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 Education Program Producer.
If you’re not sure how to find your way around the night sky, Geoff presents some easy tips for how you can find angles above the horizon just using your fist, fingers and arm – and it doesn’t matter how old or big you are as the sizes of your fist, fingers and arms are proportional with the rest of you – so it works for everyone!
Geoff takes us on a tour of the stars and constellations prominent in the March sky, including the bright star Aldebaran in the constellation of Taurus, and the bright star Betelgeuse in the constellation of Orion.
Geoff’s fascinating talk is enriched with historical and mythological astronomical references – ranging across cultues including Indigenous Australian, Arabic and ancient Greek.
SEE THE SKY CHART
We provide an embedded sky map (below – please be patient as it can take a little while for it to load) and a March 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.
READ THE TRANSCRIPT (after the jump)
Transcript of the March 2015 monthly sky guide audio
Hello there, this is Geoffrey Wyatt, the Education Officer here at Sydney Observatory which is part of the Powerhouse Museum. I’m going to talk to you about what’s visible in the sky for the month of March which is the first month of the year according to the calendar devised by Romulus in roughly 735 BC.
First month of the year? Well, actually, not any more. After Julius Caesar’s calendar reform, it slipped down a couple of notches to month number three.
Anyway, so what we’re going to do in honour of the god of war, the planet Mars, we’re going to start our tour of the night sky by looking west shortly after sunset. Now when I say ‘shortly after sunset’, you do need time for it to get dark. So we might be waiting 20-30 minutes, depending on your latitude but up to an hour or so after, look where the Sun went down and that will be west.
What you need are some supplies with you to make this tour easier to follow. First and foremost you’ll need a map of the night sky which you can get from our website. Or you can purchase the book, ‘The Australasian sky guide’ by Dr Nick Lomb.
You’ll need some other supplies to keep yourself happy and comfortable as well, perhaps a blanket to sit on, a pillow, a torch…. Now, quite often, people like to place a little bit of red cellophane over the end of the torch to read the map or the book [which helps your eyes adapt to the dark sky], something to drink, perhaps a nice coffee, tea or even a glass of Milo. And of course, imagination. Because the more imagination you have when it comes to joining the dots and looking for these mythical creatures, the easier it will be to find your way around.
If you’re really keen, you might like to have a pair of binoculars, preferably mounted on a tripod, or even a small telescope. But you don’t have to. They’re certainly an advantage – but they’re not required for this tour.
So, the Sun has gone down, we’ve waited a little while, it’s dark. You may just pick up a hint of glow of sunset in the west and we’re about to begin.
But we need something else and that is a regular way of finding our position. Now we can do it a couple of different ways. Astronomers use terrible terms called right ascension and declination which are the celestial equivalent of latitude and longitude.
They’re a bit tricky so we’re going to use a simpler version: azimuth and altitude. Azimuth is simply a degree measured in an easterly direction from north. And altitude is a degree measured from the horizon. So if you’re looking to the western horizon, you’re looking at an azimuth of 270 degrees east of north – so, in other words, you’re looking due west – and if you’re looking on the horizon, the altitude is 0 degrees.
So east has an azimuth of 90, south an azimuth of 180, west 270 degrees and north is either zero or 360 degrees. We don’t mind which one you do.
Now, another thing to remember is, for altitude, you’ve actually got an in-built ruler. If you hold your hand at arm’s length, then stretch out a pinkie [little finger], well, from one side of the pinkie, regardless of your age [or size], and for most people this is fine, it measures one degree or twice the size of the full Moon.
If you make a clenched fist at arm’s length, that’s roughly ten degrees. And if you spread your hand to make a handspan from pinkie-tip to the tip of your thumb, that’s roughly 20 degrees.
So, we’ve done that; we’re looking west, and we’re looking into the setting constellation of Taurus the bull
to perhaps what is the oldest of all constellations. It will be a little hard to see because it’s getting close to the horizon but you’re looking for a V-shaped group of stars that represents the head of Taurus the bull. We think it may date back around about 6000 years. And for around 2000 years it was home to a very important starting point or measuring position in the sky, and that is the vernal equinox.
But not any more. Remember, this started off thousands of years ago, and things change, ever so slightly, day-by-day for some objects and year-by-year for others.
The vernal equinox. The vernal equinox? What does that mean? In Latin: ‘ver’ means ‘spring’ and ‘equinox’ comes from ‘equinoctium’ meaning ‘equal night’. So on the vernal equinox, when the Sun is setting due west, you have roughly equal night and equal day. It’s never exactly the same because we use the disk of the Sun, and the Sun’s not a point source, of course, so as it comes up over the horizon, it’s daytime, and the very last point at which it sets, so there’s always going to be a little bit more daylight than nighttime. But vernal equinox – equal night – when the Sun is rising due east and setting due west for everybody on the planet.
Now, thousands of years ago in that spectacular cradle of civilisation region, Mesopotamia, the area between the great rivers of the Euphrates and the Tigris, astronomers noticed – and they worked out by year after year of observation that the vernal equinox was occurring in this part of the sky. So, they decided to mark the beginning of spring, the start of new life, as the start of the year. And that’s why until relatively recently for some countries, the year used to begin on 1st March. But no longer, of course.
So, the year used to begin with this vernal equinox occurring in the constellation of Taurus. And to give you an idea just how important this part of the sky was, ancient Persian astronomers used to assign letters to the constellations. Guess which letter the constellation of Taurus the bull used to get? Hmmmmm? Figured it out yet? Of course – the letter A. The next constellation along, Gemini, got a B, and so on. So clearly this was a very important part of the sky.
Consider passing a story on from one generation to the next. Well, even easier than that, I’m sure everybody’s played a game of Whispers where you tell someone next to you a story, they pass it on to the next person to them, and then the next person and the next person, and by the time you’ve got through half a dozen people, the story’s completely different. Well the same sort of thing has unfortunately happened to stories in the sky.
So we have many versions floating around about Taurus and indeed all the constellations that I’ll mention today. So you have to remember that there is no absolute unless you’re talking about the modern, recently made constellations. But for something like Taurus which is thousands of years old, there are many different versions. But one particular version which I think is rather unusual and rather interesting revolves around the king of the Greek gods, Zeus.
So, Zeus could change his form into whatever he wanted. He was, after all, king of the gods. And one particular time he changed his form into that of a white bull. You see he was rather fond of the King Agenor’s daughter, Europa, who used to mind a herd of cattle. So he changed his form into a white bull, mingled with the herd and somehow or other convinced Europa to climb upon his back. At which point he carried her off over the waves to the island of Crete. Now this is such a famous story that the land mass we now refer to as Europe took her name – Europa / Europe.
When you’re looking at Taurus and this V-shaped group of stars that I’ve mentioned, look for one slightly reddish looking star called Aldebaran. Now Aldebaran is the first of what I’ll mention are the four Royal Stars or the four Guardian Stars.
This is a very old idea dating back to Mesopotamia thousands of years ago. Aldebaran was the nearest star to the vernal equinox that I’ve just mentioned. So they said, OK, well the vernal equinox – there’s nothing you can actually see happen in that part of the sky – so we’ll use a marker in the night sky. And that is the star, Aldebaran.
Now Aldebaran is the 14th brightest star in the night sky. Its old Arabic name means ‘the follower’ probably because it’s following the nearby group of stars called the Pleiades.
Aldebaran is about 65 light years away. Now a light year, remember, is the distance that light travels in the vacuum of space. Light travels enormously quickly: 300,000 kilometres every second. So multiply that by the number of seconds in a year and you end up with a lot of kilometres.
So it’s not a measure of time – because a light year is, in fact, a year – it’s a measure of distance: how far light can travel in one year. So Aldebaran is 65 light years away. We’re seeing it now as it was 65 years ago. In fact, you’re looking back in time. Rather cool thought, I always think.
This star is about 650 million years old, so it’s not very old. And it’s about 1.7 times the size of the Sun. I’ve mentioned now that it’s at the head of a V-shaped group of stars. Well unfortunately it has nothing to do with that V-shaped group of stars; it’s just between us and them.
This is a group of young stars called the Hyades and it’s actually the nearest open cluster to us at just about 150 light years away. So these stars are, in fact, babies. They’re still in the nursery. They’re very young and they’re rather nice to look at. But they are spread out compared to other open clusters but they’re also the closest one to us.
If we leave Aldebaran, that lovely reddish-orange star…. Now when we say ‘red’, by the way, we don’t mean traffic-light red; it’s not that at all. It’s more of a golden orange colour. There are very very few stars, in fact, none that I’m aware of, that are, if you like, ruby red to the naked eye. There is one very close to the Southern Cross but you’ll have to wait until I do the June podcast to hear about Ruby Crucis.
Anyway, what we’re going to do is leave Aldebaran and head roughly 20 degrees up…. ooh – 20 degrees? Oh, that’s right, that’s one handspan at arm’s length. So, head 20 degrees up and look for another slightly reddish orange star. This is the 9th brightest star in the night sky and it’s called Alpha Orionis. But not many people know it by that name because it has such a spectacular common name, and that is: Betelgeuse [pronounced ‘Beetle Juice’]. Yes, that’s right, there is a star called Betelgeuse. Some people call it [pronounced] ‘Beetlegerze’ or ‘Beetlegeese’ but they’re mispronunciations of the old Arabic name: Yad al-Jauza [pronounced Ib-tel-yarze], meaning ‘the hand of the big man’, or as we now call it, Orion’s brightest star, Betelgeuse.
Some people will say that it actually means ‘armpit of the giant’ because it’s the shoulder of the mighty hunter, Orion. There’s a little bit of debate about that and, again, with something so old, we can’t really be sure. It’s unlikely that it’s the armpit of the giant but we just don’t know.
This particular star is quite big. It’s about 1000 times the diameter of the Sun. It’s roughly 660 light years away, so much further away, in fact, ten times further away than the star we’ve just mentioned which is Aldebaran in Taurus. So 660 light years distance for Betelgeuse and roughly 10 to 20 times the mass of the Sun. That makes it a pretty big star. And a big star like this which is only 10 million years or so of age is already dying. And quite shortly – we don’t know when – it should die a rather spectacular death [makes popping sound] – as a supernova. In fact, a Type II supernova.
Please don’t worry – it can’t do anything to us. It’s 660 light years away; it’s an enormous distance. Nonetheless, we’re very excited by this and I really hope it does explode during – well, can I be selfish and say? – my lifetime. Because since the invention of the telescope we’ve not actually had a star explode in our galaxy. We see them explode in other galaxies all the time: pop, pop, pop, pop, pop. It’s incredible how often they go off in all the galaxies we see. After all, there are a lot of them. But we haven’t seen one explode in our galaxy since Tycho’s Star before the invention of the telescope. So when this star does blow up…. Soon? Who knows? It could be tomorrow. It could be in a thousand years. It could be in a million years. We just don’t know. Nothing to worry about. But, temporarily, this star will outshine all the other stars in the galaxy combined. That’s a sight worthy of seeing. But of course, let me state again, nothing to worry about.
Now, this star is the brightest star in the constellation of Orion. If you look at your map – either that you’ve printed off for free or from Nick’s ‘Australasian sky guide’, you can see Orion quite clearly labelled. Look, with a little imagination, or perhaps a lot, you may be able to make up a stick figure of a hunter. You can see the shoulders. He’s got his belt. We’ve got stars for the knees. He’s holding a shield out the front and a club above his head. But again, you need imagination. If you expect to see one of these fabulously detailed drawings that we see in old star maps, forget it. It’s not going to happen for any of the constellations. It’s going to be a very very simple stick figure. And with your imagination you have to fill in the picture. And I think most people have done this at some stage or another. And perhaps you can even join the dots and make up your own pictures. And we’ll get to one of those fairly shortly. A hunter. Orion. Well, again, there are lots of stories about Orion. And they’re different. But they may have had a common origin. We just don’t know any more.
One of the stories I like is that Orion was a mighty hunter that used to hang out with the Goddess of the Hunt, and her name was Artemis. Now Artemis’s brother, Apollo, was not very keen on this half-god, half-human, Orion, hanging out with his sister. So, through a sleight of hand, he tricked Artemis into shooting Orion with her bow and arrow. When she discovered what had happened, she was mortified and placed his body into the sky as the stars that we see now. Other stories have Orion as a bit of a thug – can I say that? – and that he boasted that he could kill any animal on the planet. Now Mother Earth was not terribly keen on this idea so she created the giant scorpion, Scorpius, to attack and ultimately kill him. But it was a rather spectacular battle between the two and after they both died, their bodies were placed in the sky for us to see as a reminder to check our egos because…. Don’t boast that you can kill any animal on the planet. You never know what will happen. But the battle, as I said, was so spectacular that Orion’s body and the scorpion were put into the sky completely separated. So you won’t see them ever together in the sky. So with Orion fairly high overhead at the moment, that means Scorpius is beneath the horizon, so you’re not going to be able to see it.
Orion, by the way, is one of the first objects that people with a small telescope or a pair of binoculars should be looking at. What I want you to do is to locate the object called M42. It is a very famous object to look at. ‘M’ simply tells us that it was part of a catalogue of objects devised by a Frenchman in 1771. His name was Charles Messier. He made up a list of 40-odd objects not to look at if you’re expecting to see a comet. So a list of fuzzy objects that – don’t waste your time looking at these; they’re never going to develop a tail and look as spectacular as Comet Halley. This list has now been expanded to a total of 110 objects. But the 42nd one I think is the first object that people with a pair of binoculars or telescope should look at.
To find it, it’s relatively easy. Look for the orange-red star Betelgeuse and then for us in the Southern Hemisphere go up a little bit more. You’ll see three stars in a row that form a lovely straight line, a nice equidistant straight line. To Australians, South Africans and our cousins across the ditch in New Zealand, we typically call this group of stars The Saucepan. Yeah – not quite as romantic as a mighty hunter, but there you have it: The Saucepan. The three stars that I’ve just mentioned are the base of the saucepan. I want you to go up one side and you’ll see another three stars off at roughly 45 degrees that make up the handle of the saucepan. Concentrate on the middle star of that group of three. It’s not a single point of light. But you will need binoculars or a small telescope.
And if you do that, what you’re looking at, as I’ve mentioned, the 42nd object in Messier’s catalogue, it’s called the Great Nebula in Orion. This is a cloud of gas and dust that’s about 1300 light years away. It’s 24 light years from side-to-side. Twenty-four light years across – that’s enormously big. And roughly 2000 times the mass of the Sun.
What you’re looking at is not the nursery of stars that I mentioned earlier but rather the maternity ward. Because when we look into this middle star-like object, we see a little part of this cloud glowing as a result of baby stars just switching on in the heart of that cloud. Now the stars – you can actually see them with a small telescope: we call them the Trapezium, and they’re lighting up and in fact stripping away the rest of the nearby cloud. So you’re seeing brand new stars just switching on. It is a beautiful object to look at – but there is a trick. And the trick is you want a moonless night and, preferably, a night away from the bright lights.
From the constellation of Orion, what I want you to do now is go a little bit higher and look for the brightest star in the night sky. There’s no missing it. It’s pretty high. It’s bright. It’s called Sirius, the Dog Star. It’s about 8.6 light years away so it’s relatively close. It’s twice the mass of the Sun and, again, it’s quite young at roughly 300 million years old.
It actually has a companion snuggled up against it – but you do need a big telescope for that. So, don’t try, you won’t be able to see it with a small telescope or a pair of binoculars.
This is, as I’ve mentioned, the brightest star in the night sky. So you’ll find stories about it all over the world. Now, locally, unfortunately we don’t have any stories from the Sydney region. However in 1857, William Edward Stanbridge, a wealthy English pastoralist and philanthropist, recorded stories from the Boorong, a group of people part of the Wergaia language group that inhabited the region of Lake Tyrell in north-western Victoria. The Boorong looked at this star which we call Sirius and they called it Warepil. Now ‘warepil’ is a male eagle. And he was chief of the Nurrumbunguttias. The Nurrumbunguttias were the old spirits that once inhabited the land but went to the heavens before the first people arrived.
So the Indigenous people of Australia have been looking at stars and telling stories and passing them from one generation to the next longer than any other people on the planet. And that is such a spectacular idea.
But there are other stories as well. And I think one of the really cool stories comes to us from the ancient Egyptians. Now again, thousands of years ago but still relatively recent times compared to the Indigenous people of Australia. But nonetheless, thousands of years ago, the Egyptians used to watch this star as it moved across the sky: Sirius, the Dog Star, the brightest star in the night sky. They would watch it setting in the west, getting closer and closer to the Sun as the Sun would set. Then they’d lose it in the glare of the Sun for about 70 days. Then they’d get up early and start looking for it just rising ahead of sunrise. And the first day that they could see it in the east, coming up ahead of the Sun is an event called heliacal rise.
The Egyptians did this year after year after year. And they worked out that on average it would return to the same position every 365 and a quarter days. They worked out therefore, several thousand years ago the average length of the year. Now they didn’t actually have the concept of decimal place, so it was not as if they said 365.25 but they worked out 365 and a quarter days averaged to 365 days and every four years you do something slightly different by adding a day on.
Now they didn’t actually make use of this for one of their main calendars because they had several of them. And it wasn’t until it was imposed upon them by Augustus Caesar that they started using that. But nonetheless, thousands of years ago they worked out on average the length of the year to 365 and a quarter days. And this is truly mind-boggling.
Take your calendar on the wall and look at it. It rules everything that we do: birthdays, anniversaries, public holidays (let’s face it, who doesn’t like those?), special events. Those little boxes on the back of the door on those calendars are so important.
Do you know what? It took nearly 2000 years to improve the observations of the Egyptians to get the length of the year correct by an additional – wait for it – 0.002% which is roughly 11 minutes. So thousands of years to work out an improvement by just 11 minutes. I take my hat off to the ancient Egyptians and their observations of the Dog Star, Sirius.
Ooh, Sirius, let me think…. Ahh, but of course, I’ve heard that name elsewhere and hopefully so have you. It was one of the ships that came to Australia as part of the First Fleet. And I do believe in more recent times it featured as a character in a series of novels about a young wizard boy. I’ll leave that to your children to tell you who that was.
Once we’ve finished with Sirius – oh, and by the way, you should be able to make out a stick figure of a dog in this region, but you’ll probably need Nick’s book or, of course, your map. So hopefully you’ve got that map with you and a red torch so it doesn’t affect your night vision and, yeah, with a bit of imagination, you should be able to see a fairly simple stick figure of a dog. Certainly a lot easier than the Small Dog located nearby with the star Procyon but, look, we’ll skip Procyon for the moment.
What I want you to do is to head to an azimuth of zero degrees, so, remember, as we said before, that’s means we’re now looking due north at about 25 degrees altitude. So that’s one handspan and roughly half a clenched fist above the northern horizon and you’re going to look for another zodiac constellation. ‘Zodiac’ – have I mentioned that before? Zodiac is simply the name that we give to the path or the circle of animals: the constellations through which the Sun, the Moon and the planets move. And all of the zodiac constellations bar one are living animals. Think about it: which zodiac is not a living animal? We can’t see it at this time of year but again if you wait for the June podcast, I’ll tell you the answer to that one.
So, looking due north there are two relatively bright stars in this particular constellation and they are Castor and Pollux. Castor and Pollux represent brothers that went with Jason in search of the Golden Fleece – which is a really spectacular story, and lots of constellations in the night sky actually relate back to that particular story. So it’s a very famous story in years gone by.
We’re going to skip Gemini because there’s not a lot to it. With a bit of imagination, again, and I know I stress that but you really do need it to see the stick figures, you will be able to see two stick figures of people that look like they’re holding hands. And that’s Gemini.
The next constellation, however, oh my goodness, it is the hardest of all zodiacs to see, so we’re going to slip right past it. And I use that word deliberately. And I’ll get back to that in just a moment.
Several thousand years ago, the summer solstice used to be in this part of the sky. Now the word ‘solstice’ comes from two Latin words. ‘Sol’, meaning ‘the Sun’ and ‘sistere’ – ‘ to stand still’. So at the summer solstice the Sun has stopped moving northwards and of course I should point out we’re talking about things as seen from the Northern Hemisphere in terms of these ancient ideas. Of course that’s where a lot of this stuff comes from.
So from the Northern Hemisphere, thousands of years ago, the summer solstice occurred in this constellation. The Sun stopped moving north in its yearly motion and started to head back south. So the Sun was not moving north or south but it was, if you like, slipping sideways – east-west.
Think of an animal that is famous for not walking forwards. Aha! I hear you say: the crab. That’s right, we’re looking into the zodiac constellation of Cancer, the Crab. The sad thing about Cancer is there’s just nothing bright there to see, which is a real bother. And that’s why, even though it’s a key point in the sky – not any more, of course, as I’ve mentioned, and I’ll keep mentioning, things change – but since there were no bright stars nearby, the second of our four Royal Stars is just a little bit to your right.
So, continue to your right to an azimuth of about 60 degrees, so roughly in the north-east, and about 30 degrees above the horizon, altitude. So, one handspan and one clenched fist above the horizon. And you’re looking for a single bright star. This star is roughly 79 light years away, four times the mass of the Sun and about three times the size of the Sun. So it’s a pretty big star. Its only the 22nd brightest star in the night sky but it’s the closest bright star to that summer solstice as seen from the Northern Hemisphere several thousand years ago. It’s the second of our four Royal Stars. The star you are looking at is Regulus in the constellation of Leo the Lion.
What I want you to do here is to look for an upside down question mark. Or some people prefer to see an old-fashioned sickle. If you can see that, you’re well on your way to seeing the head and the fiery mane of Leo the Lion.
Again, in the Southern Hemisphere for us, it’s upside down so it’s a little tricky to see. But with some imagination and patience, you should be able to see a majestic cat in the sky, sitting there with its legs out the front and a tail out the back. Poor old Leo the Lion didn’t have a nice end. He was one of the twelve labours of Hercules. So Hercules did fight poor old Leo, and he died, and the Lion was put into the sky.
Now, near the stars Theta and Iota Leonis – look there’s no nice way of saying this – we’re actually talking about the stars near his private bits, if you look at the map. You’ll actually with a pair of binoculars be able to scan the sky and you may just see a couple more of these faint fuzzy smudges that won’t become comets. That’s right – they’re more Messier objects. We’re looking at Messier 65 and Messier 66, along with another galaxy called the Leo Triplet. They’re about 35 million light years away but you will need a good pair of binoculars. More importantly, I think you’ll need to put them onto a tripod or wedge them against something to keep them nice and still.
Scan this part of the sky or mark it on the sky map that you can download, and you’ll be able to see some galaxies about 35 million light years away. From this part of the sky which is Leo, I want you to continue around to an azimuth of about 90 degrees. So we’re looking towards the east, and I want you to find the constellation of Shoppingus Trollaius. Say, what? Yes, of course, there’s no such constellation. I made it up: guilty as charged. What you’re looking at is a constellation that, to me, and to many people, now looks like a shopping trolley.
So, look towards the east, and maybe you can see a shopping trolley. However it is supposed to be Corvus the Crow. Now Corvus the Crow was a bird that used to have the ability to talk to people. But it was a bit lazy. After one particular epic fail, the god Apollo banished Corvus the Crow, Crater the Cup and Hydra the Snake into the sky. So you’ll see these constellations in the east at the moment. Corvus – yeah, I think it looks like a shopping trolley. Just slightly higher than Corvus you should be able to see the bright star Alphard, which is the brightest star in the constellation of Hydra the Snake.
Alphard is an Arabic name which means ‘the solitary one’ because there’s nothing else nearby that’s bright to look at. So look for a solitary bright star and you’ve probably found Alphard in the constellation of Hydra.
Moving on from this part of the sky, I want you to go around to an azimuth of about 150 degrees and about 25 degrees above the horizon. Look, it’s a bit low, so it’s not a good time to see it but what you’re looking for is the third brightest star in the night sky, called Alpha Centauri.
I think it is a bit too low at the moment. We’ll have to wait another month or two, I think, to see that, at its best. But climb a little bit higher up from Alpha Centauri to about 30 degrees…. I mean, yeah, that extra 5-10 degrees does make a difference. And you’ll be able to see the smallest of all 88 constellations. It is, of course, the Southern Cross.
Now that’s not its official name, by the way. It’s official name is simply Crux, which is Latin for ‘cross’. To our friends over in New Zealand, it’s known as Te Punga which means ‘the anchor’.
The Southern Cross is so famous it’s actually on five different national flags. It’s on many other province or island flags but five national flags. So, it’s us [Australia], New Zealand, Samoa, Papua New Guinea and Brazil. But there’s a bit of a trick to finding it on the Brazilian flag because there are so many other stars. They’re also back-to-front because they’re seen from outside the celestial sphere in the realm of god, from the outside, looking in.
There are many different stories about the Southern Cross. I won’t go into too many of them now because it’s best seen when it’s higher in the sky. Again, wait for the June podcast and I’ll tell you much more about it. But, very quickly, to some Indigenous communities around Australia, it looks like the footprint of an eagle. To others it is a group of unmarried daughters and to others still it represents a stingray swimming along. The thing to remember about this wonderful Indigenous culture that we have in this land: there is no single Aboriginal word or Aboriginal idea. There are hundreds of different communities and groups and many of them have vastly different stories.
Going up a little bit higher from the Southern Cross, you’ll actually see a group of stars at about 60 degrees above the horizon that confuses people, especially over summer – just as we’re moving into March as well. This particular group of stars that looks like a cross is frequently called ‘the false cross’. Now it’s not a constellation; it’s actually an asterism which simply means a group of stars that make up a picture that’s not officially a constellation. This picture is made up of stars from the constellations of Carina the Keel and Vela the Sails which used to be part of a much larger constellation – one of the original 48 as described by Claudius Ptolemaius – and that is Argo Navis; but no longer. That constellation was too big and was broken up into smaller constellations.
From the ‘false cross’, you should be able to see, quite close by, another very bright star. This star is not quite as bright as Sirius that we looked at earlier but nonetheless it’s close because it is indeed the second brightest star in the night sky, and it’s called Canopus. Again, to the Indigenous people of the Lake Tyrell area, and that’s the Boorong of the Wergaia language group, this star is called War. It’s written W-a-r – the noise made by a crow. So this star, War, is actually the brother of Warepil which was Sirius that I mentioned earlier.
Quite close by the star Canopus, and in the constellation of Carina, you’ll be able to find the star called Eta Carina. Now Eta Carina is a rather remarkable region of the sky that you should look at if you’ve got a pair of binoculars or a small telescope. Oh, by the way, the Boorong name for Eta Carina: Collowgullouric War which means ‘wife of War’.
This whole area is rather spectacular and I can’t urge you strongly enough to get out a pair of binoculars or a small telescope and simply scan this region. The region immediately around Eta Carina itself is called the Eta Carina nebula and it’s about 10,000 light years away, and it contains a cataclysmic variable star. In other words, it’s a star that’s changing its brightness but it’s in the very final stages of its death. So it’s already shed a great deal of material which is now partially obscuring the star. The last time it did anything significant was in 1843 when it went from being a fairly inconspicuous background star to the second brightest star in the night sky. And then it faded over about a ten-year period. During this time it came to the notice of the Boorong clan, and that’s why they named this star Collowgullouric War; the wife of War. But in it there is a dying star surrounded by a nebula and nearby too there are lots of wonderful things to see if you’ve got the sky map and binoculars. So, for example, we have a beautiful cluster of stars called NGC 3293. Say what? NGC? Well that just means the New General Catalogue, object number 3293. And it contains about 50 stars roughly 8000 light years away, and they’re about 10 million years old. Awwww, 10 million years old for a star. They’re so cute. They’re still very young stars as far as stars’ lifespans go.
Nearby there’s another very nice open cluster of stars – again, that means they’re a young group – NGC 3235. And that’s a beautiful group of stars to look at. But you will need the binoculars or a small telescope.
Going a bit further in this region too, you may just be able to see NGC 2070 which is called the Tarantula Nebula. It’s a cloud of gas and dust thousands of times bigger than the Orion nebula that I mentioned earlier. It’s 160,000 light years away. Look, it’s only 52 degrees in altitude at the moment. Now, for stars that’s high enough to be able to see easily. But for us, for a nebula, it’s getting a little bit low.
You need to be away from Sydney and its bright lights or, in fact, any large city, and certainly not on a moonlit night. And with the binoculars if you scan this region around Carina and into Dorado the Goldfish, you’ll be able to locate the Tarantula nebula. It’s well worth a look if you can find it.
Now our last stop on our tour at the moment, go around towards the west a little bit further, and you’re looking for another bright star called Achernar. Achernar is in the constellation of Eridanus the River. So, we’re looking at an azimuth of about 220 degrees. Now, remember the methods I gave you for finding your direction earlier? You can go back to north and use your handspan or your fist to work around the 220 degrees. Or you can just go straight to west which is 270 degrees and then two handspans and one clenched fist back to your left, and an altitude of just 20 degrees, so one handspan above the horizon, you’ll be able to see a star that’s about 140 light years away, seven times the mass of the Sun, but 3000 times brighter. It may be a little hard to see because it is relatively low – so why am I bothering with this star?
Because it’s a cool star. As far as we know it is the least spherical star in the Milky Way. Its equatorial diameter so, if you like, its bulge around the middle, is 56% greater than its diameter around the top and the bottom or, if you like, its polar diameter. Because this star is spinning so quickly, it’s bulging around the middle. It’s also interesting to look at because Achernar, along with the star I mentioned a little while ago, Canopus, to some Indigenous communities in the centre of Australia, represent cooking stars for two brothers, the Kungara brothers, that are represented by the Large and Small Magellanic Clouds, two nearby galaxies. And these cooking stars, well that’s where the bad people go to get cooked at the end of their life. Yuk! Not a particularly nice way to end but that’s where we’re going to do it. Because if we continue back towards the west where we began – so an azimuth of 270, by this stage Taurus will have completely set in the west.
And highlights for March 2015. The Full Moon will be on Friday the 6th at 4:06am; last quarter Moon on Saturday the 14th at 3:48am; New Moon on Friday the 20th at 7:36pm; and first quarter, Friday the 27th at 5:43pm.
The autumn equinox will be on Saturday the 21st at 9:45am. Now, many countries around the world use the equinox and the solstice to change the seasons. Here in Australia, of course, we do it on the first of the month. The equinox is simply one of two times each year that the Sun on the ecliptic crosses the celestial equator.
So on the 21st, the Earth’s poles are exactly the same distance from the Sun. What that effectively means is that the Sun will rise due east for everybody and set due west.
There is a total solar eclipse on Friday 20 from 7:40 to 11:50 UT. Maximum duration of totality is 2minutes 47seconds. Sadly, the eclipse is not visible from Australia.
On Friday 6th the Dawn Spacecraft will begin orbiting the large asteroid Ceres.
Jupiter dominates in the north eastern sky after sunset in the constellation of Cancer. It will be located in the north. On the 3rd, the gibbous Moon is above and to the right of Jupiter.
You can purchase the book, ‘Australasian sky guide’ by Dr Nick Lomb, which has the full year’s worth of details in it.
You can get more information by visiting our website at www.sydneyobservatory.com.au and you can follow us on FaceBook and Twitter. This is Geoffrey Wyatt, Education Program Producer at Sydney Observatory. I hope you’ve enjoyed this podcast for March 2015.