March 2012 night sky guide podcast, transcript and star 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.
Geoff provides fascinating insights into the March night sky, starting with the setting constellation of Taurus the Bull. Did you know that it is probably the oldest of all the constellations – going back at least 4,000 years? He will help you find its brightest star, Aldebaran. Then his tour will take you to the constellation of Orion the Hunter, and its brightest star, Betelgeuse, which is 1000 times the size of our Sun.
Geoff also explores astronomical mythologies of Aboriginal, Greek and Arabic peoples, other constellations, and when and where to look out for Mars, Saturn, Venus and Mercury this month.
Listen to the audio, or read the transcript below for more details.
SEE THE SKY CHART
We provide an embedded sky map (below) and a March 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 March 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 March. This Sky Guide and Audio Guide are available from our website at www.sydneyobservatory.com.au. For more information about the night sky, we also recommend that you purchase your copy of ‘The 2012 Australasian sky guide’ by Dr Nick Lomb.
For any night viewing activity, there’s a fairly simple list of accessories or equipment that you should take with you outside to make your viewing not only effective but comfortable. Being March, it’s still lovely and warm, but I think you still need to have a blanket to sit on, a pair of binoculars is always a bonus, and, of course, a pillow, and, as I’ve already mentioned, you should have your copy of ‘The Australasian sky guide’.
You also need to be able to find your way around the night sky. In other words, you need to find your cardinal directions: north, east, south and west.
But you also need to be able to find elevations or altitudes – so, so many degrees above the horizon, and so on. The good thing about March is that the Sun is setting almost due west, and certainly it is on the equinox. But for most of the month, as long as you’re looking towards sunset, you’re looking west; to your right will be north, to your left will be south, and directly behind you is east.
But that’s not how astronomers typically do it. You see, we like to start facing north, and then we turn in a clockwise direction as seen from above. And we go in angles – so, from north to east, we’d say that that would have an azimuth of 90 degrees. Another 90 degrees, making a total of 180 would be south, and another 90 to 270 would be west.
It doesn’t matter which way you look at it, whether it’s just north, east, south and west, or you use the incremental angles of azimuth.
But we also need to use some angles above the horizon. And there’s a fairly easy way to do this. You see, it doesn’t matter how old you are because it’s all in proportion. How big you are – again, doesn’t matter because it’s all in proportion.
If you hold a clenched fist at arm’s length, it’s about 10 degrees of coverage. If you spread your fingers apart so that your pinkie to your thumb is about as big as you can get it, it’s about 20 degrees. And if you hold your pinkie at arm’s length, that’s about one degree, or twice the size of the full Moon.
Now there’s one other thing that we’re going to rely on quite a lot when we’re doing our tour of the sky, and that is perhaps one of the most important concepts in the Universe, and that is: imagination.
Yeah, it’s true: mathematics and imagination – probably the two most powerful tools in our repertoire, if you like.
What I want you to do, before you go outside, just get a child – your daughter or your son, a niece or nephew; it doesn’t really matter – to draw a very simple dot-to-dot stick figure. And then I want you to look at that, and not just see dots and simple lines, but I want you to let your imagination go and see some vivid characters: heroes, villains, mythical creatures, dragons, whatever. We’re going to use those that you can see on your star map as a bit of a prompt for some of the typical characters that we expect to see but, of course, cannot see.
What we are going to do for March is to start looking west just after sunset, and turn ever so slightly to your right so you’re looking towards the north-west. About 23 degrees…. 23 degrees? Ah, that’s right, I’ve just described an easy way of doing this – so about an outstretched handspan from pinkie to thumb-tip plus a little bit more, and that will give you the general direction where we’re looking. And we’re looking at a V-shaped group of stars with one orange-reddish star at the top of the V. This is the setting constellation of Taurus the Bull.
Now, immediately, I’m sure most people will recognise that they’ve heard this name before. Taurus, we think, is perhaps the oldest of all the constellations. We certainly think it goes back at least 4,000 years – or more. And for over 2,000 years, it was actually home to something called the vernal equinox. But no longer. Ah, tricky astronomy – it changes from year to year, but ever so slightly.
Vernal equinox? It comes from a couple of different words. And we use the modern, if you like – or old, by our standards – but the Latin words ‘ver’ meaning ‘spring’ and ‘equinoctium’ meaning ‘equal night’. So the vernal equinox – and this comes from the Northern Hemisphere; we’re talking about the spring equinox. But for us in the south, of course, it’s back to front, and it’s the autumn equinox. I know it’s confusing – but, oh well, we can’t help history.
Well, what’s that got to do with Taurus? Well, thousands of years ago, when civilization started to spring up around that magnificent area between the Euphrates and the Tigris Rivers in Mesopotamia, this part of the sky was home to the vernal equinox. And people were no less skilled at observing than we are today. And they noticed this. So they said, hmm, here is a part of the sky that, with a little imagination, which may or may not have been assisted with a little red wine, looks a bit like a bull. So we’ll call it a bull. And because this is the start of spring, the start of ‘new life’, if you like, we’re going to make that, effectively, the start of our tour around the sky.
So it was considered to be, for a long time, the first of the zodiac constellations. ‘Zodiac’ is just the term that means the circle of the animals. Although, as we all know now, one of them, at least, is not an animal.
Until the time of Julius Caesar’s calendar reform, the new year actually began in March – where we can see Taurus in roughly the same position, visible low in the west just after sunset.
Indeed the significance of this particular part of the sky was no less evident by the also ancient Persian astronomers who gave letters of the alphabet to zodiac constellations. And guess which letter Taurus got? Yes, that’s right, the letter ‘A’. And then ‘B’ for Gemini, and so on, and so on.
So clearly, this was somewhat universally regarded as the starting point.
Now some of the stories – well, some of those have been lost. And they’re a little confusing. But the story that most of us are familiar with is actually from the more modern – but nonetheless, ancient, Greeks. Where Taurus represents the king of the gods, Zeus, in the form of a bull. Yes, you see, he could change his shape into whatever he wanted to be. Fair enough – he was, after all, king of everything.
And he fell in love with, or perhaps was smitten by the beauty of the daughter of Agenor. I’m not sure if I’ve pronounced his name correctly. But anyway Agenor had a daughter and her name was Europa.
So what Zeus did was he changed himself into a beautiful white bull and mingled with the herd of cattle. And he was able to coax Europa into climbing onto his back at which point he carried her over the seas to the island of Crete.
And such a famous story this is, that, ultimately, the land that we now call Europe took her name. So Taurus is, indeed, a worthy starting point for our tour of the night sky.
The other thing to remember about Taurus is that bulls are beasts of burden, so these rather odd stories that we hear may have simply been based in practical purposes. Cattle were incredibly useful then as they are now. So why not name a part of the sky after one of the most versatile and useful creatures that we have. But basically all you’re going to see is a V-shape.
So look for that orange bright star in Taurus, called Aldebaran. Aldebaran, by the way, is what has been dubbed one of the four royal stars…. And it’s a very ancient idea, again, dating back thousands of years, to the time of the Babylonians. And they had four key stars. They’re the brightest stars near the significant events in the sky which are the two equinoxes and the two solstices.
So, starting off here with the vernal equinox, the nearest bright star is Aldebaran. And it therefore became the first of the four royal stars.
But, really, look for the orange star at the head of a V-shaped group of stars, and you’ll be able to make out the head and then the long horns that make up Taurus the bull. It’s really hard to see anything more than that. But if you have your map, and you can see that, you’re well on the way.
Oh, by the way, depending on your eyesight, you should be able to see from a very dark, clear location, maybe 2,000 stars on a clear night. It’s really difficult to say to someone, ‘Look, can you please remember the positions and the brightnesses of all 2,000 stars.’
So, as I hinted at earlier, what people have done for a long time is make up some simple dot-to-dot diagrams – stick figures in the sky – and by remembering those; it’s kind of like a signpost. It helps you find your way around and you can ignore the insignificant ones and just use the brighter ones.
Now, we’re not really sure who started doing this. But, certainly, in terms of western science that we now seem to follow so closely, most of the ideas that we have have come to us from Mesopotamia. There are some newer ones. But most of them date back a long time to that wonderful region.
Perhaps the first person to put together a catalogue of these simple stick figures, or constellations, in the sky, the Roman citizen of Egypt nearly 2,000 years ago – Claudius Ptolemy.
He devised a chart made up of 48 constellations. Now, we still have all of them today, but we’ve broken one of them up into smaller constellations because it was simply too big.
People have been adding to this in a somewhat ad hoc way, and it was only completely finalised with borders, if you like, in 1930, when the smallest of all the constellations, the Southern Cross, officially came into existence.
Now, it had been around, obviously, for a long, long time, as an idea of a cross in the sky. In particular, since European sailors started venturing into the south in the 1500s and they saw a symbol that looked a bit like a Christian cross. But until then it was officially part of the much larger Centaurus.
So, 1930, everything’s been mapped out, and we now have 88 areas of the sky that cover all stars. And I think the easiest way to remember these constellations is they’re just like suburbs in the sky.
Anyway, so we’ve been having a look at the constellation of Taurus, and the first of the four royal stars, Aldebaran.
What I’d like you to do at this particular time is to go up one open handspan – so that’s about 20 degrees – and you’ll actually come across another fairly bright orange reddish star. This is one of the more interesting red stars in the night sky, primarily because of its rather unusual name.
Its name has changed over the years, and there’s lots of argument about it, including lots of historical argument about it. But these days we typically call this star Betelgeuse. It’s also the brightest star, so it’s called Alpha Orionis, in the constellation of Orion the Hunter. This is a young, but very large, dying star.
Throughout these podcasts, you’ll hear myself and some of our other astronomers give you all sorts of different numbers: distances to stars, sizes of stars, brightness, and so on. The thing to remember is that these are not absolute.
We have incredible spacecraft that have given us all sorts of spectacular, accurate measurements these days – but there is still some debate on a lot of these distances. So please – what we give is what we think is the best idea at the moment but that can change pretty much any time.
So, at the moment, we’re looking high up into the north-west, or maybe slightly north by north-west and we’re looking for this very bright orange reddish looking star…. Oh, when we say ‘red’, we don’t mean traffic light red either. It’s more of a golden orangey colour. And that is the star, Betelgeuse.
It’s about 650 light years away and about1000 times the size of the Sun. So it’s extremely big.
You see, what you’ve got is a fairly young star that’s coming towards the end of its life. It’s fairly massive. Around about 10 to 20 times the size of the Sun. And yet relatively young at less than 10 million years.
Hold on: 10 to 20 times the mass of the Sun. Less than 10 million years, already very large and red. Yes, the star is dying.
And when it does eventually die we’re reasonably sure, though we can’t guarantee it, that it will explode [makes popping sound] as a Type II supernova.
Here’s hoping that happens soon because it would be rather spectacular to see such a large nearby star explode. But again, we can’t be sure about this.
You see, some stars are bigger, some stars are smaller, some are close, some are far away. The view that you and I get is rather two-dimensional. We have no idea just by looking at them how big the star is, how bright it is, or how far away it is. So it can be rather confusing, especially when we start measuring the distances.
Betelgeuse – 650 light years away. About, as I say, somewhere between 1,000 and 1,100 times the diameter of the Sun. Don’t forget – to put that into perspective, just remember that the Sun is about 114 times the diameter of the Earth. So, goodness gracious me, that is one seriously big star.
The name itself – Betelgeuse. I know most of us have heard something like that in relation to a children’s cartoon or indeed an old, rather strange movie. But, you see, it’s a mispronunciation that’s been handed to us throughout the years through the Dark Ages to the Middle Ages to the Renaissance. We’ve basically picked up an interpretation of the Arabic pronunciation. It was something like [sounds like] ‘Ibt al Jauzah’. It’s a very difficult name to pronounce. It’s been abused, if you like, or devolved and changed, and we now call it, as I’ve mentioned, Betelgeuse [pronounced ‘Beetlejuice’].
But we believe it comes from an old Arabic name meaning ‘the hand of al Jauzah’, meaning ‘the big man’ or ‘the giant’. But, strangely, it’s been interpreted as ‘the armpit of the giant’.
And I think this is falling out of favour in terms of astronomical circles. But we still find printed reference in older books that this star actually means ‘armpit of the giant’. Ee-ew – not a particularly nice name is it? Nonetheless, if you’ve found it, you’re well on your way to finding one of the more famous objects in the sky and that’s a group of stars that Australians typically look at and refer to as ‘the saucepan’, but everywhere else around the world, it’s referred to as Orion the Hunter. Some people have actually argued that Orion was, well, somewhat of a dimwit in the sky. You see, it’s been suggested that he’s quite dim because if he’s a mighty hunter, he’s pretty much standing on a timid little rabbit called Lepus the Hare.
And he’s chasing the Pleiades, which are often shown to represent a flock of doves. So what sort of mighty hunter steps on a hare and chases doves? Well – one who’s pretty dumb.
And that’s been a suggestion that’s been around. Although, correspondingly, there’s lots of ideas that he was in fact the mightiest of all the hunters with a slight attitude problem. That boasted at one particular time that he could kill any animal on the planet.
Well, the ancient Greeks believed that the Mother of the Earth, Gaia, was not particularly happy about this idea or this boast, so she sent the giant scorpion, Scorpius, to attack and kill him. Which it did.
Other legends say that, well, Orion was so good at hunting that he would be hanging around with the goddess of the Hunt, Artemis.
Artemis’s brother, Apollo, was not so keen on his godly sister going out with a mere mortal. So he is the one who created the giant scorpion to attack and kill Orion, the Hunter.
Whichever story it was, and there are different versions of this, ultimately what happened was that the body of Orion was placed into the sky as was that of the scorpion – but on directly opposite position. So that the two can never come together and fight again. They keep an eye on each other. As one sets, the other rises.
Looking into Orion, it’s fairly easy to see three stars in a row – very nicely placed, that make a perfectly straight line. These stars traditionally represent the belt of Orion, from which hangs his mighty sword.
But for us in the Southern Hemisphere, the belt and the sword identify, if you like, Australians, Kiwis and South Africans because the three of us typically refer to that patch of stars as being a saucepan. Yes, that’s right, no longer a mighty hunter but a saucepan that you can find in the kitchen.
What I want you to do is to look at the handle of the saucepan, and if you have a pair of binoculars – now, this is quite tricky – you need to either put them onto a tripod or wedge them against the side of a building using a pillow for a bit of support – you may be able to see that the middle star-like object of that handle is not a single star but, rather, a little cloud. And the ancient word for ‘cloud’ is ‘nebula’.
So what you’re looking at is, in fact, the birthplace of stars. It’s called M42 or the great nebula in Orion. And time and time again you’ll find astronomers give things fairly, well, dim, classification names. M42 simply means it’s the 42nd object in the catalogue developed by a man whose name began with ‘M’ – and that was the Frenchman, Charles Messier.
This is truly a spectacular object if you have a small telescope or even a small pair of binoculars – as long as you can mount them and hold them still, this is a beautiful object to look at. It will look like a slightly wispy, greyish-greenish cloud of gas and dust.
Once you’ve found Orion by tracing the position of Betelgeuse, the dying red star, the saucepan – the handle with the Nebula M42, look a little bit higher and almost overhead, and you’ll see the brightest star in the night sky called Sirius the Dog Star And it is, in fact, perhaps, one of the most important stars of them all – obviously, apart from the Sun.
Not only is it the brightest star in the night sky, it’s also one of the closest. Now there are about seven which are indeed closer. But this is a lovely combination of being close and bright. It’s only twice the mass of the Sun but 25 times brighter. And at 8.6 light years away, that makes it the perfect combination for this brilliant dazzling star that we can see.
Ooh – a light year – I’ve mentioned that now twice. A light year is simply the distance light can travel in one year in the vacuum of space. Light travels enormously quickly – at 300,000 kilometres per second. So simply multiply 300,000 by 60 seconds in a minute, 60 minutes in a hour, 24 hours in a day, 365 days in a year – and that will give you the distance that light travels in one year. Goodness me – it’s a big, cumbersome number.
But what you’re looking at 8.6 light years away – our brightest star in the night sky, Sirius…. I’m sure you’ve heard that name before. Aha! Of course – it is the ship that came to Australia as part of the First Fleet, and it’s also a character in that story about a young wizard boy. Yes, you know the one. But more importantly this star was used by Egyptians thousands and thousands of years ago to work out the length of the year on average to be 365 and a quarter days in a process called Heliacal Rise.
You see they would watch the position of Sirius in relation to the morning Sun. After Sirius was lost in the glare of the Sun for around about 70 days, they would be watching for it in the morning, and that first chance that they had to see Sirius separated from the glow of the morning Sun…. the first time you do that, it’s called Heliacal Rise. And by keeping accurate records year after year after year, they were able to work out the length of the year to 365 and a quarter days.
To actually improve on that accuracy the Egyptians were able to achieve, it took another few thousand years to come up with the accurate measurements that we have today. So – rather impressive, I think.
So, stars, as I hope you’re getting to see, are not only pretty, but they’re also useful. They act as a marker in the sky. We can use them to work out time of year. We can use them to work out our cardinal directions – so, they’re beautiful and useful.
Now that we’ve had a look at Sirius, the brightest star in the night sky, what I want you to do is to drop down towards the north a little. We’re going to go past another of the zodiac constellations which, unfortunately, is not a very easy one to see. That is the twins of Gemini. This represents the youths Castor and Pollux that went on the grand adventure with Jason and the other Argonauts in search of the Golden Fleece.
But it’s not a very easy constellation to see – apart from the two brightest stars. Nonetheless, with the map and your sky guide and, again, lots of imagination, you may just be able to pick out some upside down twins holding hands.
We’re going to skip past, perhaps, the most difficult of all the zodiac constellations to see, and that is Cancer the Crab. A very faint, not so easily seen constellation, I’m afraid. But the next one over as we head towards the east is actually another very important constellation. And that is – well, let’s see if we can figure it out.
What I want you to do is to look for a relatively bright star in this portion of the sky – although we’ve got to be careful of any planets that may be there at the moment. Those pesky wanderers, or planḗtai, as they used to be called, actually confuse us somewhat.
But the brightest star in this part of the sky at the moment is the second of our four royal stars. It’s called Regulus. And it marked the position or was the brightest star near summer solstice many thousands of years ago – but, of course, no longer.
If you look at that star, what we’re going to look for now is a group of stars that from the Southern Hemisphere looks a little bit like an upside down question mark. This upside down question mark is actually the fiery mane and chest of Leo the Lion – perhaps one of the oldest and most important of the ancient zodiac constellations and, indeed, of all constellations. Leo was thought to represent at one point in time the lions that used to leave the desert looking for water around the time that the Nile would flood. You see, the Nile used to flood on a very regular basis and the Egyptians were quite skilled at using the positions of the stars to work out when this was due to happen. They also got to learn, of course, by patterns year after year that lions would be looking for water and slow-moving other animals to eat at this time. So the position of Leo was actually quite important.
From the more modern – but again, ancient Greeks, Leo was the famous constellation that was killed by Hercules as part of his Twelve Labours and eventually put into the sky. But the main thing is as long as you can see an upside down question mark, you are well on the way to being able to see Leo.
Continue towards the east, or, as we’ve been going so far , towards your right, and about one open handspan away, you’ll be able to see the constellation – well, it’s a little hard to see – but there’s not much bright around it – Corvus the Crow.
You know what? When I look at this group of stars I don’t see anything that looks like a crow at all. I can’t help but see, as we’re now looking towards the east, a group of stars that looks, well, like a shopping trolley. Mmmm.
According to the ancients, however, Corvus was bird, and it was a bird that had the ability to talk to humans. But after one particularly unsuccessful mission it was sent on by the god, Apollo, who lost his temper, he changed its colour to make it black as we see today, and took away its ability to speak. So it was banished into the sky along with the constellations of Crater the Cup and Hydra the Snake.
But look at it now – so we’re looking almost due east – you might just be able to pick out the brightest star underneath in the constellation of Virgo, called Spica. But Corvus looks like a shopping trolley.
Look, I hope it doesn’t ever become popular nature to call it a shopping trolley. These constellations have been around for thousands of years.
But this raises an interesting point. They were named after things that were important or common in the time of the people that saw them. Just as now we have our mobile smartphones, our tablet computers, our cars and airplanes and things like that. But hopefully we’ll stick to the older pictures in the sky.
As we leave Corvus in the east, we’re going around to the right again, and we’re heading towards the south-east. Reasonably low, but making its way higher up into the sky, you’ll find the smallest of all 88 constellations. Some would argue it’s the most beautiful. Some would argue it’s the most famous. Certainly in the Southern Hemisphere we’re somewhat biased. After all, it’s on our flag here in Australia.
We’re looking at the group of stars now know as the Southern Cross. This group of stars is small and bright. It has three of the top thirty bright stars in the night sky, and it now makes up the smallest area in the sky after the 1930 break-up of the sky by the International Astronomical Union.
Across the ditch, our cousins in New Zealand refer to this group of stars as Te Punga, the Boat Anchor. But to the various Indigenous communities across this land, the Southern Cross has an incredible diversity of stories and meanings. For example, our curator at the Powerhouse Museum, James Wilson-Miller, has told us of the story that comes from the Murri people up towards the top of New South Wales and in the bottom of south-east Queensland. And it relates around, well, the first person to ever die.
You see, this story of the Southern Cross tells us that long, long ago, there was a great sky spirit called Baiame who walked the Earth and he made three people, two men and one woman. And when he saw that they were alive, he gave them an idea; he told them what they could eat and what they couldn’t eat, and he said that they had to stick to that. He then left for his home in the sky. And for a long time everything went swimmingly well.
But then came a big dry spell and nearly all the plants and all the animals died out. They were so hungry that one of the men killed a small kangaroo rat, cooked it, and gave some of it to the woman and she ate it.
They offered some to the other man – but he refused because he knew what Baiame had told them about the things you can and can’t eat. He got so upset, he started to walk away.
The man and the woman that were eating stayed where they were, and continued to eat. And then they thought they’d better go and look for their companion. So they followed him off. And they walked for a long, long time. Over the sandy hills and the pebbly ground, until they found him on the edge of a coolibah plain near the side of a great river.
He was so weak from hunger but he wouldn’t have eaten the kangaroo rat. He kept walking. He kept walking and walking until he came to the side of a big gum tree, and he fell to the ground, dead.
As the man and woman approached, they yelled out to him. But they saw the huge black figure with fiery eyes right next to him. In fact, it lifted up the dead man’s body and dropped it into the hollow of a big tree.
There was then a large crack of thunder and they fell to the ground, startled and stunned. When they looked up, they saw the black figure lifting the tree up towards the sky. They couldn’t see their friend any more. All they could see were the fiery eyes of the yowie spirit carrying the tree up into the sky.
There was also a very loud screech of some Mooyi– some cockatoos that were flying after the tree, and they called out after the tree as it went higher and higher into the sky.
At last, the tree planted itself near the edge of the Milky Way, where all the other spirits live in the sky. And it disappeared from sight. All they could see now were the four fiery eyes shining out: the two eyes of the yowie spirit of death that had carried him into the sky, and the two eyes of the man who died. In fact, he was the first man to die.
The Mooyi or cockatoos are chasing after the tree in the sky, and trying to get back to the tree. And they are, of course, Alpha and Beta Centauri, the two bright Pointers that we see pointing towards the Southern Cross.
If we wait a few hours, the Southern Cross, which is presently quite low in the south-east, it’ll rotate around because throughout the night and throughout the seasons, it does a full rotation of 360 degrees. So in a few more hours from now it’ll be nice and highly placed and upright, looking more like a traditional Christian cross. And I think you’ll be able to see the eyes of the yowie and that poor man who was the first person to die.
When you look at the Southern Cross, as I mentioned earlier on, you will see that the stars are different brightnesses. But they all look like they’re the same distance – but they’re not. You see the closest star to the Southern Cross is Gamma Crucis. And that’s the one at the top of the cross as we’re looking at it in the traditional form, if you like. And that’s about 88 light years away, whereas, the second brightest star, Beta Crucis, is about 525 light years away. Don’t forget – a light year is simply the distance that light travels in one year.
Wrapped around the Southern Cross, although not all that easily seen at the moment, is the fairly large constellation of Centaurus – half man, half horse. But, I think it would be best at this particular stage to leave Centaurus for another month or two until it gets slightly higher up in the south and the south-east.
High in the south, you’ll be able to see the second brightest star in the night sky, and that is Canopus. Canopus is significantly naturally brighter than the brightest star I mentioned earlier: Sirius the Dog Star. So, how come it’s only the second brightest star? Ah hah! As I mentioned earlier: the distances. Stars are at different distances. Sirius is only 8.6 light years away whereas Canopus is a lot further at about 310 light years away. It’s also very, very bright. In fact 20,000 times brighter than the Sun. Even though it’s a lot brighter, the extra distance means we only see it as the second brightest star in the night sky.
As you go from the Southern Cross high towards Canopus, you’re actually entering a part of the sky that used to be referred to as Argo Navis, the ship that carried Jason and the Argonauts in search of the Golden Fleece.
This is a particularly intriguing story. You see, more constellations I think relate back to this story than any other. The constellation was deemed to be too big, however, and has been broken up into four smaller constellations: Carina the Keel, Puppis the Deck, Pyxis the Compass and Vela the Sails.
This whole area from the Southern Cross to Canopus is truly gorgeous. Position your binoculars so that you’ve got a nice steady view, whether you do that by resting your elbows on a pillow or you put your binoculars onto a tripod – it doesn’t really matter.
But scan this part of the sky because there is so much to be seen. You’ve got, of course, the very dense bright part of the Milky Way, the river in the sky. But you also have some clusters, some open clusters which are young stars formed at the same time. And you also have a rather intriguing cataclysmic variable star. Egads! What’s a cataclysmic variable star? A star that changes its brightness over a regular period of time.
This particular star, Eta Carina, is dying. It is indeed a young star. It’s already coming to the end of its life. The intriguing thing is that the Boorong Indigenous people who are part of the Wergaia language group in the north-west of Victoria observe this star brighten dramatically from a fairly ordinary 3rd or 4th magnitude star in the 1830s or 1840s to become the second brightest star in the night sky by 1843 and then fade from brightness by the end of the decade.
Now what these people did was absolutely amazing. They incorporated this variable star into their sky lore, and they named the star Eta, Carina, Collowgullouric War Collowgullouric War is the wife of War, which, most of us, as I mentioned a moment ago, know by its more common name of Canopus.
So this is a very good example of how indigenous peoples from around the world observe what happens in their environment and incorporate that into their sky lore.
Now that we’ve finished facing south, what we’re going to do is swing around a little bit towards the south-west. And there’s another fairly bright star – actually the 10th brightest star in the night sky, called Achernar. And it’s the brightest star in the constellation of Eridanus the River.
Now, to some Indigenous communities, Achernar, along with Canopus, represent the cooking fires of some celestial brothers that are represented by the Large and the Small Magellanic Clouds. If you’re away from the city and there’s no Moon in the sky, they’re fairly obvious. They just look like patches of Milky Way that have, well, broken off and drifted away.
But what in fact they are, are two very close, nearby, galaxies. The Large and Small Clouds of Magellan. Completely separate galaxies to us which the Milky Way is currently in the process of, well, there’s no way of being politically correct or nice about it – cannibalising.
That’s right. We’re the local bully on the block, and we’re drawing these two smaller satellite galaxies towards us, and in the next few hundred million years or so, they will actually be disrupted, if you like, and become part of our own galaxy.
Cool, huh? Don’t worry about it. When galaxies merge, there’s quite often, probably, no stellar collisions. Stars aren’t going to go banging into each other and causing the end of days, or anything like that. Galaxies pass through each other all the time. And where it does have a fairly disruptive effect on them, the stars don’t actually bang into each other.
After looking at the Clouds of Magellan, especially if you’re in a lovely and dark location, as we head back around towards the west, we’re pretty much back towards where we started. Taurus is now even further down in the north-west as is Orion and Sirius, so we’ve been looking at the stars for quite some time.
Highlights for the month of March 2012. The first quarter Moon will be on Thursday 1st March at 12.21pm. Full Moon will be on Thursday 8th at 8.39pm. Last quarter will be on Thursday 15th at 12.25pm. New Moon will be on Friday 23rd at 1.37am. And first quarter, the second one for the month, will be on Saturday 31st March at 6.41am.
The autumn equinox for us in the Southern Hemisphere will be on Tuesday 20th at 4.14pm. But don’t forget that, traditionally, people in the Northern Hemisphere will have been calling this the vernal or spring equinox.
Mars is rising in the east, in the constellation of Leo by mid-month, and will have a magnitude, or a brightness, if you like, of about minus 1.7. This is just a little fainter than the brightest star in the night sky, Sirius the Dog Star. So it’s still relatively bright and well worth a look.
Mars will be at opposition on 4th March, but it won’t be at its closest approach until 6th when it will be 100,780,000 kilometres away. That’s not too bad – but it’s a far cry from the favourable opposition which basically means a very nice alignment with us in the middle and the Sun on one side and the planet on the other side, as it was in 2003 when Mars was only 55,000,000 or so kilometres away from us. So well worth a look but not as good as it was in the past.
Looking towards the west, Jupiter and Venus make a very brilliant sight shortly after sunset, and from the 11th to the 16th, they’ll be nice and close together – technically at their closest on the 14th of the month.
On 26th, the crescent Moon will be between the two – don’t miss it! It’s a fabulous opportunity to see two bright objects, with the Moon looking west, shortly after sunset on the 26th. By the 27th, the Moon will have moved and be a little bit above and to the side of Venus.
Going back towards the east, by the end of the month, Saturn will be rising in the constellation of Virgo, just under its brightest star which is Spica the Ear of Wheat.
There’s not a whole lot happening in the morning sky. But we will get to see Mercury low in the east moving into the constellation of Pisces later in the month.
On the 11th, leading up to sunrise, the gibbous Moon will be fairly close to the bright star, Spica – about two degrees from it anyway. And also, therefore, relatively close to the planet, Saturn.
Now, earlier I mentioned that Venus will be very bright in the eastern sky, and this is something that you really do need to keep your eyes on over the next few months because we’re heading towards the transit of Venus.
The transit of Venus is, arguably, one of the most significant scientific events in Australia’s young history. It was, after all, the prime reason that James Cook left Plymouth in England in 1768 to sail south to King George’s Island – now Tahiti – to view the 1769 transit of Venus. A transit if simply when the planet Venus moves between us and the Sun.
So, in effect, what you get to see is, as that famous singer, Sting, once said: “a little black spot on the Sun today”.
That will occur on 6th June. It is a very significant event. Sydney Observatory will be doing all sorts of events for that live on the day, and streaming online.
Don’t forget that you can download your map of the night sky at www.sydneyobservatory.com.au. Just look for the astronomy tab and the monthly sky guide section.
You can also purchase your ‘2012 Australasian night sky guide’ by Dr Nick Lomb from Sydney Observatory, the Powerhouse Museum, good booksellers and also from Powerhouse Publishing online. You can also subscribe to our Sydney Observatory monthly sky guide podcasts on iTunes.
My name’s Geoffrey Wyatt. I’m Senior Astronomy Educator here at Sydney Observatory and I hope you’ve enjoyed this tour of the March 2012 night sky.