June 2012 night sky guide podcast, transcript and sky chart
To help you learn about the southern night sky, Sydney Observatory provides an audio guide/podcast, transcript of that audio, and a sky map or chart each month. This month’s guide is presented by Geoffrey Wyatt, Sydney Observatory’s Senior Astronomy Educator.
Of course, the astronomical highlight Geoff tells us about for June 2012 takes place on 6 June – the transit of Venus. The following one won’t be until 2117! There is available a ‘Transit of Venus’ book and eBook for the iPad.
Geoff also tells us how to measure and find our way around the night sky. His then guides us on an informative tour of the night sky, with commentary including much, including Sirius the Dog Star, Leo the Lion, ancient civilisations, and Arabic astronomy. He also expresses his gratitude that our constellations were named long ago – so that the pictures they make in the sky are related to mythology or animals which were part of the consciousness of the people who named them. He ponders whether, if we were naming the constellations today, we may call them by more mundane names – like ‘shopping trolley’ or ‘mobile phone’.
Listen to the June 2012 night sky guide audio, or read the transcript below.
SEE THE SKY CHART
We provide an embedded sky map (below) and a June 2012 night sky chart (PDF) which shows the stars, constellations and planets visible in the night sky from anywhere in Australia. To view PDF star charts you will need to download and install Adobe Acrobat Reader if it’s not on your computer already.
BUY THE BOOK
Our annual book, ‘The 2012 Australasian sky guide’, by Dr Nick Lomb has more information and star maps for months from December 2011 until December 2012 inclusive, plus information about the Sun, twilight, the Moon and tides, and a host of other fascinating astronomical information. You can purchase it ($16.95) at Sydney Observatory and Powerhouse Museum shops or other good bookshops, or online through Powerhouse Publishing (additional packing/postage costs apply).
READ THE TRANSCRIPT (after the jump)
Transcript of the June 2012 monthly sky guide audio
Hello, my name is Geoffrey Wyatt. I’m the Senior Astronomy Educator at Sydney Observatory. I’m going to talk to you about what’s visible in the sky for the month of June. The Sky Guide and Audio Guide are available from our website at www.sydneyobservatory.com.au. Also available from iTunes. For more information about the night sky, we recommend that you purchase a copy of ‘The Australasian Sky Guide’ by Dr Nick Lomb.
As we head towards June, the nights are getting cold. You need to have some basic equipment with you before you go outside and enjoy the view. Foremost is a blanket to sit on so you don’t get too wet. Perhaps even a ground sheet underneath that. To keep you warm, you should have something like a glass of Milo or some hot chocolate, and a nice comfy pillow, because there is a lot to be seen and enjoyed at this time of year.
It’s always handy to have with you not only our printed sky map but perhaps a red torch that you can use as well. You need to be able to find your way around the night sky, and there are two measurements that we often need to use.
One of them will always be in a clockwise direction from north. And that is what we describe as azimuth. You need to start off and look north. What we’re going to do now is turn to our right. As we’re looking towards the east, we have an azimuth of 90 degrees. If you turn towards the south, going towards your right again, you’ve now got an azimuth of 180. Turning around another 90 or quarter turn, you’ll be looking due west. And that has an azimuth of 270 degrees. And of course, coming back to our starting position, you can either say we have azimuth of 0 or 360. It doesn’t really matter.
We like to measure positions around the horizon starting at north, going in a clockwise direction as seen from overhead. And then we need to measure an angle up from the horizon, and we call this ‘altitude’. Interestingly, we’ve all got a very nice way of finding altitudes. You see, if you hold your pinkie at arm’s length – it doesn’t matter how big you are, how short you are – for all of us, a pinkie at arm’s length represents about one degree, or twice the size of a full Moon.
A clenched fist at arm’s length represents about 10 degrees, and if you spread hands, so, from your pinkie to your thumb is as big as you can get it. That’s about 20 degrees. So it’s a very convenient way of being able to calibrate your tour of the night sky using our maps.
If you’re using a map from the ‘Australasian Sky Guide’ book or perhaps any one of the number of free programs that you can download that draw up these spectacular images, you’d be very disappointed – I’d have to say somewhat lost if you’re trying to find elaborate drawings in the sky.
Unfortunately, we have simply got a few thousand points or dots in the sky. It’s pretty much impossible to memorise the position of 2,000 to 3,000 points of light, so over the years, people have been playing dot-to-dot and drawing in the imaginary stick figures to help them along the way.
If you use your imagination, you’ll be fine. You’ll be able to draw up some of the constellations or pictures in the sky. Others, I’m afraid: forget it. Give up. It’s not worth it…. they’re impossible. You’ll just have to take our word for it. But armed with imagination and your sky guide, I’m sure you’ll be able to find your way around.
What we’re going to do for the month of June. We’re going to start off shortly after sunset, looking towards the west. Roughly two clenched fists or one hand span above the western horizon, you should be able to see the brightest star in the night sky. It’s not going to appear as bright as it would if it were overhead, because you’re looking through a lot more atmosphere. And it’s going to make it look somewhat dimmer.
You’re looking at a star that’s twice the mass of the Sun, 25 times brighter, but at a distance of 8.6 light years away. It’s simply the brightest star in the night sky. It’s called Sirius, the Dog Star. Hmm, I hear you say. You’ve heard that name before. Yes, of course. It came to Australia as part of the First Fleet. There’s a fairly famous series of novels about a young wizard, and one of the characters in those books is called Sirius Black. He shares his name with the brightest star in the night sky.
The astounding thing is that this star, which is now quite low in the western horizon, was used thousands of years ago by the Egyptians to work out very accurately the length of the year.
What they would do is they would look at it setting in relation to the Sun. For about 70 days, the star Sirius would be lost in the glare of the Sun. And that very first day that Serious popped out, if you like, of that glare and could be seen independently of the Sun is something called Heliacal Rise.
When they were able to see that, they would work out the length of one year to the next, and by year after year after year of observations, they worked out that the average length of the year was 365 1/4 days. Not bad, considering they did this several thousand years ago.
But what is it now? We see a bright star setting in the west and I have to tell you, it’s actually part of a constellation. A constellation is simply a group of stars. An area of the sky. This particular area is supposed to be the large hunting dog, Canis Major. It’s probably too low for us to make out all of the dog at the moment, so we’ll have to wait a little bit longer and come back for that one.
If you found Sirius, what I want you to do is turn towards your right ever so slightly. And not far away there’s another reasonably bright star. In fact it’s the eighth brightest star in the night sky, and it’s called Procyon. Procyon is the brightest star in the constellation of the Small Dog.
Now look, really. We’re a bit late for it, but I still want you to try. If you look around, there’s not many bright stars over in this part of the sky at all. In fact, Procyon if you simply draw a line down towards the north-western horizon, there’s just one other nearby bright star. Join the dots and what do you get? Well, in my opinion, you get a straight line, but supposedly those two stars, join them together, and you get the smaller of the two Hunting Dogs of Orion.
Orion is well and truly gone at this time of year, so we have no chance of seeing him. And his hunting dogs, the Greater and the Lesser Dogs are also probably getting a little bit too hard for us to see at this particular point in time.
As we continue around towards your right, and that is taking us up towards the north-west, we come up against the first of our zodiac constellations, and that is Cancer the Crab. But sadly you have absolutely no chance of seeing Cancer. It’s a very dim constellation. It was significant in the past, thousands upon thousands of years ago, because it was the position of the solstice.
The Sun would seem to glide sideways in relation to stars in this part of the sky, so they named it after an animal that seemed to walk sideways. Fairly logical conclusion, Cancer the Crab. Unfortunately, you just can’t see much of it.
We’re going to skip Cancer and head around a little bit further and slightly higher, and we’re going to one of the oldest and most famous of all constellations, Leo the Lion. What you’re looking for in this part of the sky is pretty much one relatively bright star, which is called Regulus. It’s one of the four royal stars. Now this is an idea that dates back several thousand years to an area between those magnificent rivers, the Tigris and the Euphrates. Yes, we’re talking of the area – Mesopotamia.
Thousands of years ago, for most of our modern civilizations, we can trace our roots back here, if you like, to the birth of science, the birth of philosophy. Many wonderful things came from this area. What people noticed was that the vernal equinox had occurred in the constellation Taurus the Bull, which we can’t see at the moment. Near this star that we’re looking at at the moment, Regulus, was the summer solstice. By this stage it had drifted from Cancer the Crab into Leo the Lion.
This bright star became the second of the four royal stars, along with Antares in Scorpius, which was the marker for the autumnal equinox, and Fomalhaut in the constellation Pisces Austrinus, the Southern Fish, for the winter solstice. In the past four very famous stars.
But at the moment, we’re looking at Regulus, the brightest star in the constellation of Leo the Lion. It’s upside down for us in the Southern Hemisphere, so try and find an upside down question mark. You’re well on the way to seeing the fiery mane and the chest of Leo the Lion. Once you’ve got that, and you let your imagination go wild, you should be able to see a fairly majestic looking cat sitting there, albeit upside down.
I’ve already mentioned Cancer the Crab, the Greater Dog, the Lesser Dog, and Leo the Lion. These are, of course, constellations. And constellations have been around…. well, we don’t know how long. We can trace most of the zodiac (all bar one) back to the time of Mesopotamia. We’re talking about several thousand years ago.
The first person we think to actually put together a list or a catalogue of these constellations – they’re simply pictures in the sky – was Claudius Ptolemy, a Roman citizen of Greece, nearly 2,000 years ago. And he made up a map or a chart of 48 constellations, including all the zodiacs and some of the other ones. But, not too far into the south.
Over the last 2,000 years, we’ve been updating this catalogue. This was only completed in the 1930s, much like we break cities into suburbs, we now have 88 official constellations in the sky. This was a fairly clever thing to do. Depending on your age and your eyesight and where you’re viewing from, you may be able to see as many as 2,000 stars. It’s pretty much impossible for any one person to remember the position of 2,000 individual pinpoints of light.
If you make up simple stick figures, dot-to-dot figures and tell an interesting story about them as a form of memory aid, you’re far more likely to be able to remember the key areas. And the key areas were, I’ve already mentioned them and I’ll mention them again, because they are so significant: the two solstices and the two equinoxes. You just add a few other stories in for navigation and for timing, to work out markers as we’ve already indicated with Sirius the Dog Star, and you have a very effective way of using the stars to navigate by and to work out the time of year.
To the ancient Egyptians, this particular group of stars looked like a lion. Supposedly this idea comes about because, at the time that the Nile River used to flood, lions were fairly common. They would be looking for water, of course, and any slow moving animal or person that happened to be in the way. A time of plenty of water also was apparently a time of plenty of lions. For the more modern but still ancient Greeks, Leo the Lion was killed by Hercules as part of his ‘12 labours’. After this, of course, his body was put into the sky.
Continue around towards the north after Leo, and about one handspan away, maybe a little bit further, we’ll come across the constellation that looks like a crow. Well, actually, I don’t think it does look like a crow. It is supposedly called Corvus the Crow, but to me it looks far more like a shopping trolley than just about anything else.
It’s fairly high up at this time of year, so looking pretty much due north, look for a group of stars. There’s only about four of five of them, in a relatively small area. If you see anything that looks like a shopping trolley, then you’ve happened upon Corvus the Crow.
This raises an interesting point. You see, the constellations in the past were named after common ideas, common occurrences, animals, beasts of burden, for example, Taurus the Bull…. Stories that would be useful or common to your daily life. But these days, with smartphones, tablet PCs, cars, aeroplanes – some of these things look more like modern images.
I don’t think it’s unfair to say that Corvus looks like a shopping trolley. I just hope that it never becomes officially anything as boring as a shopping trolley. But if your imagination requires it to be so, then so be it.
Slightly below Corvus, which is pretty high overhead and towards the north-east, we’ll see another one of the famous Zodiac constellations. Unfortunately, it doesn’t have any particularly bright stars, bar one. This particular constellation is Virgo, goddess of justice, although there are different ideas about the story behind Virgo.
Virgo is now home to the autumnal equinox. The equinoxes are the two points where the celestial equator and the ecliptic cross. So for us in the Southern Hemisphere, the autumnal equinox is indeed the spring equinox. You’ve got to remember that most of these things were named for the Northern Hemisphere, so for us it’s not only upside down but back to front in the south.
I’m sure that most people recognise that Virgos are indeed the nicest people on the planet. Hmm, I might get a few emails about that statement. You see. That’s something akin to astrology. Astrology and astronomy don’t always see eye to eye, but we do when we’re considering the positions of the stars in the sky. Sadly, Virgo doesn’t have any really bright stars, apart from one, which is the brightest star in the constellation called Spica. It represents an ear of wheat, the symbol of fertility.
There’s much debate as to what Virgo actually represents. To the ancient Greeks, Virgo represented the goddess of the harvest and of justice. She would use the scales to weigh the good and evil deeds, but eventually she became so disillusioned at our bad behaviour that she returned to her point in the heavens. In ancient Egypt, Virgo was seen as the goddess Isis and is claimed to have formed the Milky Way by dropping numerous heads of wheat into the sky. Although Virgo is not a particularly bright constellation, it’s fairly famous. It looks pretty like a very large, Y shaped group of stars if you use the old dot to dot idea.
As we head around towards the east at this stage, we come across the only one of the zodiac constellations – zodiac, by the way, means ‘circle of animals’ – that is not a living animal. Have you figured it out yet? It is, indeed, the constellation of Libra. Libra is the only one of the zodiac constellations not to have originated in Mesopotamia. It seems as though people knew of it, but they didn’t actually give it a separate, independent status for quite some time, and the stories that we now have probably come from ancient Egypt.
It’s reported to have been the balance, or the scales, that weighed between the upper and the underworlds. It’s usually represented as a human figure holding the scales, except in Arabic astronomy. Apparently it’s not acceptable to make representations of human figures, so quite often it was simply drawn as scales and left the human figure off. Around the time of Julius Caesar, it actually became popular to draw Julius Caesar holding the scales, but this was later dropped and simply returned to being the scales of justice.
The really interesting thing about Libra…. there’s not much to it. There’s really only three bright stars. But goodness gracious me! I just love the names of the stars in this constellation. These stars were never really their own separate, independent constellation. They used to be considered for some stage, as being part of the scorpion. Scorpius as we call it today.
The old Arabic word for scorpion is ‘Zubana’. We have three bright stars in Libra, and they all have that as part of their name. The brightest star in Libra is called Zubenelgenubi. It means ‘the southern claw of the scorpion’. The second brightest star in the constellation of Libra is Zubeneschamali, meaning ‘the northern claw of the scorpion’. I like Gamma, or the third brightest star, Zubenelakrab. My pronunciation is probably quite poor, but it means ‘the scorpion’s claw’.
This raises an interesting point. The sky is one of the best examples of multiculturalism I think you’ll ever come across. You have stars with Arabic names. You have stars with Greek and Roman stories behind them. Just about every culture on the planet has stories and uses them to work out the time of year and to work out the cardinal directions. Some of these names, as I’ve just discussed, are actually quite intriguing and quite beautiful.
You also should consider, looking at Libra: is it the pair of scales that can weigh up good and bad, or is it simply a fairly good looking triangle? Take away the imagination and, yes, it’s nothing more than a triangle. But with the imagination, I’m sure we can all see the scales of justice. That’s something that’s well worth remembering as we look across the sky: imagination. It is such an important thing to have.
As we look below Libra, towards the east, we come across a rising constellation. It’s one of the only constellations that looks like what it is supposed to be. And yes, it is indeed Scorpius, but not Scorpio. Scorpio is its astrological name, and in astronomy we prefer Scorpius.
At the heart of Scorpius, you should be able to see a fairly bright orange, reddish looking star. Now, when we say red, please don’t expect traffic light red. It’s nothing like that at all. It’s more of a golden yellow, orangeish looking star. And that is the brightest star in Scorpius. It’s called Antares. It’s one of the four royal stars, dating back many thousands of years ago, that was used as a place marker for the equinoxes and the solstices.
This star, this dying red supergiant, about 600 light years away and 15 times the mass of the Sun, at about 800 times the diameter. So, goodness gracious, it’s a big star. Its name? Anti Ares. Hmm. Antares. Antares, Anti Ares. Anti Ares means ‘the rival or competitor to the planet Mars’. You see, every now and then, the planet Mars comes fairly close to this star, and they look fairly similar. As a result, the star was named as a rival to Mars: Anti Ares, Antares. What a great name.
When you look at Scorpius, if you have a star map there, I’m sure you’ll be able to make out the claws of the scorpion. The red star Antares now represents the heart of the scorpion. You leave its short body, where the heart is, and then you can see a long, curved line of stars that makes its way around to become the sting.
Now, there are many different legends about Scorpius, and they typically also relate to the opposite constellation in the sky, and that is Orion the Hunter. One particular story has that the hunter Orion, who’d boasted that he could kill any animal on the planet, was going out and becoming, well, over familiar with the goddess of the hunt, Artemis. Her brother, Apollo, was not particularly keen on this, and as a result he sent the giant scorpion to attack and kill him.
There are many versions of this, and they don’t always end in exactly the same way, but they do in terms of: Orion dies and after some mourning his body is placed in the sky directly opposite that of Scorpius. So, if you can see Scorpius coming up in the east, as we can at the moment, there is effectively no chance of seeing Orion, as it’s already set.
The beautiful thing is that Scorpius sits near the centre of the Milky Way galaxy. That’s our galaxy as we see it from here. The actual centre of the galaxy is just below the tail of the scorpion and near the next of the zodiacs that is rising at the moment but a little difficult to see, and that’s Sagittarius the Archer. Sagittarius is too low for us to see clearly at the moment, so we might have to wait a little bit for that.
But just below the tail of the scorpion, roughly 26,000 light years away, is the centre of the Milky Way. And what would be there at the centre of Milky Way but Sagittarius A *. Sagittarius A *? What an unusual name. What is it but a super massive black hole. A black hole that’s roughly four million times the mass of the Sun. Although that seems rather large, only recently astronomers have discovered other, much larger supermassive black holes, hundreds of millions of times bigger than the Sun.
By the way, if you ever get an opportunity to visit a black hole, don’t go! For what awaits you is the very painful, yes, somewhat irreversible process of spaghettification. Which means, if you get too close to a black hole and you cross the danger point, which is called the event horizon, you are going to eventually be ripped apart, atom by atom. Not a particularly nice way to go, in my opinion. Forgetting spaghettification, the area around Scorpius is well worth looking at and exploring with a small telescope or a pair of binoculars.
I’ve said quite often, you don’t need an expensive telescope or even need an expensive set of binoculars. Just an ordinary pair of 7 x 50s. The trick is you need to be able to hold them still, either by mounting them on a tripod or, if you like, resting them on a pillow sitting on top of a fence or against a tree or against the side of a building.
If you do that you’ll get a much steadier view. The area of the Milky Way around Scorpius is an absolutely gorgeous place to look. There are some lovely clusters. As well such as M6, often called the Butterfly Cluster, and M7, another open cluster. These are basically just little clusters of young stars that have formed relatively recently.
By the way, we’ve mentioned the Milky Way but have you ever wondered why we call it the Milky Way? The best thing is that here in the Southern Hemisphere the Earth is tilted to one side by 23.5 degrees. That 23.5 degree tilt, which is the reason behind the seasons, gives us the best view of the Milky Way.
For us in the south it pretty much passes very nicely high overhead, but for the major population centres in the Northern Hemisphere the centre of the Milky Way never gets that high up. The higher it is the less atmosphere you have to look through, the better the view. Milky Way. Via Lactea. One particularly famous story is the goddess Hera was breastfeeding a young, discarded baby that she’d found…. until she was told that it was the illegitimate son of her god husband, Zeus.
When she found out about this she ripped him away from her breast and milk squirted across the sky to form Via Lactea, meaning ‘by milk’. Once we’ve had a look at Scorpius and explored this area with our binoculars we’re going to continue around towards the south and high in the sky you’ll see the smallest of all 88 constellations. This is the best time of year to see it.
It is the group of stars that’s on the flag of Papua New Guinea, New Zealand, Micronesia. It’s also on the Brazilian flag, although you have to look fairly had to see it there, and there’s one other country. Yes, of course. It’s us. The group of stars is the Southern Cross. It represents a Christian cross.
You see, when European sailors started coming into the Southern Hemisphere in the 1500s they were somewhat nervous. To see a symbol that was so clearly identifiable with Christianity made them feel good so they named it the Southern Cross. It didn’t officially become its own constellation until the 1930s when the International Astronomical Union finally completed the division of the sky into 88 separate regions or constellations.
The Southern Cross is not only significant for us in the Southern Hemisphere, it’s bright. It’s got three of the top 30 bright stars in it. It’s small, so it’s conspicuous. It’s also very useful. At the moment I think most people would agree the Southern Cross is standing up. If you were to draw an imaginary line through the top of the cross through the bottom, the top star is the third brightest. It’s called Gamma Crucis, through the bottom star, which is the brightest, called Alpha Crucis.
If you extend a line through the bottom four and a half times that length you come to a fairly empty part of the sky. There are no bright stars there. That empty part of the sky is the south celestial pole. This is the point around which all the stars in the sky rotate in the Southern Hemisphere. It’s like the hub. The centre. Throughout the night the Southern Cross and all the other stars will rotate around this point.
The beauty is the Southern Cross will always point to this one point. It doesn’t matter what time of year. It doesn’t matter what time of night. If you draw a line from the top of the Christian cross through the bottom, extend it by four and a half times its length that will take you to the south celestial pole in the sky and that is south. Simply drop straight down to the ground from that point and there you’ve got south.
If you’re looking south, to your left will be east, to your right will be west, and directly behind you is north. There you have it. One of the most, if not the most, important uses of the stars: finding your direction. I’ve mentioned that the Southern Cross is significant for us in the Southern Hemisphere. Yes, it is. In New Zealand the Maori culture sees it as ‘Te Punga’, representing a boat anchor.
For a truly diverse and rich and beautiful group of stories, you need go no further than the Indigenous people of this land. The Aboriginal people of Australia have been here for longer and telling stories from generation to generation longer than any other culture on the planet. These stories of the sky are the oldest. It’s something we should all endeavour to learn.
Let me tell you one about the Southern Cross. This story I’m about to tell you has been told to me by the Indigenous Curator at the Powerhouse Museum, James Wilson-Miller. This is a story that was documented first around about 1896 by K Langloh Parker. This version has been given to me by James as I’ve mentioned. It goes something like this.
In the very beginning of time there was a great spirit in the sky by the name of Baiame. He walked on the Earth and the red ground of the ridges and the plains. He made three people, two men and one woman. When Baiame saw that they were all alive and well he told them what animals and plants they could eat and which ones they shouldn’t eat.
After a long period, everything was going quite well. There came a period of a long, dry spell and nearly all the plants and animals died out. One of the men got so hungry he killed a small kangaroo rat, cooked it, and gave some of it to the woman to eat. She enjoyed it. Both of them offered the meat to the other man but he refused to eat it. They kept offering time and time again but he refused and got annoyed with them and started to walk off in a direction away from the man and woman eating the kangaroo rat.
When they finished eating, they looked up and they saw that he’d gone, so they walked off after him. They walked over the hills, the pebbly ground, until they found him at the edge of a big coolabah plain near the side of a big river. He was weak from hunger but he would not stop. They called out to him but he kept walking. He walked and walked until he came to the side of a big gum tree and there he fell to the ground, dead.
Right next to him, the man and woman could see a huge, big, black figure with fiery eyes. It lifted up his body and put it into the hollow of the tree. The man and woman ran towards it but there was a great crack of thunder and they fell to the ground, startled and stunned. When they looked up they saw the black figure of the yowie lifting the tree upwards from the ground and carrying it into the southern sky.
They could not see their lost friend any more but only the two fiery eyes of the Yowie as it continued up into the sky. They suddenly heard the raucous shriek of two Mooyi, two sulfur crested cockatoos flying up into the sky after the tree. On and on the spirit went up into the sky with the two Mooyi shrieking, flying after it, trying to get into their tree.
Finally the tree was so far away they could barely see it and it planted itself next to the Milky Way in the sky. The tree was so small they couldn’t see it any more but they could see the eyes of the Yowie and the eyes of the first man who had died. Those four stars became the four brightest stars in the Southern Cross. The two Mooyi, the sulfur crested cockatoos, are still chasing their tree and can be seen next door as the stars Alpha and Beta Centauri, the bright Pointers that point toward the Southern Cross.
That’s a story from the Murri people from the northern New South Wales region and the south-east area of Queensland. There are many other stories around this beautiful land of ours with something like 500 different Aboriginal groups around Australia. There are many different versions of stories about the Southern Cross.
We’re fairly high in the south at the moment talking about the Southern Cross and its rich history but you know what? It’s also a spectacular place to go hunting with a pair of binoculars. Again, and I can’t state it enough, you must make it steady otherwise your tired arms will start to vibrate and you will shake up and down. You won’t be able to see the beauty that’s hidden up there just waiting for you to have a look at it.
Go from the Southern Cross, which is high in the south. I want you to drift down towards the second brightest star in the south sky, you ought to be getting quite low in the south-west at this particular point in time, and that is Canopus. Canopus is a fairly hot, big star. It’s about 20,000 times brighter than the Sun but at 310 light years away that means it’s only the second brightest star in the night sky after Sirius, the Dog Star, but that would be now quite low in the west. They’re both getting harder to see.
This whole area, from the Southern Cross down to Canopus, is well worth a look as you traverse what was the largest of all the constellations, Argo Navis. The ship that carried Jason and the Argonauts in search of the Golden Fleece. It’s too big and as a result it’s often broken up into four smaller constellations: Carina the keel, Puppis the deck, Pyxis the compass, and Vela the sails.
This whole area is well worth a look because there are so many beautiful things to see, even with a small telescope or a small pair of binoculars. Actually, I should go back to the Southern Cross. If you look at the Southern Cross, the bottom star at the moment, Acrux, I want you to go around in a clockwise direction. The next star would be on the upper left is Beta Crucis. If you’ve got a pair of binoculars train your binoculars onto this star, Beta Crucis.
If you do so, just to the side of that and down a fraction you’ll be able to see a young group of stars, an example of an open cluster. An open cluster is a very young group of stars all formed at the same time from the same cloud of gas and dust. They’re at the same distance from us. It is a very good example of a controlled situation. The only key variable that we have is mass and that variable is, to some extent, the most important of them all.
This group of stars you’re looking at, this little cluster, is called NGC4755, or New General Catalogue Object number 4,755. Its common name I think is far more beautiful and that is the descriptive name of the Jewel Box. If you look at this young group of stars you’ll see round about 100 of them. They’re somewhat more than 6,000 light years away. Most of the stars are white. There’s some with a slightly bluish hint. But there’s also one which is very clearly red. It’s not traffic light or laser red, but it’s golden, yellowish orange.
You’ve got all different colours there, and it looks like a fine piece of jewellery laid out on black velvet, hence the name, the Jewel Box. The Jewel Box is probably the second most beautiful open cluster of stars. The most famous, and perhaps the most beautiful, is that of the Pleiades, M45, or Subaru, in the constellation of Taurus the Bull, but that’s not visible at this time of year.
Scanning from the Jewel Box in the Southern Cross, down towards Canopus, which is getting low in the south-west, you’ll see some spectacular sights. It’s a very rich part of the Milky Way. There are lots of clusters there to be seen. Take your time. Enjoy the view. It’s well worth the effort.
Before we leave the Southern Cross, we should actually make note of one more aspect. Again, go to the brightest star of the cross, which is at the bottom, look to where we just were, looking at Beta Crucis on the left, and if you’re away from the city and there’s no Moon, you should be able to see that there’s a dark patch against the Milky Way. This dark patch is often referred to as the nest of an eagle. You see, some Indigenous communities see the Southern Cross as being the footprint of an eagle. We’ve got the nest of the eagle snuggled up against the footprint. The two bright Pointer stars, Alpha and Beta Centauri, nearby, represent a throwing stick that was used to smack the eagle in the head.
However, there’s another way of looking at it, and that is to look at the dark patch that is the coal sack or that eagle’s nest. If you look carefully, you’ll see that that dark patch extends its way back down towards the east, towards the constellation of Scorpius.
I believe that there are only two key groups of people in the world that actually look at pictures in the sky made up of a lack of stars, and they are the Incas of South America and some Indigenous communities of Australia.
Look for this lack of stars, extending from the Southern Cross back towards Scorpius, and you may just be able to see the outline of an emu. The coal sack up against the Southern Cross represents the head. It’s fairly easy to see. Then you’ve got a long, slender neck of darkness which suddenly gets a lot broader in the area of Scorpius, and that represents the body of the bird.
If you can make it out into the countryside and see this, it’s one of those ‘aha!’ moments and well worth the effort. We’ve all spent so much time trying to see pictures in the sky by joining the dots and using our imagination, but in this particular instance, it’s the lack of stars that make up a picture.
Oh, by the way, intriguingly, if you can make it to the Ku ring gai Chase National Park just north of Sydney, you’ll actually be able to see a carving of an emu on the Elvina Track. It’s remarkably like this lack of stars that I’ve just been describing from the Southern Cross down to Scorpius. But please, make sure you check with National Parks and Wildlife before you go into the park. Make sure you treat the carvings with the utmost respect that they deserve because they are truly spectacular things to see.
Wrapped around the Southern Cross, and high overhead at the moment, is the large constellation of the Centaur: half man, half horse. There are two centaurs in the sky. One of them I’ve already mentioned, coming up low in the east, is a little bit too hard to see at the moment. That’s Sagittarius. But the higher of the two and the easier to see, wrapped around the Southern Cross, is that of Chiron. Chiron was a particularly nice fellow, apparently. He was a tutor, or a teacher to fabulous characters in mythology: Achilles, Hercules, and Jason from Jason and the Argonauts.
It is, nonetheless, hard to see a half man, half horse. But if you can see the Mooyi, the sulphur crested cockatoos that I mentioned before that were chasing the tree into the sky, Alpha and Beta Centauri, they represent the front legs of the horse. From there we simply see a stick figure that wraps all the way around the constellation of the Southern Cross, and you can pretty well see the half horse part.
The half man part, holding a spear, supposedly pointing towards the scorpion, is a little more difficult, but as long as you’ve got your sky guide, I’m sure you’ll be able to see it, and it’s well worth the effort.
As we’ve already mentioned, you are heading down from the Southern Cross, which is placed high in the south at the moment, heading down towards the south-west. You will pass through the constellation of Carina the Keel. I’ve said this is a really good area to look at, and I should also point out that there’s something rather spectacular going on in this constellation.
It’s not visible to the naked eye, but there’s a star there called Eta Carinae, which in the 1840s was just a relatively dim, background star. But in 1843 this star, because of its nature, a cataclysmic variable star, underwent a precursor to detonating as a Type II supernova. It shed something like 30 solar masses of material and flared up.
By 1843, it was the second brightest star in the night sky. Now, the Boorong people of the Wergaia language group in the north-west of Victoria were able to see this, and they incorporated it into their Dreaming. They named it Collowgullouric War, which means the ‘Wife of War’, represented by the star Canopus to most of us these days. That’s well worth a look. It’s a beautiful part of the sky to scan.
As we scan towards the right again, we should be able to see Sirius, where we started our tour of the sky for the month, but it will be getting down quite low and perhaps by this stage may have set altogether.
Highlights for June 2012. Let’s start with the Moon. On Monday 4th June, the Moon will be full at 9:12pm. Monday 11th June will be the last quarter Moon at 8:41pm. Wednesday 20th June, the Moon will be new at 1:02am. And on Wednesday 27th June, it will be first quarter at 1:30pm.
The winter solstice, the point at which the Sun appears to stand still in the sky, will occur on the 21st at 9:09am.
There will be a partial lunar eclipse on 4th June. It will start at 7:59pm and will end at 10:07pm, with just 38 percent of the Moon being covered by the Earth’s shadow.
By mid month, the planet Mercury will appear in the constellation of Gemini, low in the west, shortly after sunset, and will move to the constellation of Cancer by the end of the month. On 21st June, the thin crescent Moon will be below and to the left of Mercury, and on the 22nd, the Moon is just above the planet.
Mars is high in the north, in the constellation of Leo, and then moving into Virgo later in the month. And on June 26th, the Moon is just above and to the left or the west, of the planet Mars.
Saturn will also be in the constellation of Virgo and will be near the Moon on the 1st and then again on the 28th. At 6:00pm on 27th June, the first quarter Moon, Mars, and Saturn are all very close together. And this is a fabulous opportunity to get a great photo, so make sure that you don’t miss it.
The main event for June 2012, and the main event for the entire year, is the transit of Venus. Transits of Venus occur about 100 years apart. There’s something like a 240 year cycle, but it’s a bit complicated. The last transit of Venus was in 2004. We have one this year on the 6th of June. If you miss this one, you’ve got to wait until 2117 and then 2125. Yeah, I don’t like your chances.
Make sure you see the transit of Venus on the 6th of June this year. Sydney Observatory will be conducting live viewing of the six hour event, from 8:16am Eastern Standard Time through to 2:45pm. Australia, New Zealand, and most of Asia and Alaska, are perfectly positioned to see the transit of Venus this time.
It was first observed in 1639 by Jeremiah Horrocks near Liverpool in England. Then in 1716, the Astronomer Royal, Edmund Halley, predicted that there was a transit coming up in 1761. By using Kepler’s third laws of planetary motion you could actually work out the distance from the Earth to the Sun. If you could do that accurately, you’d also be able to work out the distances for every other planet in the solar system to the Sun and therefore the scale of the solar system.
Don’t forget that you can download your map of the night sky at www.sydneyobservatory.com.au. You can purchase your copy of ‘The Australasian Sky Guide’ by Dr Nick Lomb from Sydney Observatory, the Powerhouse Museum, good booksellers, and from the Powerhouse shop online. You can also subscribe to our Sydney Observatory monthly sky guide podcast on iTunes.
My name is Geoffrey Wyatt. I’m the Senior Astronomy Educator at Sydney Observatory, and I hope you’ve enjoyed your tour of the June 2012 sky.