally a part of Centaurus. The photo below, taken by Christine Kersting, shows the centaur rising, the Milky Way running vertically up the centre of the frame, and a cloudy patch near upper right. Below-centre lies Crux.

Photograph by Christine Kersting.

Photos such as these are very pretty, but the large number of stars make it tricky to identify the constellations. The camera captures many, many more stars than you can see with the naked eye, because most of the stars are too faint to trigger the chemical receptors in your eye.

You’ve probably heard someone comment that when you get out in the countryside where it is dark, and free from the horrid, terrible, wasteful artificial light that some people insist on shining up into the sky at night (why?!?), they could see “millions of stars” in the sky. This is nonsense. Or perhaps the bedazzled individual isn’t good at counting. It’s true that there are billions and billions of stars in the sky, but you can’t see them with the naked eye.

With a small telescope, you can see about 1.6 million stars, if you closely examine every little piece of the sky. A pair of binoculars will reveal 600,000 stars. The most sharp-eyed humans who are skilled observers, can, under the best conditions, see about 13,000 stars. Average Joe and Nominal Betty, under the best conditions, can see about 4,300 stars. If you’re in the suburbs, outside a city, and you scan the whole sky, you’re down to only about 800 stars. If you’re in the city, the night sky will usually have a greyish or orangish colour, and objects on the ground are clearly visible, bathed in the sickly glow of light pollution. Under these conditions, it will be quite a challenge to see 400 stars in the entire sky! From the centre of Cape Town, for example, at a push you can count around 150.

Just think about that. From the centre of Cape Town, you can see 150 stars. If you simply switched off all the lights that are shining into the sky (?!?) you could see 4,300 stars. Four thousand three hundred, versus 150. Also think for a moment, what this unwanted light at night is doing. For one, it is a pure waste of money, because generating light requires energy and resources, and energy is money. I’m sure you all know the famous equation: E = mc2, which relates energy (E) to money (m) and two cents (c2). Well, ok, that’s perhaps not completely true. But you get my point: wasted light is wasted money.

There is no good reason to shine light upwards. OK, if you’re operating a searchlight and it is wartime and you’re looking for an enemy aeroplane that’s about to bomb you into next Tuesday unless you can see it and shoot it down first, yes, that’s a good reason to shine light up into the heavens. But that’s about it.

Turning night time into an insipid version of the day is not only recklessly wasteful of precious resources, but it doesn’t do any favours to plants, animals, insects, and us humans. Life on our beautiful planet Earth evolved for millennia under the influence of a natural rhythm of dark and light, night and day. The complex chemical flux within the cells of a living organism are influenced by light levels. Some reactions are triggered, others inhibited, by bright light. Changes in the equilibrium of a dynamic system can be accommodated, but only up to a point. Our biochemistry is tied to the coming and going of the Sun. It would be foolish to pretend otherwise.

If you’re still reading, thank you, and please accept my apologies for the meander. The point was, in Christine’s lovely photo, we are overwhelmed by the many stars. I counted – there are 5,494 stars in her photo. To make the constellations and asterisms recognizable, I’ve played cosmic connect the dots and identified a few features.

Crux is now obvious, just below of centre, the long arm pointing to the right. Above, below and to its left is the sprawling Centaurus, 9th largest of the constellations. The centaur is rising backwards, or upside-down, depending on how you think. The beast’s head is partially obscured by that tree at bottom-left. His back legs are high up in the sky, and his front legs are low down towards the horizon. The centaur’s front hooves are marked by two particularly prominent stars, labelled “Pointers”. The two Pointer stars point to Crux. The brighter of the two Pointers (lowest down) is known as alpha Centauri; the other Pointer is beta Centauri.

Alpha Centauri is a true celebrity because it is the nearest star system to the Sun. Now, the Sun is a star, so the Sun is the nearest star to Earth, making alpha Cen the second-nearest star system to the Earth. But wait, there’s more. Alpha Centauri isn’t just a star – it is a star system. What we see as one star with the naked eye, a telescope reveals as being two stars.

Speaking of telescopes, everyone knows the telescope was invented by an Italian college dropout named Galileo Galilei in 1609. Now, that isn’t true. Galileo didn’t invent the telescope. He heard about this wonderful new gadget, figured out how the trick was done, and made his own. Only his was better. And he was soon using it to discover a slew of things in the heavens. Presumably the bona fide Dutch inventors were using their telescopes to observe the mooie dames in the tulip fields, or they would have become famous, too.

Using his telescope, Galileo discovered a double star in Orion, in 1617. His team-mate, Antonio “Fat Tony” Castelli, discovered three double stars between 1617 and 1627. Between then and 1680, three more double stars were discovered (in Aries, Gemini, and Cancer). These observers were all stuck in the northern hemisphere, and couldn’t see the beautiful southern skies. The first telescopic observer of alpha Cen was the famous Edmund Halley. As a young bloke he went to the remote island St Helena in 1677 and carried out a series of observations. He took a look at alpha Cen, but didn’t notice anything special. Then in 1685, a French priest, Jean Richaud, stationed in the southern part of the Indian Peninsula, became the first person to turn a telescope on alpha Cen and see it as a double star. This makes alpha Cen the 9th double star to be discovered with a telescope.

Being such a bright object, alpha Cen is of quite some interest to astronomers. To see why, let’s take a quick side trek to the diaphanous land of all-else-being-equal, where enthusiastic hand-waving hides a multitude of sins. Very roughly speaking, then, we can say that all stars generate the same amount of energy; they’re just big balls of exploding hydrogen. In other words, are stars are intrinsically equally bright. Also, we can say that stars are scattered about the cosmos willy-nilly, so that they end up lying at different distances from Earth; some very close, some very far away. Yet, if you go outside and look, you see bright stars, faint ones, and everything in-between. This must mean that the brighter stars are closer to us. I did say, roughly speaking.

It’s always worth paying close attention to things close to you. What you’re going to have for lunch this afternoon is probably more relevant than what you’re going to have for lunch next August. That noise in the underbrush, the snapping twig, and the sudden rising of the hairs on your neck, should probably be investigated right now, and less attention paid to the distant call of a lone mallard. Or to continue the avian foraging theme, a bird in the hand is a low-hanging fruit. Roughly speaking.

Measuring the distance to a star is a remarkably difficult thing to do. It’s like looking for a needle in a hay stack when you’re blindfolded and your only source of light is a blue Moon. It’s complicated.

As mentioned earlier, the telescope was first used for serious astronomy in the early 1600s. In the coming centuries, astronomers were looking all over the sky at lots of different things. Yet by the time the telescope was two hundred years old, no one had been able to answer that ancient question: how far away are the stars? The race was on, and astronomers knew that whomever could measure the distance to a star first, would be famous, maybe even crowned Emperor of the Universe. But, for two centuries, and counting, not a sausage. That’s how complicated measuring stellar distances is.

A part of why this was so perplexing is that astronomers knew that nearby stars should change their position in the sky. Specifically, if you wait half a year between your observations, they should change positions quite dramatically.

This change in position is called parallax. Here’s an easy demonstration. With both your eyes open, point at something far away. Then close first one eye, then the other. (If you close both eyes at the same time, you’re really not helping.) As you’re looking, first only with the left, then only with the right eye, your finger will appear to change position. It’s not really changing it’s position, but it just looks like it is. That’s parallax.

Now imagine your nose is the Sun. Weird, I know. Then, pretend your left eye is the Earth in January, and your right eye is the Earth six months later. And pretend your finger is a nearby star, and the thing you pointed at is a star far away. That’s what astronomers were doing. They would carefully measure the positions of bright stars, and then compare measurements taken six months apart, when the Earth had swung to the other side of the solar system along it’s orbit around the Sun. And they found nothing. No change.

The main reason there was no change, is that it was really, really small, and their telescopes weren’t good enough. By “really, really small” I mean: take a R2 coin, now throw it about 5 km from you. Do you notice how big it looks? Can you see it? Well, the old astronomers couldn’t either. The diameter of the coin, when seen from several kilometres away, is the size of the change they were trying to measure.

But then, going into the roaring 1800s, things improved and instrument makers were getting craftier. In 1820, when the Brits decided to establish a permanent observatory at the most-distant part of the African continent, they designed and built state-of-art equipment. And so it came to pass that, in 1831, a pernickety Scot, whom his parents called Thomas Henderson, found himself sitting atop a snake-infested hillock in a swamp outside Cape Town, studying the stars.

Henderson wasn’t down on his luck. In fact, he’d just been appointed His Majesty’s Astronomer in charge of the Royal Observatory in Cape Town. How’s that for street cred?! OK so the fancy huge new building of His Majesty’s Royal Observatory didn’t have proper toilets, but it did have fabulous classical Doric pillars at the front door. OK so the pillars were fake [go to the SAAO and tap them gently, you’ll see what I mean] but the astronomical equipment was cutting-edge. Henderson and his henchman, William Meadows, made good use of the equipment.

He’d received a tip-off that alpha Centauri, a star well known to him (since he often checked the instruments by drawing a bead on the star) seemed to be moving a lot. A handsome young astronomer, Manuel Johnson, sequestered on the island of St Helena, had noticed that the position of alpha Cen had changed a lot from the olden days, i.e. about 1752. These earlier, good-quality observations were made by Nicolas-Louis de Lacaille, a French deacon with a dog (“does yor dûg bite?”) who spent a few years in Cape Town observing the southern skies. Professor Ian Glass wrote a whole book about him, which you should read.

Anyway, Johnson told Henderson about alpha Centauri, and Henderson began measuring it fastidiously. Meanwhile, his wife was composing snarky poems about the horrible observatory they’d been banished to, calling it a “dismal swamp”. Image if she had Instagram! Henderson resigned after about a year, leaving Cape Town in 1833, presumably in a huff. Before leaving, however, he had collected a wealth of data, making good use of the equipment. This allowed him to measure the distance to alpha Centauri. And this was Big News! Only, it wasn’t.

Henderson didn’t publish his results. Perhaps he thought his findings were too good to be true. Perhaps the aliens told him to keep the secret. Whatever the reason, in 1838 the German wunderkind Herr Doktor Professor Friedrich Wilhelm Bessel announced that he was the first human ever to measure the distance to a star. His target was a star in Cygnus the Swan which had been dubbed “The Flying Star” (quite fittingly; it’s located just ahead of the Swan’s right wing.) Bessel proudly shared his work and took the cake. Not only was he the first to measure stellar distance, but his star was really close to us: just 98 thousand billion kilometres. Or 10.4 light years in techspeak.

When Henderson finally published his observations, about 7 years after he made them, he could show that alpha Centauri was even closer, a mere 41 million million km (or 4.4 light years) away. And it made him the second person to measure the distance to a star. But nobody likes people who come second. Or who write snarky poems.

For almost a century, alpha Centauri held pole position as the nearest known star. This record was broken by yet another Scot observing in South Africa: Bob Innes. Innes (who went by Robert Thorburn Ayton Innes) was an ex-wine salesman and very popular with the ladies. He was also a brilliant astronomer, and in 1915, observing from Johannesburg, he discovered Proxima Centauri, a dim little star that, to this day, is the nearest known star to the Sun. Ian Glass wrote a book about that, too. You should read it.

As you’ve just seen, bright = near is only roughly-speaking true. Proxima Centauri is too faint to be seen in binoculars. Another famous nearby star, Barnard’s Star in Ophiuchus, a mere 6 light years away, is a dim red dwarf, nicknamed “Dopey”. OK that last bit isn’t true. But it should be.

In the diagram above, the yellow circle above the label “Pointers”, shows the location of Proxima Centauri.

This diagram also highlights a few other things. Notice at the top of the image, the “False Cross”. It’s called the False Cross because it isn’t the real cross. In-between the two lies the Diamond Cross; the origin of this name is unknown. The Milky Way just to the left of the Diamond Cross contains one of the most beautiful objects in the sky, a vast region of bright stars, gas, and dust, known as the eta Carinae Nebula. Looking again at the Diamond Cross, you’ll notice the long axis points to a fuzzy blob labelled “LMC”.

The LMC looks a bit like a piece of the Milky Way has been torn off and tossed aside, perhaps out of that dark patch between the Diamond Cross and Crux. In a sense, this isn’t infinitely far from the truth. The LMC – Large Magellanic Cloud – is a nearby galaxy which has quite possibly been distorted by the gravity of our own Galaxy. This tidal disruption also happened to the Small Magellanic Cloud (just out of shot to the right of this image). These two Clouds are known as the Cape Clouds (“Kaapse Wolkies” in Afrikaans).

The two Clouds feature in the traditional astronomy of many southern African peoples. In the semi-desert Nyae Nyae region of Namibia the !Kung people saw the LMC as a patch of the soft thornless greyish-coloured grass which they gather and use as a bed.

The /Xam-ka !’e people, who originally occupied a large part of western South Africa, and spoke /Xam [the extinct language in which South Africa’s national motto is written], saw the two Clouds as a male and female steenbok.

The Karanga of Zimbabwe called the LMC “Maguta”, meaning plenty, and the SMC was “Mazhara”, meaning famine. They believed that when the SMC appeared more clearly than the LMC, a drought would ensue.
There are few more features marked on the image that are of interest.
The green stick figures/lines in the diagram are Frowned Upon by Serious Astronomers, because the green lines aren’t official. What is official are the red lines. These indicate the formal boundaries of the constellations. I’ve indicated the patch of sky that is officially assigned to Crux and Centaurus.

Another feature indicated in the image is a blue circle marked SCP. SCP is an abbreviation for Secure Copy Protocol, which is a method of securely transferring files between two networked devices. It’s also short for south celestial pole. That’s the point around which the stars seem to rotate. Christine took this photo from Cape Town, which is at a latitude of about 34° South. This means that the SCP is also (and always) 34° above the horizon. In other words, the number of degrees you are away from the equator is the same as the altitude of the pole.

In the final diagram, let’s see how – and why – to find the SCP. Notice that blue line – it drops from the SCP straight down to the horizon. Voila! You’ve just found True South. So if you ever get lost, then hunker down and settle in and wait for nightfall. Then use the method I will explain in the next paragraph to locate south. Voila! You’re no longer lost!

There are several ways of using the stars as a navigation aid. Traditional Sotho and Tswana lore explains how to find direction at night: if you want to travel west, then keep the Southern Cross on your left and the Pleiades (Seven Sisters) on your right.

Using only Crux, you can find south. As per the diagram, shown in purple, extend the long arm of the Cross four-and-a-half times in the direction it points. That’s the south celestial pole. Roughly. Then just go directly down to the horizon, and you’re on your way home.

But beware! Look up and notice the False Cross. If you mistake it for Crux, and extend its long axis (cyan line), you’ll find yourself wandering about in the desert for 40 days and 40 nights, never to be seen again.

And this segue neatly brings us back to the subject of this essay: heraldry.

The Southern Cross has found its way into the heraldic consciousness of a number of southern nations.

In Australia, Crux appears on several state flags and badges, including the national flag, which accurately depicts all five stars. The national flag of New Zealand also shows Crux, as four red stars, edged with white. In an attempt to reflect their differing apparent magnitudes, alpha is shown as slightly larger and delta as slightly smaller than the other two stars. The unofficial flag of Christmas Island accurately depicts Crux, while the flags of Samoa and Papua New Guinea show a somewhat distorted Southern Cross. Both the national flag and the arms of the Federal Republic of Brazil include Crux.

Crux also appears on the coins of a number of countries (for some reason, coins of the northern hemisphere tend not to depict constellations). Brazilian, Australian and Western Samoan coins depict Crux (including epsilon Crucis) accurately. Several New Zealand coins show the Southern Cross rather crudely as four stars in a symmetrical pattern.

Oddly, Crux has made no impact on Southern African heraldry, which employs more earthbound symbols. Nevertheless, it does feature in the star-lore of the region.

The /Xam saw the two Pointers as male lions; they were once men, but a magical girl turned them into stars. The three brightest stars of the Southern Cross they saw to be female lions. To the Khoikhoi, the Pointers were known as Mura, “The Eyes”, of some great celestial beast.
Other San groups knew the stars of Crux as “the giraffes”, because “these stars are big, like giraffes”. The !Kung called the Pointers and Crux, “Giraffe Eyes”. The Pointers are male giraffes. The four stars of the Cross are female – alpha and beta Crucis are mother giraffes; delta and gamma Crucis are their daughters.

In Sotho and Tswana tradition, alpha and beta Crucis, together with the Pointers, made up Dithutlwa, the four giraffes. The Venda know them as Thuda while the fainter stars of the Cross were Thudana, “the little giraffes”. The Tswana see the brighter pair (the Pointers) as male giraffes, while the Sotho make them females. Sotho lore also says that when the giraffe stars are seen close to the south-western horizon just after sunset, they indicate the beginning of cultivating season.

Cue Brünnhilde

To wrap up: Crux is the smallest, brightest constellation in the entire sky, functions as a stellar guide to find direction at night, and is widely celebrated in the symbolism and lore of southern hemisphere peoples.

Protecting South Africa’s astronomical heritage