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, Astronomy Educator at Sydney Observatory.
Geoff’s enthusiasm and humour are captivating but based on sound science, and enriched with stories of historical and cultural aspects of astronomy, including Indigenous and Greek myths. According to some Indigenous communities, there is an Emu in the sky (see picture, below).
Geoff reckons that June is a great month to see the brightest part of the Milky Way high overhead. So go on, get a blanket and a torch with red cellophane on the front, your free sky chart and audio (below) and go outside, and look up at the wonder of the Universe.
SEE THE SKY CHART
We provide an embedded sky map (below) and a June 2015 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 2015 Australasian sky guide’, by Dr Nick Lomb has more information and star maps for months from December 2014 until December 2015 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 2015 monthly sky guide audio
Geoffrey Wyatt: Boodyeri kamaru. That’s “Hello there” in the language of the Gadigal people of the Eora nation, the traditional custodians of the land upon which Sydney Observatory was built in 1858.
My name’s Geoffrey Wyatt. I’m one of the Education team here at the Museum of Applied Arts Sciences’ Sydney Observatory, and I’m going to be talking to you about what’s in the sky for the month of Junius, the fourth month of the old Roman calendar as created by Romulus around 735 BC. After Julius Caesar’s last year of confusion and reform in 46 BC, it became the sixth month of the year, June.
This audio guide, the transcript and printable sky map are all available free from our website at Sydney Observatory, Monthly Sky Guides.
I recommend that you use a printed map to help you navigate the night sky. You could use the free downloadable one from our website, or one from the Sydney Observatory book, ‘The Australasian Sky Guide’, by Dr Nick Lomb. I’ll give you more details about that at the end of the podcast.
In my opinion, the month of June each year is the best time of the year to go outside, as long as it’s clear and you are warm, to look up and enjoy the view of the Milky Way as it rises in the East and passes overhead.
As we head toward the longest night of the year, the winter solstice, clearly you’ve noticed it’s cold. If you’re going outside to look at the stars, you will need some supplies.
The obvious ones are a blankie to sit on so you don’t get wet. A torch, hopefully with red cellophane or a red light, but if you get the cellophane make sure it’s not the water soluble stuff. You might also need to have a cup of tea or perhaps a hot Milo as well.
What you need to do is to find yourself a vantage point, somewhere where you’ve got as clear a view as possible of all four cardinal directions, North, East, South and West. I know that sounds obvious, but many of us live next to big buildings, trees, hills, in valleys – so we don’t get a clear view.
But to get the best advantage from the night sky guide, the higher you are, the more of the horizon you see, the better.
You’ll also need, some would argue, the second most powerful tool in the Universe after mathematics, and that is imagination. When we look at the patterns in the sky, some of them are obvious, many are not…Imagination will unlock the patterns and bring the stories alive. So we’re warm, we’ve got supplies. Are you ready to go?
Wait for sunset, then a little bit longer, and a little bit longer, until it’s relatively dark. A slight hint of twilight in the West is okay, and that’s a good thing, because that will help you orient yourself and get the right positions.
What I want you to do is turn to an azimuth of 270 degrees. Azimuth? Let’s run through that very quickly. Astronomers like to find positions in the sky. Of course, we could say, “Over there, by the tree, to the left,” or “Up a bit”. But unless you’ve got the same reference point, that doesn’t work. So you need a universal way of doing it.
We’re going to use azimuth, an angle that we measure in a clockwise direction as seen from above starting north. Find North. Have you got it? Good. We can say that’s zero degrees azimuth.
Turn to your right a quarter of a turn. You should be facing east; it has an azimuth of 90 degrees East of North. Do another quarter turn. You should be facing south, an azimuth of 180 degrees. Turn to your right one more quarter turn; you’re now facing west, an azimuth of 270 degrees.
That’s easy. How about upwards from the horizon? Well, directly overhead at zenith is 90 degrees. Halfway up, 45 degrees. But the first object I want you to have a look at is an azimuth of 270. OK, good, we’re facing west. But 20 degrees above the horizon? How can you do that?
Simply hold out your hand at arm’s length as far as you can stretch. Hold out a pinkie. Now that pinkie, measured against the sky, will be 1 degree, or twice the size of the full moon. Clench your fist. That’s 10 degrees against the sky. Now spread your hand from pinkie tip to thumb tip is about 20 degrees, and it doesn’t matter how old you are, how tall, how short, whatever. It’s all in proportion.
Look west, one hand span above the horizon. You should be looking for the brightest star in the night sky. One of his names, Warepil. Don’t forget that people from all around the world have different names for different objects and therefore this is a great time to point out that the oldest star watchers on this planet are the Indigenous peoples of Australia. To the people of North-Western Victoria, the Boorong clan of the Wergaia language group, this star is one of the group that we now refer to as the Nurrumbunguttias. Perhaps ‘old spirits’ is perhaps a better way to describe them. The old spirits went into the sky and The Milky Way that we now see is the smoke from their campfires. We call that Warring. To other Aboriginal communities including the Kamilaroi and Euahlayi from North Western NSW the Milky Way is Warrumbul.
Let’s get back to Warepil. But to you and me, he’s more commonly known as Sirius the Dog Star, the brightest star in the night sky.
This star is not as bright as you would have seen it some months ago because it’s getting very low in the Western sky. So, it’s not a good time to see it but it does make a good starting signpost.
Sirius is 8.6 light years away, about twice the mass of the Sun, nearly twice as wide and about 25 brighter. By the way, a light year is the distance that light travels in one year. It’s a long, long way. For those of you that like numbers, it’s about 9.5 thousand billion kilometres. It’s a long way but you don’t take my word for it, try this. It’s 300,000 kilometres per second in the vacuum of space. Multiply that by 60 seconds in a minute, 60 minutes in an hour, 24 hours in a day, 365.25 days in a year. That will give you the distance of one light year.
If this star is 8.6 light years away, that means we see it – as it was more than 8.5 years ago. You’re looking back into time and Sirius is relatively close star, but for other objects, goodness me. You’re looking back so far, you’re seeing them as they were at the time of the dinosaurs and beyond! Sirius, setting in the West, brightest star in the constellation of Canis Major the big dog.
You’ll hear me mention this time and time again. A constellation is simply like a suburb in the sky, a signpost, a group of stars that helps us find our way. They’ve been used for a long, long time. We now have 88 of them officially. The oldest ones probably go back maybe 4,000 years ago or so.
By the way, the Egyptians used to look at Sirius and work out the length of the year. From many, many, years of observation, they were able to work out, on average that the length of the year was 365.25 days.
They didn’t understand decimals. In fact they didn’t even have decimals. But I’m sure anyone can figure out a quarter. Imagine a cake and you can cut it in half, you can cut it quarters. You may be able to cut it into thirds. When you start to get down to the very small fractions, which we commonly use as decimals, that’s trickier. But a quarter? That’s easy.
How accurate were they with the length of the year by the way? To within 11 minutes of what you and I accept it now and I think that’s truly amazing.
Let’s get back to Sirius. We’re going to say farewell. Turn to your right ever so slightly so that we’re heading toward the North-West. You should be able to see another reasonably bright star close to the horizon. That star is called Procyon though some call it Proc-y-on. It’s the brightest star in another group of stars called Canis Minor smaller of the two hunting dogs.
Canis Major, Canis Minor they are the dogs that used to go with Orion the mighty hunter. He’s already well and truly set in the West, and we won’t see him for several more months.
Continue now towards the North-West a little bit more. You’re going to look for a group of stars, the faintest of all the constellations of the zodiac – that is, the path of the animals that most of us are familiar with, our birthday star signs, if you like.
This particular constellation is really, really hard to see at the best of times. Trying to see Cancer right now? Forget it. I don’t think you’ve got much of a chance which is a shame. It’s an interesting group of stars because the picture is so old.
It is a crab that walks or slides sideways. It used to be important to the people of Mesopotamia thousands of years ago, maybe back as far as 4,000 BC. This was the part of the sky that the summer solstice for the Northern Hemisphere used to occur in, but no longer. The Earth does a rather unusual wobble. It takes 26,000 years to wobble through a cycle once, which we call the precession of the equinoxes.
Things change ever so slowly. Cancer? Nah, you’re not going to be able see it now. It used to be a marker in the sky for the summer solstice for those in the Northern Hemisphere, but no longer.
Towards the North North-West, a little bit more to your right, at an azimuth of roughly 320 degrees and an altitude of 40 degrees two hand spans up and you’ll see a group of stars that with a little imagination, or perhaps a lot, you may be able to see an upside down question mark. Can you see it? You might need the map. Look for the question mark which is part of a figure that looks like a cat. What you’re looking at is perhaps one of the oldest of all the constellations. Leo the lion.
The brightest star that you should be able to see at this particular point. As I mentioned, about 40 degrees above the horizon, is the little king, Regulus. It’s a star that’s about 79 light years away, so again you’re looking it now as it was about 79 years ago. You’re looking back into time.
Some people call this star the second of the four Royal Stars. Thousands of years ago, for the region near Mesopotamia, this star, Regulus, was seen as the brightest star near the point in the sky known as the summer solstice. It was actually as I mentioned in Cancer the crab but that doesn’t have any bright stars. This was the nearest bright star.
They used this star as a marker. They called it a Royal Star. Of course, it’s no longer a marker, because the solstice and the equinoxes have moved, but historically, this star is important as was the constellation of Leo which we know is old. It was mentioned in the 8th century BC by the poet Homer in his fabulous poem, the ‘Odyssey’. It’s another one of these constellations in what we call the zodiac, the circle of animals.
We also know the astronomer Claudius Ptolemy looked at this group of stars. He was a Greek who lived in Alexandria, around about 150 AD. He included it in his book, the ‘Almagest’, where he listed 48 constellations. Ever since then, we’ve used those and tagged on a few extras to come up with 88 that we have now.
As we leave Leo the lion and head towards the next of the zodiac constellations, this part of the sky is absolutely ripe for the pickings if you have a small telescope or a good pair of binoculars but you’d need them on a tripod.
Sadly, none of these next few objects are visible to the naked eye, but it’s worth a try.
Go from the tail of the lion marked by the star, Denebola and head towards the next constellation Virgo. We’re actually after a star called Vindemiatrix, which means the ‘grape gatherer’. It’s not exactly the brightest star in this part of the sky, but you should be able to find it if you’ve got your star map.
In this region, there are around about 2,000 galaxies crowded together in something called the Virgo galaxy cluster and up to a distance of about 65 million light years away. As far as telescopes go, you’d need something at least 100 millimetres in diameter preferably bigger, a good eyepiece, a dark viewing location NOT in the city and no Moon. I can’t stress this enough.
After scanning for galaxies if go up a little bit higher you may be able to see a group of stars that looks a little bit like a shopping trolley? Can you see it? It’s almost overhead, but not quite. This group of stars represents the constellation Corvus the crow. The crow used to be able to talk, according to some legends, but he was a pretty lazy bird and didn’t do a good job, so the Greek god Apollo eventually lost his temper, took away his ability to speak, and banished him into the sky.
As I say, to me, it looks like a shopping trolley, but historically, Corvus the crow. This area of the sky houses one of the easiest galaxies to see with a pair of binoculars. It’s called M104. It’s commonly called the Sombrero Galaxy because it looks a bit like one of those huge hats.
It’s a little bit smaller than the Milky Way, but moving away from us at 1,000 kilometres per second, which is truly astounding. It’s about 29 million light years away. It’s very small, but certainly well worth a look if you have a telescope or a good pair of binoculars. M104, the Sombrero Galaxy in Corvus the crow. The ‘M’ in the name refers to a catalogue developed by a Frenchman, Charles Messier, who made up a list of objects that you wouldn’t waste your time on if you’re trying to find a comet. We now actually use those as a bit of a signpost. Of course they’re also quite interesting in their own right.
From Corvus, go back down a little bit towards the constellation of Virgo with its one bright star, the 15th brightest in the night sky, called Spica. This star is about 260 light years away. It’s certainly bluish white. It’s quiet dazzling. It’s about 10 times the mass of the Sun and 7 times its diameter. It’s a very hot, bright star.
You’re in the constellation of Virgo. This is the home of…at the moment, I should say, because I want to re-emphasize that things change… the home of the autumnal equinox, but that’s a Northern Hemisphere event.
For us, it’s the home of the spring equinox. Until the year 2020, the spring equinox will occur on the 23rd of September. A quick refresher? That’s when the Sun crosses the celestial equator from the Northern Hemisphere, back into the Southern Hemisphere, heralding the start of spring.
Virgo, goddess of justice. To the ancient Greeks, she was the goddess of the harvest, as well as justice. She would use her scales to weigh good and evil deeds. Legend says that she became so disenchanted with our behaviour that she threw away the scales and returned to her home in the sky.
To the ancient Egyptians, she was Goddess Isis, who formed the Milky Way by dropping heads of wheat across the sky. There are so many stories about the stars in the night sky. I love it.
Before we go any further, I want you to go down to about 25 degrees above the horizon, towards the North North-East, there’s a relatively bright star there. We call it Arcturus, but through the Indigenous people that I mentioned before, the Boorong of the Wergaia language group, this star represents Marpeankurrk.
Marpeankurrk was a woman who discovered the rather tasty wood-ant larvae. She taught people where to look for them. When the Indigenous people of that region of North-Western Victoria saw that star, Arcturus, in the Northern sky, they knew it was time to go and looking for wood-ant larvae. When they saw Arcturus setting with the Sun, they knew that the season for the ant larvae was coming to an end and summer wasn’t that far away.
After that little diversion, what we’re going to do is go back up to Virgo and head down along the ecliptic, this imaginary line that’s the path of the animals, if you like, towards the next of the zodiacs. This one I must talk to you about with a heavy heart.
This group of stars was briefly associated with Julius Caesar. It showed Julius Caesar holding the scales, the balancing of good and justice, but this was dropped. In more modern Arabic culture, apparently it’s not correct to draw a representation of a person. On many star maps, the figure of Julius Caesar holding the scales was dropped, and it returned to the older group of stars, simply the Scales of Justice.
To the ancient Egyptians, these were the scales that would measure your heart after you had died and that’s where the expression ‘a heavy heart’.
If your heart was heavy with bad deeds, then you weren’t in for a good time in the afterlife, but if not, you’re ready to pass through to the afterlife with safety.
It’s incredible how many expressions we have today that can be traced back to cultures from thousands upon thousands of years ago.
This group of star is quite clearly Libra the Scales. That is the only one of the zodiacs which is not a living animal. It’s not particularly noteworthy, apart from the fact that at one stage, it was also associated with the next zodiac along, Scorpius.
As a result of being made its own constellation, the stars themselves have rather cool names. Roughly 40 degrees above the horizon, we have at the moment, Zubenelgenubi, the Arabic name (I might not have pronounced it correctly), which means the Southern claw of the scorpion. Zubeneschamali, roughly 35 degrees above the horizon, meaning the Northern claw of the scorpion, and Zubenalakrab simply meaning scorpion’s claw.
Those three stars are the brightest stars in that constellation, there’s not much else there. We go down towards the East and Scorpius is coming up high enough for us at the moment to have a look at. Depending on what time you’ve started, you may not be able to see it all.
As the night goes on, you will see more and more of this group of stars that looks like a scorpion, if you use a little bit of imagination, or perhaps an ice pick. All sorts of different representations have been made.
There should be one clearly visible star that is slightly reddish. It’s not traffic light red. It’s not ruby red. It’s more of a golden orange hue. This star, because of the fact that the planet Mars goes past relatively close by every 780 days is called the Rival of Mars, anti-Mars, anti-Aries, Antares.
It is the brightest star in the constellation of Scorpius and is its heart. By the way, it’s not ‘Scorpio’. That’s its astrological name. For us astronomers: Scorpius. This star is 550 light years away. It’s about 15 times the mass of the Sun and 800 times its diameter.
To you and me, all these stars look like little points of light, but when we start to consider their size, the Universe is enormously big and some of the objects in it, wow – huge!
If you have a look at Antares from a dark location, on a moonless night when it’s up a little bit higher, you may be able to see less than one degree away, or the width of one pinkie held at arm’s length, a little fluffy lump of light. That is what we call a globular cluster.
It’s the fourth object in the Messier Catalogue, so it’s simply called M4. It’s a group of very old stars tightly packed together. It is well worth a look, even through a small pair of binoculars. It’s reasonably close at about 7200 light years away and is thought to be about 12 billion years old!
Continue along towards the tail of Scorpius, there’re two other little clusters up there but very different to M4. What we’re looking for here are young clusters, M6, the Butterfly Cluster of about 80 stars, they’re less than 100 million years old. In stellar terms, they’re very young indeed. There’s another group called M7. Both of these open clusters are young, not very many of them, relatively close by. Globular clusters like M4 are old, lots of them jammed together and they’re typically further than open clusters.
If your view towards the South-East is clear enough and dark enough and you’ve waited long enough as we’ve been doing this rather long tour of the June sky, you may start to be able to see a group of stars that looks a bit like a teapot.
It is Sagittarius, the Archer, half man, half horse, with a bow and arrow and the arrow pointing at the heart of Scorpius or the star Antares. Good luck on that one.
The intriguing thing about this part of the sky is that it’s the home to the centre of the Milky Way, Via Lactea, by milk, our galaxy. Roughly 26,000 light years away, in this direction near the spout of the teapot. What lurks at the centre of the Milky Way? In fact, what lurks at the centre of most galaxies? Quite probably a black hole. In this part of the sky we have a black hole that is about four million times the mass of the Sun called Sagittarius A* (pronounced Sagittarius A star). You can’t actually ever see it but wait a little bit longer until it Sagittarius is a little higher as it is a beautiful part of the sky to look at.
Now that you’re facing East, I want you to turn towards your right. That means we’re heading towards the South. Go around towards the South and you’re looking for what is the smallest and perhaps the most famous of all 88 constellations.
Yes, I’m biased. I live here in the Southern Hemisphere. We have the best view of the Milky Way as the Earth is leaning to one side by 23 and a half degrees. That means we get the best of view of the Milky Way.
What I want you to look for a small, bright constellation, Crux though most of us call it the Southern Cross. Fairly high up, roughly 60 degrees, so that’s three hand spans, you should be able to see that beautiful traditional cross of stars. Not everyone sees it that way.
Over in New Zealand, the Maori say it is Te Punga, a boat anchor. To the Pitjantjatjara of central Australia, it represents the footprint of a mighty eagle. To others it is the four unmarried daughters of a group elder and that’s from the Kanda people of Victoria.
I’d like to tell you a story that’s been documented by Katie Langloh Parker in 1896. We use this because the stories were passed on with the knowledge they’d recorded and shared. It was done in a very sensitive and respectful way so we’re quite happy to share these stories.
This story comes from the Murri people of Northern New South Wales or South-Eastern Queensland and it goes along the lines like this.
There was a time when the Great Spirit Baiame walked upon the earth and he made three people, two men and one woman. He told them what animals and plants they could eat and which ones they could not eat. Above all, they were told they could not eat the kangaroo rat. Everything was fine and dandy for quite some time, but then a terrible drought came.
Things started to die off and food wasn’t so easy to find. They were getting hungry. One man and the woman came across a kangaroo rat and they killed it and started to eat it. They offered some to the other man, but he said “No, I can’t eat that. Baiame told me not to eat the kangaroo rat.” He walked off and left them.
The man and woman that remained behind continued to eat, but then they felt, “Gee, we should go after our friend.” They walked off after him, but they couldn’t catch up. They could see him walking out over the pebbly ground and over the hills. They saw him eventually by a big coolabah plain, next to a river. He kept walking. They called out to him, but he kept walking.
And then, he dropped dead by a big gum tree. There was a crack of thunder and the spirit, the Yowie appeared. The man and the woman dropped to the ground in fear, they wouldn’t get any closer. The Yowie lifted the man’s body into the tree and then the tree started to rise up into the sky higher and higher. Two cockatoos in the tree called Mooyi in the tree flew after it and they eventually became the two pointers, Alpha and Beta Centauri that point towards the Southern Cross. But the tree higher and higher so they couldn’t see it any more but what the man and the woman could see were the eyes of the Yowie and the eyes of first man to have ever died. They got smaller as they got further away.
I love hearing stories like that from the Indigenous people of Australia. Most of us have grown up hearing stories from the North. We hear of Hercules. We go to see movies about the stories about the Titans and so on and so on. But there is now a renaissance of Indigenous sky lore in the Southern Hemisphere, the more we learn, the more we share, the better.
There you have one of stories about the Southern Cross, but there are many different stories from different communities. Please remember there is not a single Indigenous culture, there are hundreds of communities across this land and Torres Strait.
So, the Southern Cross: look carefully at it. At the moment, it’s nicely positioned. You can use it to find direction. If you draw a line, and imaginary line in the sky from the top of the cross through the bottom and multiply that by four and a half times its length, you come to what is a fairly empty part of the sky.
Well, it’s not that empty. There is a star there. Unfortunately at magnitude 5.4, that’s a way we measure star brightness – that means the majority of people simply can’t see it. If you’ve got very good eyesight away from the city when there’s no Moon, you might be able see it. It’s a star Sigma Octantis, and that’s our South star in the sky. From there, simply drop straight down to the ground and there you have south.
One of the most important uses of the stars for thousands of years has been to work out direction for navigation. If you face south then directly behind you – North. To the left where the stars come up, East. Where the stars go down to your right, west.
Look at the Southern Cross, high in the sky. Starting at the bottom with Alpha Crucis go in a clockwise direction to the next one, Beta Crucis, if you have a small telescope or pair of binoculars, centre on that star. But you need to have it on tripod to make it nice and steady. Look at that star, Beta Crucis. Right next door to it, in fact snuggled up against it, sometimes lost in the glare, is what we call DY Crucis. Now, DY Crucis is not a particularly great or interesting name. Recently, however it’s been renamed by an Australian, as Ruby Crucis. You will see this as perhaps the reddest star in the night sky. We call it a carbon star. It’s a very old star, as far as stars go. Its atmosphere is very rich in carbon. Not so much in oxygen. As a result, it takes on this ruby red appearance. It’s hard to see, but well worth a look but remember you can’t see it with the naked eye you do need a telescope or good binoculars.
If you’ve also got Beta Crucis in the centre of the eyepiece of your binoculars or telescope, scan a little bit further away and look for an object called NGC 4755. NGC, well that simply means the New General Catalogue object number 4755. Most consider the Pleiades, M45, to be the best open cluster and this to be the second best. It’s roughly a hundred stars. They’re about 6,000 light-years away, and through binoculars or a small telescope, you may even notice a few of the stars that takes on a bit of colour. Most are whitish. Some have a whitish-blue hue to them. But one of them is slightly orange-red.
To one very famous astronomer, Sir John Hershel a few hundred years ago, he looked at this and made a note in his diary, “This looks like a fine piece of jewellery laying out on velvet.” Ever since then, we’ve referred to this group of baby stars as the Jewel Box. Well worth a look. It’s pretty.
For those of you studying astronomy, open clusters like this are often used in exams because they’re pretty much the closest thing we have to a controlled environment. They’ve been formed from the same cloud of gas and dust so they have the same chemical composition. They’re about the same age and about the same distance. The only variable is that of mass, and that’s a very important one.
Remember I mentioned a moment ago one of the stars is slightly orange-red? For such a young star of around 14 million years this means it’s big and it’s dying. It will probably explode soon as a supernova. We don’t know when. It’s probably got millions but that’s about it, and then…BANG!
Snuggled up against the Southern Cross is a dark region of the sky that we commonly call the Coalsack. Some Indigenous communities look at dark patches in the sky and use those to illustrate an idea or story. Most of us look at the brighter the dots, the bright regions, but here you have a dark patch against the Milky Way that with a little bit of imagination looks like an emu.
The head with its beak is up against the Southern Cross. Its long neck passes back through Centaurus towards Scorpius where you’ll be able to see the body of an emu which is quite chunky. You might need a picture to see it fully but there are plenty of them available on the Internet. Once you’ve seen it, you’ll never miss it again.
If you live in the Sydney region, trek north about 25 kilometres from Sydney to the Ku-ring-gai Chase National Park. Look for the Elvina Track. It’s only a few hundred-metre walk from convenient parking spot and you’ll be able to see an Indigenous carving in the rock of an emu. Theories are developing that this emu in the rock is actually matching the emu in the sky that I mentioned.
If you do go there and have a look at it, please, please, treat it with respect. Don’t touch it. Sure, photograph it. Share it. Enjoy it, but look after it, as it’s a national treasure in my opinion. It’s been there a long time, and we want it to be there for a lot longer still. The emu in the sky. It’s well worth looking for.
Going back to the sky and towards the Southern Cross you’ll be able to see the famous Pointers, Alpha and Beta Centauri. They are the two brightest stars in the constellation of Chiron the Centaur, who was a very kind old teacher. In fact he was the teacher, according to some legends, of Hercules, Jason and Achilles.
But the two bright stars that just I’ve mentioned represent his front feet. Seeing the body of the centaur is pretty tough, so you’ll need a good imagination or a perhaps a star chart to see that one.
Alpha Centauri is the closest star to us after the Sun at 4.3 light years away. Through a good pair of binoculars or small telescope, you’ll actually see that it’s two stars. The two stars are locked together in a gravitational dance that takes them 80 years to go around each other once.
Quite close by, still in the constellation of Centaurus, we have perhaps one of the finest objects in the night sky that I think you can see.
It’s just visible to the naked eye under ideal conditions, but through any optical aid, you’ll be able to see NGC 5139, or Omega Centauri. It was discovered by Edmund Halley in 1677. It’s roughly a million stars grouped together in what we call a globular cluster. Much, much better than M4 that I mentioned earlier in Scorpius a little bit earlier. It’s about 16,000 light years away. The stars are so close together that if you were in the cluster, the average separation that you would be able to see is 0.1 of a light year, but in our region of the Milky Way, the stars on average are about 4 light years from one another.
It’s a very densely packed region of the sky. And only recently some ideas have come about that this in fact the core of an old galaxy that is now merging with our galaxy, the Milky Way. Omega Centauri is one of the finest objects you can see through a telescope, but again, you need to get away from the polluted skies and preferably when there’s no Moon. If you feel like a challenge, quite close by is yet another very interesting object only visible through, this time I’d have to say a good telescope, and that is NGC 5128.
It was discovered by John Dunlop in 1826 from Parramatta, where the old government observatory used to be. This is, we think, two galaxies in collision. It’s about 15 million light years away, and it has a central black hole something like 55 million times the mass of the Sun.
It’s enormously big, enormously powerful, pumping out huge amounts of radio energy. It’s well worth a look through the telescope, you can see it. It’s a little bit of a smudge.
Through a bigger telescope, believe it or not, it looks a bit like a hamburger. From high in the South, where we’re looking at the moment, around the constellation of the Southern Cross and Centaurus, I want you to turn toward your right, so we’re heading towards the Southwest.
We’re looking into what used to be the largest of all the constellations, Argo Navis, the ship that carried Jason and the Argonauts in search of the Golden Fleece. Yet another one of these stories from the Northern Hemisphere.
That constellation was deemed too big, so astronomers broke it up into smaller groups or constellations. Carina the keel, Vela the sails, Puppis the deck, Pyxis the compass. The whole region is absolutely perfect for viewing with binoculars or small telescope.
There are so many things that we can see as we go along this part of the sky. Move from the Southern Cross, and just below it and to your right a little bit, you may be able to see a faint group of stars that makes up a long skinny cross. That’s what we call an asterism, or a false constellation.
That’s a group of stars that we often refer to as the Diamond Cross and yet again you may need the map to help. Just above the Diamond Cross scan for the Carina Nebula. It’s only just visible to the naked eye under good conditions. It’s a cloud of hydrogen and helium, the two most abundant elements in the Universe. What you’re looking at is the birthplace of stars and soon, the death of at least one. This cloud of gas and dust is being bathed in ultraviolet radiation from young hot stars within it, and they’re effectively lighting it up. Within the heart of this cloud, there is a star called Eta Carinae. Eta Carinae is what we call a cataclysmic variable star. It’s a star at the end of its life. In the 1840s, it started to brighten. By 1843, it got so bright, it was the second brightest star in the night sky, and the Boorong clan from Victoria that I’ve mentioned noticed it too. They named it Collowgullouric War, meaning the wife of War, the second brightest star in the night sky, which is Canopus in the constellation of Carina the keel and I’ll get to that in a moment.
This star is dying. We’re seeing it in its final death throes. In 1843, it shed something like 30 times the mass of the Sun. That matter is now obscuring the star, making it harder to see. But shortly, very shortly indeed, it can do one thing… (pop) explode as a type 2 supernova. Look, it’s not going to happen today, but it might. It might happen tomorrow, a thousand years or a million years, but if you’re a betting person and you want to bet on the most likely star to explode during your lifetime, this is it.
By the way, don’t worry about it. It can’t possibly hurt us. It’s way too far away. Collowgullouric War, or Eta Carinae, is simply a beautiful object to look at, from this distance of between 7-8,000light years.
As we go around towards the South-West, getting low, about 30 degrees or 1 outstretched hand and one fist above the South-Western horizon we have the second brightest star in the night sky, Canopus, it is the brightest in the constellation of Carina the keel. It’s 310 light years away, 9 times the mass of the Sun, and 71 times its diameter, so it’s a very big. Canopus, or War to the Boorong of Victoria is the brother of Sirius, or Warepil the brightest star in the night sky and if you look a little further to the West you should see how far it has dropped since the start of our tour.
Special events for the month of June 2015. Let’s start with the Moon.
Wednesday 3 June will be the Full Moon at 2:19am
Wednesday 10 June will be Last quarter at 1:42am
Wednesday 17 June is the New Moon at 12:05am and that’s the best time to see the stars from a dark location obviously away from the city
Wednesday 24 June is the First quarter at 9:02pm
The Winter solstice occurs in the constellation of Taurus at 2:38 on Monday the 22nd of June. The winter solstice is when the Sun has reached it most Southerly point in its yearly cycle as we see it move across the sky, and will now start to head back towards the equator and toward the Northern Hemisphere.
In the evening sky you’ll be able to see Venus in the Northwest just after sunset. It will be very bright at magnitude -4 making it the brightest object in the night sky other than the Moon. During June it will wander through three constellations starting in Gemini for two days then moving into Cancer before ending the month in Leo. On the 20th the Moon will be close by along with Jupiter making this the best event for the month. By the end of the month Venus and Jupiter will be about ½ degree apart, the two planets will look like piercing eyes in the sky.
Jupiter starts off the month in Cancer and moves through into Leo by the second week. On 21 June the moon is directly above it. Jupiter is a great test for binoculars. A good pair should be able to see the four Galilean moons of Io, Europa, Ganymede and Callisto.
Saturn with its yellowing hues is in the constellation of Libra between the reasonably bright stars of Zubeneschemali and the orange-ish red Antares. The gibbous Moon will slide past Saturn on the 1st, the 28th and the 29th.
For the early risers, the planet Mercury very low in the East in the constellation of Taurus by the second week of June. On the morning of 15th June the thin crescent Moon is close by and on the 24th of June Mercury passes close to Aldebaran the brightest star in Taurus. Aldebaran is one of the four Royal Stars that marked the Northern hemisphere spring or Vernal equinox many thousands of years ago but no longer.
I hope you’ve enjoyed this tour of what’s visible in the Southern sky for the month of June 2015. I know it’s been a long trek but there’s just so much up there to see. You can find our monthly sky guide podcast on iTunes.
If you want more detailed sky maps about sunrise and sunset, Moon and tide information, why not purchase a copy of our book, the ‘Australasian Sky Guide’ by Dr Nick Lomb, available from Sydney Observatory or the Powerhouse Museum shop, and our website.
It’s only $16.95 if you come into us to get it. There is an additional charge for postage and handling if you do it online. Our website is Museum of Applied Arts and Sciences then follow the link to Sydney Observatory.
Our web page has a galaxy of information about astronomy and visiting Sydney Observatory to see through our telescopes, to visit our 3D space theatre and the spectacular Sydney Planetarium.
We have programs available for all ages. You can also engage with us on Facebook facebook.com/sydneyobservatory and follow our tweets on our Twitter account, @sydneyobs.
My name is Geoffrey Wyatt. I hope you’ve enjoyed this guide, and we’ll see you again, soon.