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.
Hear the Audio
See The Sky Chart
We provide a March 2020 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
For those that use the Gregorian calendar, March is the third month of the year but for a long time it used to be the first. For us in the southern hemisphere it is the time of the autumn equinox meaning the hours of daylight and night are roughly equal.
Hello there, this is Geoffrey Wyatt, one of the team 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.
We will start our tour of the night sky by looking west shortly after sunset. When I say, ‘shortly after sunset’, wait for around 40 – 60 minutes and look to where the Sun went down. That will be west.
Would you agree that most tours are more enjoyable if you have some supplies? For our tour of the sky a star map is number one. You can get one from our website, or you can purchase the book, ‘The Australasian sky guide‘ by Dr Nick Lomb. A few other supplies may include a blanket to sit on, a pillow, a faint torch for the map and something to drink, perhaps a coffee, tea, or glass of wine if you’re old enough.
Most of all you will need, imagination. Imagination and mathematics are two of the tools that unlock the secrets of the Universe so that perhaps one day we will leave our home and explore…everywhere.
Let’s begin by looking to the west at an azimuth of 270 degrees east of north. If you’re looking on the horizon, the altitude is 0 degrees. Azimuth and altitude, two simple measures we use to navigate the sky.
Let me explain. East has an azimuth of 90 degrees, south an azimuth of 180 degrees, west 270 degrees and north can be either zero or 360 degrees. We don’t mind which one you use
For altitude, you’ve 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 for roughly 20 degrees.
Turn to an azimuth of 270 degrees and then a little more to your right, or toward the north. Go up roughly 30 degrees, or one out-stretched hand span and one clenched fist. Look into the setting constellation of Taurus the bull which is perhaps the oldest of all widely recognised constellations. It will be a little hard to see because it’s getting close to the horizon but search for a V-shaped group of stars that represents the head of the bull. Now look for one slightly reddish looking star called Aldebaran which is about 65 light years away.
A light year is the distance that light travels in the vacuum of space in one year which is a long way. Light travels enormously quickly at around 300,000 kilometres every second in the vacuum of space. So, multiply that by the number of seconds in a year and you end up with a lot of kilometres, around 10 trillion!
It might seem strange but it’s not a measure of time it’s a measure of 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 concept. You see the heavens above as they were, never as they are.
Aldebaran is older than the Sun at about 6.5 billion years and its 1.7 times its mass. Although it appears at the head of a V-shaped group of stars, it has nothing to do with the group called the Hyades. They are the nearest open cluster to us at just about 150 light years away. Think of these stars as, well, babies still in a stellar nursery.
Leave Aldebaran and head roughly 20 degrees up…. ooh – 20 degrees? Oh, that’s right, that’s one hand span at arm’s length for another slightly reddish orange star. This is the 9th brightest star in the night sky designated as Alpha Orionis though it is known by its more common name, 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, meaning ‘the hand of the big man’, or as we now call it Betelgeuse.
This 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 Aldebaran. It’s about 10 to 20 times the mass of the Sun which makes it a pretty big star. Recently it has faded quite dramatically by around 1 stellar magnitude or about 2.5 times which is very odd. There are several possible explanations including a massive starspot like we see on our Sun but a lot lot bigger, an intervening dust cloud or perhaps the star is contracting as a precurser to…(pop) blowing up as a Type II supernova! That would be really really cool as we haven’t seen a naked eye star blow up since the invention of the telescope more than 400 years ago.
Please don’t worry – it can’t do anything to us. It’s 660 light years away.
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 as suburbs. Just as we have suburbs to give us a general idea of location so do constellations but for the sky.
Orion is home to one of the first objects people with a telescope or a pair of binoculars should explore. Locate the object called M42, but how? Firstly, the ‘M’ simply tells us that it was part of a catalogue of objects devised by Charles Messier in 1771. 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 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. Yes – not quite as romantic as a mighty hunter, but there you have it: The Saucepan. The three equidistant stars are the base. From the base now go up one side and you’ll see another three stars off at roughly 45 degrees that make up the handle. Concentrate on the middle star of that group of three. Through a telescope or good binoculars you should notice it’s not a single point of light but a small fuzzy blob, cloud or nebula called the Great Nebula in Orion. It 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. The baby stars, known as the Trapezium, are lighting up and stripping away the rest of the nearby cloud. As with most nebula they are best seen on a moonless night preferably away from the bright lights which is unfortunately is most of the cities and towns.
From the constellation of Orion, go a little higher and look for the brightest star in the night sky. There’s no missing it and it’s called Sirius the Dog Star. At about 8.6 light years away it’s relatively close. It’s twice the mass of the Sun and quite young at roughly 300 million years old.
Historically the stars have been used to help us navigate and keep time. The ancient Egyptians used to watch Sirius and take careful note of it getting closer and closer to the setting Sun, until finally Sirius was lost in the glare 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. The Egyptians did this year after year after year and eventually worked out that on average it would return to the same point every 365 and a quarter days. They didn’t 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.
Take a moment to look at the calendar on your wall or more probably in your phone. It rules so much of what we do: birthdays, anniversaries, public holidays: hey let’s face it, who doesn’t like those? Pay days and other special events. It then took nearly 2000 years to improve on the observations of the Egyptians to get the length of the Tropical 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 Sirius.
Head to an azimuth of zero degrees, so, remember, as we said before, that’s means we’re now looking due north at an altitude of 25 degrees. 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.
Looking due north there are two relatively bright stars Castor and Pollux. They are brothers who went with Jason and the Argonauts in search of the Golden Fleece. Several other 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.
The next constellation along, however, oh my goodness, is the hardest of all Zodiacs to see. We’re going to slip right past it because frankly there’s not a lot to it either and it is Cancer the Crab.
Continue to your right to an azimuth of about 60 degrees, so roughly in the north-east, and about 30 degrees altitude. Look for the star, Regulus. It’s roughly 79 light years away, four times the mass of the Sun and about three times the diameter so it’s a pretty big star but only the 22nd brightest. 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, continue around to an azimuth of about 150 degrees, the south- east and an altitude of just 25 degrees. Sadly, 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.
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 which is simply Crux, Latin for ‘cross’.
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.
The false cross is made 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. That constellation was deemed to be too big and was broken into four smaller constellations.
From the ‘false cross’, you should be able to see, quite close by, another very bright star 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 may 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 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.
On a moonless night away from the cities and towns in March is a wonderful time of year to see the Milky Way stretching from the east-south-east high into the south from around 11pm onward. To many Australian Indigenous communities this bright part of our galaxy looks like an emu. Once you’ve found the emu in the sky you will never forget it. I urge everyone across Australia and indeed around the world to reach out to your local Indigenous community and listen to their sky lore. From my limited experience it is truly beautiful.
All the times are given in Australian Eastern Daylight Time or AEDT:
- First Quarter Moon is on Tuesday the 3rd at 6:57am
- Full Moon will be full on Tuesday the 10th at 4:48 am
- Last Quarter on Monday the 16th at 8:34 pm
- New Moon is on Tuesday the 24th at 8:28 pm
The Autumn equinox is on Friday the 20th at 2:50 pm. 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 in the south. As a result, the Sun rises almost due east, sets due west. There is roughly equal day and night but not quite.
The only planet visible in the evening sky is our sibling Venus moving from the constellations of Pisces into Aries before moving into Taurus around the end of the month. On the 28th the crescent Moon is above and to the left of Venus.
In the morning, fast moving Mercury is always hard to catch but on the 22nd the waning crescent Moon is close by, both in Aquarius.
Jupiter, Mars and Saturn are all visible in the pre-dawn eastern sky. Over the month Saturn and Jupiter change position a little but Mars moves noticeably day to day. On the 18th the waning crescent Moon is above Mars. From the 20th to the 22nd Mars passes less than 1 degree or two Moon widths from Jupiter.
On the morning of the 19th the Moon is between Saturn and Jupiter with Mars above all three and Mercury further below all four at around 10 degrees above the eastern horizon.
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 Powerhouse Museum. I do hope you’ve enjoyed this podcast for March 2020.