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 Astronomy Programs Producer.
See The Sky Chart
We provide a March 2019 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 Guide
Hello there, this is Geoffrey Wyatt, one of the team here at Sydney Observatory which is part of the Museum of Applied Arts and Sciences. I’m going to talk to you about what’s visible in the sky for the month of March. Did you know that March, or Martius used to be the first month of the year according to the old Roman calendar as formulated by Romulus around 753BCE. The year had 10 months and ended with December which make sense doesn’t it? January and February were added later.
After Julius Caesar’s calendar reform in 45BCE, it slipped down a couple of notches to month number three then made a brief comeback in many places as the start of the year, but after acceptance of the Gregorian reform went back to number three.
March, named in honour of the Roman god of war, Mars. We’re going to start our tour of the night sky by looking west shortly after sunset. When I say, ‘shortly after sunset’, you do need some time for it to get dark. You might be wait 20-30 minutes or up to an hour, but look to where the Sun went down and that will be west.
What you need are some supplies 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 a few other things to keep yourself happy and comfortable as well, perhaps a blanket to sit on, a pillow, a torch and something to drink, perhaps a nice coffee, tea or even a glass of Milo or perhaps a glass of wine if you’re old enough. Most of all you will need, imagination. 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.
The Sun has gone down, we’ve waited a little while, it’s dark and let’s begin.
But before we do that we need something else and that is a regular way of finding our position. We can do it a couple of different ways. Astronomers use terms called right ascension and declination which are simply celestial equivalents of longitude and latitude but 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 and if you’re looking on the horizon, the altitude is 0 degrees.
East has an azimuth of 90, south an azimuth of 180, west as we’ve just discussed 270 degrees and north is either zero or 360 degrees. We don’t mind which one you use.
A good thing to remember is, for altitude, you’ve actually got a built-in rule. If you hold your hand at arm’s length, then stretch out a pinkie, regardless of your age or size, it measures one degree which is twice the size of the full Moon.
If you make a clenched fist at arm’s length, that’s roughly 10 degrees. And if you spread your hand to make a hand span from pinkie-tip to the tip of your thumb, that’s roughly 20 degrees.
We should be looking at an azimuth of 270 degrees to start and we’re looking into the setting constellation of Taurus the bull which is perhaps 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 6000 years. And for around 2000 years it was home to a very important point or indeed the starting position in the sky, known as the Vernal Equinox. But not any more. Things change, ever so slightly, day-by-day for some objects and year-by-year for others.
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 rising due east and setting due west, you have roughly equal night and equal day. It’s never exactly the same and I wonder if you can think why? If I tell you, we that we see the Sun as a disk not a point source does that help?
In the morning, as soon as you see the top limb of the Sun peek above the horizon, it’s daytime until the very last point at which it sets, so there’s always going to be a little more daylight than night on the equinoxes.
So, what does the Vernal Equinox actually signify and why is it so important? From an observational point of view the Sun travelling along its path called the ecliptic, simply crosses the celestial equator from the southern hemisphere back into the northern. For the northern hemisphere the days are now be longer than the night and this became the marker for the start of spring and therefore for new life.
Astronomers worked out from many years of observation that the Vernal Equinox was occurring in the part of the sky called Taurus. 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 the 1st of March. But no longer.
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? But of course – the letter A. The next constellation along, Gemini, got a B, and so on. Clearly this was a very important part of the sky.
Just for moment consider this. Have you ever played a game of ‘Whispers’ where you pass a story from one person to another then another and so on? People often make mistakes or deliberate changes and ultimately the story is very different to how it began. Now consider passing a story from one generation to the next and you can image what might happen. Well that’s exactly what’s happened to stories about the sky.
These days we have many versions floating around about Taurus and indeed all of the constellations that I’ll mention today. You have to remember that there is no absolute unless you’re talking about the modern well defined, documented recent constellations. For something as old as Taurus there are many different versions and the one I will share revolves around the king of the Greek gods, Zeus.
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. Why? He was rather fond of the King Agenor’s daughter, Europa, who used to mind a herd of cattle. As a beautiful bull Zeus mingled with the herd and somehow convinced Europa to climb upon his back. At which point he carried her off over the waves to the island of Crete. This was 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 which is the first of four Royal or Guardian Stars.
This is a very old idea dating back to Mesopotamia thousands of years ago. The astronomers of the time noted four stars that were close to the seasonal markers in the sky, the equinoxes and solstices’. Aldebaran the 14th brightest star in the night sky was the closest bright star to the point of the Vernal equinox. 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 and a light year is the distance that light travels in the vacuum of space in one year. Light travels enormously quickly at around 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, around 10 trillion in fact!
It might seem strange but it’s not a measure of time it’s a measure of distance, the distance that light can travel in one year. Nonetheless it does have time implications as Aldebaran at a distance of 65 light years means you’re seeing it now as it was 65 years ago. You’re looking back in time. I think that is rather a cool idea.
Aldebaran is older than the Sun at about 6.5 billion years and its 1.7 times its mass. I’ve mentioned now that it’s at the head of a V-shaped group of stars. Unfortunately, it has nothing to actually do with that V-shaped group of stars; it’s just between us and the group of young stars called the Hyades. They are the nearest open cluster to us at just about 150 light years away. These stars are, well, babies still in the stellar nursery.
If we leave Aldebaran, that lovely reddish-orange star. Oh, by the way when I say ‘red’ I 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 and 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.
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 hand span 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 though its actually the second brightest star in this constellation. But not many people know it by that name because it has such a spectacular common name, and that is: Betelgeuse. Yes, that’s right, there is a star called Betelgeuse. Some people pronounce it as ‘Beetlegerze’ or ‘Beetlegeese’ but they’re all 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 second brightest star, Betelgeuse.
This particular star is quite big. It’s about 1000 times the diameter of the Sun. It’s roughly 660 light years away making it about ten times further away than the star we’ve just mentioned which is Aldebaran. It’s about 10 to 20 times the mass of the Sun which makes it a pretty big star. A big star like this which is only 10 million years old is already dying and quite shortly – we don’t know when – it should die a rather spectacular death – 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, that’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 that we can easily see. We see them explode in other galaxies all the time, they go off regularly. But we haven’t seen one explode in our galaxy since Tycho’s Star in 1572 before the invention of the telescope. So, when this star does blow up….[POP] 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 worth seeing.
By the way a constellation was a picture in the sky but now they are areas with carefully drawn borders and I like to think of them like suburbs. Just as we have suburbs to give us a general idea of location so do constellations but for the sky.
If you look at your map and 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 a belt across his waist, he’s got stars for the knees and he’s holding a shield out the front and a club above his head however you need imagination. If you expect to see one of these fabulously detailed drawings that we see on old star maps, forget it. It’s not going to happen for any of the constellations. At best it’s going to be a very simple stick figure and I think for some it’s nearly impossible. Perhaps you can even join the dots and make up your own pictures. Orion, well, again, there are lots of stories about Orion and 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 who became a good friend of the Goddess of the Hunt Artemis. Her brother, Apollo was not very keen on this relationship and tricked Artemis into shooting at a speck in the ocean as a test of her skill. As it turned out it was of course Orion swimming to safety to escape the giant scorpion that Apollo created to kill him. When she discovered what she had done, she was mortified and placed his body into the sky as the stars that we see now.
Orion is one of the first objects that people with a small telescope or a pair of binoculars should look 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 objects not to look at if you’re expecting to find a comet. So, a list of fuzzy objects that you don’t waste your time looking at. They’re never going to develop a tail and look as spectacular as Comet Halley. The list has now been expanded to a total of 110 objects but the 42nd one I think is the first ones that people look at with binoculars or a telescope.
To find it, it’s relatively easy. Look for the orange-reddish star of Betelgeuse and then for us in the Southern Hemisphere go up a little bit. 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, starting with those three in a straight line, 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. What 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 to see it at its best.
And if you do that, what you’re looking at, as I’ve mentioned, the 42nd object in Messier’s catalogue, is 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.
You’re not looking the nursery of stars that I mentioned earlier but rather the maternity ward. 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. You can actually see some of them with a small telescope and we call them the Trapezium. They’re lighting up and in fact stripping away the rest of the nearby cloud. So, when you see these brand-new stars just switching on, it’s a beautiful object to look at – but there is a trick. And the trick is that you want a moonless night and, preferably, a night away from the bright lights which is unfortunately is most of the city.
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 actually quite young at roughly 300 million years old. It has a companion snuggled up against it – but you do need a very big telescope for that. So, don’t worry about trying to do it at the moment.
This is, as I’ve mentioned, the brightest star in the night sky. So, you’ll find stories about it all over the world. Locally, unfortunately we don’t have any stories at the moment from the Sydney region. However, in 1857, William Edward Stanbridge, a wealthy English pastoralist and philanthropist, recorded stories from the Boorong, part of the Wergaia language group that inhabited the region of Lake Tyrell in what is now known as north-western Victoria. The Boorong looked at this star which we call Sirius and they call it Warepil, a male eagle and he is in fact an Elder of the Nurrumbunguttia. The Nurrumbunguttia were the old spirits that once inhabited the land but went to the heavens before the first people arrived.
Do you that know the Indigenous peoples of Australia have been looking at stars and telling stories, passing them from one generation to the next longer than any other culture on the planet? I feel so privileged that I know one story and that I am able to share with you here. It makes me very proud to be Australian.
The stars are often used for calendrical purpose also. I think one of the best uses comes to us from the ancient Egyptians perhaps as long as 5000 years ago. They used to watch Sirius, the Dog Star, the brightest star in the night sky and take careful note of it getting closer and closer to the Sun as the Sun would set, until finally Sirius was lost in the glare of the Sun for about 70 days. They’d then get up early and start looking for it rising just ahead of the Sun in the east. The first day that they could see it coming up ahead of the Sun is an event called heliacal rise.
Now, the Egyptians did this year after year after year and they worked out that on average it would return to the same point every 365 and a quarter days. They didn’t actually have the concept of decimal place, so it wasn’t as though they said 365.25 but they worked out that it was 365 days for three years and then 366 for the fourth.
Apparently, they didn’t actually make use of this for one of their main calendars because they had several and it wasn’t until it was imposed upon them by Augustus Caesar that they started using it.
Take a moment to look at the calendar on your wall. It rules everything we do: birthdays, anniversaries, public holidays: hey let’s face it, who doesn’t like those? Pay days and other special events. It took nearly 2000 years to improve on 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. 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. 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 perhaps your children or grandchildren 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 simple stick figure of a dog in this region, but you will need Dr Nick’s book or a map.
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 is one hand span and roughly half a clenched fist above the northern horizon and what you’re going to look for is a zodiac constellation. ‘Zodiac’ – have I mentioned that before? Zodiac is simply the name that we give to the path or circle of animals: the constellations through which the Sun, the Moon and the planets move. All of the zodiac constellations bar one are animals. Think about it: which of the zodiacs is not a living animal? We can’t see it at this time of year but again if you wait until the June podcast, I’ll tell you the answer to that one.
We’re looking due north there are two relatively bright stars in this particular constellation and they are Castor and Pollux. They are brothers who went with Jason in search of the Golden Fleece. Several constellations relate to this indicating its importance in years gone by.
We’re going to skip these two stars in the constellation of Gemini because there’s, well, not a lot to it. With a bit of imagination, and I know I stress that, you might just be able to see two stick figures of people that look like they’re holding hands and that’s Gemini.
The next constellation along, 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 but not now because of the 26,000-year wobble known as the Precession of the Equinoxes, the northern hemisphere’s summer solstice used to be in this part of the sky.
The word ‘solstice’ comes from two Latin words. ‘Sol’, meaning ‘the Sun’ and ‘sistere’ – ‘ to stand still’. The Sun does not actually stand still, it just stops moving north just like a ball at the top of its flight stops moving up, ever so briefly, before falling back to Earth. So, the Sun stops its seasonal northward movement as we see it because of our yearly orbit, and starts to head back toward the south.
Without any north south movement in declination the Sun appears to slip sideways. Which animal that is famous for walking sideways? 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 to look at. That’s why the second of our seasonal markers, the Royal or Guardian Stars is just a little bit to your right in the next constellation not in poor old empty Cancer.
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 in altitude. So, one hand span and one clenched fist above the horizon. And you’re looking for a single bright star. This bright star is roughly 79 light years away, it’s four times the mass of the Sun and about three times the diameter of the Sun. It’s a pretty big star but only the 22nd brightest star in the night sky [Regulus].
Here’s a challenge for you scan this part of the sky and look for an upside-down question mark. If you can see that you’re well on your way to seeing the head and fiery mane of Leo, the Lion
From Leo, I want you to continue around to an azimuth of about 90 degrees that means we are looking toward the East, and I want you to find a group of stars that look like a shopping trolley. Yes, of course, there’s no such constellation. It is supposed to be Corvus the Crow and a bird that used to have the ability to talk to people. It was however a bit lazy and after one particular epic fail, the god Apollo banished Corvus along with Crater the Cup and Hydra the Snake into the sky. All three of these constellations are in the east at the moment. 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 ‘solitary one’ because there’s nothing else nearby that’s bright to look at. 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 an altitude of just 25 degrees. Look, it’s a bit low, so it’s not a good time to see it but what you’re looking at is the third brightest star in the night sky called Alpha Centauri.
Climb a little bit higher up from Alpha Centauri to about 30 degrees and you might be able to see the smallest of all 88 constellations. It is…the Southern Cross.
That’s not its official name by the way. Its official name is simply Crux, which is Latin for ‘cross’. The Southern Cross is so famous it’s on five different national flags: 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.
Go up a little bit higher from the small bright Southern Cross, you’ll be able to see a group of stars at about 60 degrees that looks like a bigger version of the cross. It’s frequently called ‘the false cross’ and it’s not actually a constellation but rather 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 not any longer. That constellation was deemed to be too big and was broken up into four 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 as it is the second brightest star in the night sky, and it’s called Canopus. Quite close by and also in the constellation of Carina with the aid of the star map you might be able to find the fairly faint star and nebula called Eta Carina. The whole area around it 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 the region. At the heart of the Eta Carina nebula, is a cataclysmic variable star. In other words, it’s a star changing its brightness in the very final stages of its death. It’s already shed a great deal of material which is now partially obscuring the star. The last time it did anything significant was 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.
Our last stop on our tour for the moment is toward the west to an azimuth of about 220 degrees and an altitude of just 20. The star you are hunting is Achernar in the constellation of Eridanus the River. It’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 it? I think it’ cool. This star spins so fast it is the least spherical star in the Milky Way. Its equatorial diameter, its bulge around the middle, is 56% greater than its diameter around the top and the bottom or, if you like, its polar diameter. We’re almost back to our starting position of an azimuth of 270 degrees but by this stage Taurus will be very low or have set completely.
HIGHLIGHTS FOR MARCH 2019
All the times are given in Australian Eastern Daylight Time or AEDT
The New Moon is on Thursday the 7th at 3:04am
First Quarter Moon is on Thursday the 14th at 9:27pm
Full Moon will be full on the equinox, Thursday the 21st at 12:43pm, and
Last Quarter on Thursday the 28th at 3:10pm
The Autumn equinox is on Thursday the 21st at 8:58am. This is the point in time when the Sun crosses the celestial equator from the south back into the northern hemisphere. Astronomically it marks the start of autumn for us southerners. As a result, the Sun rises almost due East, sets due West. There is roughly equal day and night but not quite. The 21st is also the UNESCO designated World Poetry day and to celebrate we hope to, weather permitting, conduct a live video of the Moonrise on our Facebook page and perhaps read a poem or two. Please check our Facebook page for details nearer to the 21st.
The only planet visible in the evening sky is our smaller cousin Mars in the constellation of Aires before moving into Taurus around the 20th. For the last week it will appear to be close to the beautiful cluster M45 and therefore worth a look using something as simple as binoculars.
In the morning, Venus dominates the Eastern sky all month moving through Sagittarius, Capricornus and finally into Aquarius. On the 3rd the waning crescent Moon will be close by.
On the 2nd from around 3am onward the waning crescent Moon will be also close to the reasonably faint planet Saturn with Jupiter above in Ophiuchus.
Don’t forget that you can download this podcast via our website or via iTunes. You can purchase the, ‘Australasian sky guide’ by Dr Nick Lomb which has the full year’s full details in it. It can be purchased at all good book stores, in our shop and of course online at www.maas.museum
You can get more information by visiting our website at www.maas.museum and follow the links to Sydney Observatory. You can follow us on Facebook and on Twitter @sydneyObs.
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My name is Geoffrey Wyatt part of the team here at Sydney Observatory which is part of the Museum of Applied Arts and Sciences. I do hope you’ve enjoyed this podcast for March 2019.