March 2011 audio monthly sky guide transcript
This is a transcript of a podcast of the March 2011 night sky guide presented by Geoffrey Wyatt. Download and listen to the podcast as you gaze up at the night sky.
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 www.sydneyobservatory.com. For more information about the night sky, we also recommend that you purchase the book, ‘2011 Australian sky guide’ by Dr Nick Lomb.
For any night viewing activity, there is a simple list of equipment that you should take outside to make your viewing not only effective but also comfortable. Being March, it’s still lovely and warm, but I think you need a blanket to sit on, a pair of binoculars, a pillow, and, as I’ve already mentioned, ‘The Australian sky guide’.
You also need to be able to find your way around the night sky. Most children are familiar with ‘Never Eat Soggy Weetbix’ to help remember their cardinal directions.
Being March we’re quite lucky with the Sun setting almost due west, and it certainly is on the equinox. So if you’re facing due west for sunset, to your right will be north, to your left will be south, and directly behind will be east.
You also need to be able to measure angles because quite often astronomers talk about the position of an object in the sky as being north by north-west and 45 or 50 degrees above the horizon. So we need a little bit of practice there.
There’s a fairly easy way of doing this. When we look at something in the sky, we like to give it direction in terms of position from north and also the altitude or height above the horizon.
If you hold your clenched fist at arm’s length, for most adults, that’s about 10 degrees in size. Of course, if you’re a big fellow like me, it might be a little bit more. But on average, a clenched fist at arm’s length is about 10 degrees.
So, if something is 20 degrees above the horizon, it’ll be two clenched fists above the horizon. If you spread your fingers, the distance from your pinky to your thumb is usually about 15 degrees for the average person. A pinky held at arm’s length is about one degree or twice the size of the full Moon.
There is also something else you need for when you are trying to find your away around the night sky, and that is, of course, imagination. One thing you can do is to practise using your imagination. Have a child – a niece or a nephew, it doesn’t matter who – draw a very simple stick figure, based on dot-to-dot, then look at that, let your imagination go, and then you may be able to see some of the creatures and characters that we have in the sky.
If you’re trying to see the very elaborate drawings that we often see in star atlases, forget it, it’s not going to happen. Simple stick figures on the other hand with lots of imagination, then, no problem.
What we are going to do for March is start by looking to the west and then turn ever so slightly to the right so that we are looking about north-west. About 23 degrees, or a hand-span and a clenched fist above the horizon, look for a V-shaped group of stars with one orange-reddish star at the top of the V. This setting constellation is Taurus the Bull.
Taurus the Bull is one of the oldest constellations that we know of. As I mentioned earlier, you will need one of our star maps with you to help identify some of these patterns. But if you look at the map, you’ll see the V-shaped head of Taurus the Bull and that will help you with the rest of the constellation.
But a bull in the sky? Why is there a bull in the sky? Well, quite simple really – we’ve probably depended upon the bull as a beast of burden or as a source of food for thousands upon thousands of years, so it’s fairly understandable that a bull would find its way into the sky.
By the way, it also, for some cultures, represents the King of the ancient Roman gods, Jupiter.
You won’t be able to make out the whole bull at this time because it’s setting quite shortly after sunset, but you will be able to see the V-shaped head and then if you join the dots you’ll be able to see the long horns which, to many people, represent a sign of fertility.
Now, depending upon your age and your eyesight, you should be able to see between 1500 to 2000 stars on any clear night. By joining the dots and making these constellations, it’s much easier to find your way around.
I challenge anybody to be able to identify and remember 2000 individual pinpoints of light. So constellations are simply a memory aid.
One of the oldest star maps dates back nearly 2000 years to Claudius Ptolemy. Ptolemy devised a chart of stars made up of 48 constellations in all. We still have all of them today although we’ve broken one of them up into smaller constellations, as it was so big. We only finished doing this in 1930 when the smallest of all constellations, the Southern Cross, came into official existence. Of course, people had been calling it the Southern Cross for hundreds of years – but only did it become an official constellation in 1930.
The best way to think of constellations is as suburbs in the sky. It’ll give you a hand to find your general direction.
Now that we have found the head and horns of Taurus the Bull, go up about two clenched fists, and you’ll be able to see another fairly bright orange reddish looking star. This is one of the more interesting stars in the night sky. It’s name: Betelgeuse. Its name has changed over the years, but Betelgeuse is a dying star. It is the brightest star in the constellation of Orion the Hunter.
Betelgeuse is about 427 light years away and nearly 1000 times bigger than the Sun. That introduces two things that we need to think about quite carefully. Stars are different sizes. Some are much bigger than the Sun, and some are much smaller. The Sun, in fact, is a fairly average kind of star.
The other thing to remember is that stars are different distances away. When we are sitting on the grass and looking up at the heavens and enjoying the show, the stars look like they’re all the same distance. For a long time, people considered the stars to be holes in the celestial sphere that let in the light from heaven. We now know that each one of those stars is a big hot ball of gas, of different size, and different distances away from us. And all of them, of course, much further away than our Sun.
So, Betelgeuse at 427 light years; what does that mean? It tells us that the light from that star has been travelling to us at the speed of light for 427 years. When you look at a star, you are, in effect, looking back in time.
Orion’s brightest star, Betelgeuse, is also very big. It’s 1000 times the diameter of the Sun. Don’t forget that the Sun is also very large at about 114 times the diameter of the Earth. It really does put into perspective just how big our universe is.
Betelgeuse – this lovely orange reddish star that we are looking at – actually represents the armpit of the Hunter. Not a particularly nice way of considering such a bright and beautiful star.
According to the ancients, it represents the armpit, but these days we call it the shoulder of the giant. Now looking for a hunter or a giant in the sky can be a little difficult. But if you look at the ‘Australian sky guide’ map, you should be able to see a simple stick figure of the Hunter. Let me tell you, most Australians who look at this part of the sky don’t see a hunter, we actually see a saucepan.
Yes, the humble saucepan that lives in the kitchen has replaced the hunter, well, unofficially of course. The three base stars of the Saucepan are Orion’s Belt. They are quite famous because they lie pretty much on the celestial equator. We get a fairly good view of these stars pretty much from north and south of the equator.
If you look at the three stars that form the base of the Saucepan, depending on the time of year, it can be the right way up or upside down. From one corner, go up to the side of the Saucepan. Now, go to the other end of the line of three and go up. You’ll see another close line of three stars at an angle. This, in fact, forms the handle of the Saucepan. If you’ve got a good pair of binoculars, and you will need a tripod or rest them or wedge them against a tree, or into a fence with a pillow for stability because you just can’t hold binoculars steady enough…. If you look at this group of three stars that make up the handle, you’ll be able to see that the middle star is not quite star-like. In fact it’s cloudy, fuzzy – or nebulous. What you’re looking at is actually the birthplace of stars. This very famous group of baby stars wrapped in a cocoon of gas and dust is a nebula by the name of M42.
M42 simply means it’s the 42nd object in the catalogue devised by Charles Messier. So the M comes from his surname, and it’s the 42nd object that he catalogued. It is perhaps one of the finest things you can look at through a telescope or through a small pair of binoculars.
If you look up a little bit higher into the sky from Orion, you’ll actually see one astoundingly bright star. That star is high in the north-western sky at the moment, and it is the brightest star in the night sky – Sirius the Dog Star in the constellation of Canis Major, the Big Dog.
Sirius is quite an interesting star. Not only is it the brightest star in the night sky, but it’s one of the closest. It’s not the closest. That would be the Sun. Then there’s a few more. This star is actually 8.7 light years away. That means that when you see it tonight, the picture that you see is as it was 8.7 years ago. It’s a big, bright, hot, young star.
Sirius is a very important historical star too because long ago the Egyptians used its position in the morning sky in relation to the rising Sun to calculate the length of the year. They worked out thousands of years ago that the length of the year was 365 and a quarter days in something that we call Heliacal Rise. An incredibly important and accurate thing to have done a long time ago.
So you can see, stars are not only beautiful, but they’re useful. You may have also heard the name Sirius before. Of course, one of the ships in the First Fleet was HMS Sirius and now because of the series of the novels and movies of ‘Harry Potter’, you’ve probably heard of the character Sirius Black who can change from a human into a dog. This, of course, relates back to the idea that Sirius is the brightest star in the constellation of the Big Dog – one of the hunting dogs of Orion the Hunter.
What I want you to do now is scan to your right and towards the east. As you do this, you’ll pass the Twins of Gemini and the almost invisible constellation of Cancer the Crab. These two are fairly hard to see but what you’ll do as you come across to your right, is you’ll be able to see a group of stars that looks a little bit like an upside down question mark. It’s not perhaps the most spectacular thing to look at. But it is in fact one of the most important constellations named from the Northern Hemisphere. So, down here in the south, well, we see it the wrong way up.
The upside down question mark actually represents the chest and the fiery mane of Leo the Lion. Leo is one of the more famous of the constellations of the Zodiac or the Path of the Animals. Leo was thought to represent the lions that left the desert looking for water around about the time that the Nile River used to flood, which curiously was also the time when the Sun was in that particular constellation.
From more modern Ancient Greek times, Leo was killed by Hercules as part of his Twelve Labours and placed into the sky. As long as you can see the question mark, you are well on the way to seeing the rest of his body using the maps I’ve already discussed.
Continue to the east, or to your right, from Leo the Lion about two handspands away from the tail and one above the ground, and you’ll be able to see another group of stars that I have to say that looks a bit like a shopping trolley. What you’re looking at is Corvus the Crow. According to legend, Corvus was a fairly lazy bird in the service of the god Apollo. Eventually, Apollo lost his temper with the bird and banished him into the sky forever, along with the constellations Crater the cup, and Hydra the Snake.
So, is it a bird or a shopping trolley? I’ll leave it up to you. Have a look and see what you can make out. This raises an interesting point about constellations. In the past, they were named after great characters from legends of heroes and villains and spectacular events that people used to talk about, but they are really in effect just a memory aid.
To us in modern society, what’s going to be more appropriate to look at and see a picture of, a shopping trolley or a bird? Who knows? Perhaps in the course of time, we’ll be looking constellations known as the Mobile phone, the Laptop or the DVD. I don’t know – but I hope not. Because the old, official constellations are somewhat romantic and they’ve been around a long time already.
Once you’ve found Corvus, which is pretty much due east at this time of the year, continue around to your right. You’ll be heading down towards the south-east. Fairly low in the south-east, I think you’ll be able to see one of the most famous of all southern constellations. It’s also the smallest of all of the 88 constellations, and that is, of course, Crux, or as most of us call it, the Southern Cross.
To most of us, it looks like a traditional Christian cross, but to many people around the world it’s different things, for example, the Maori of New Zealand know it as Te Punga, meaning the Anchor. For a truly diverse view of the southern skies and the Southern Cross, you need to visit the culture of the Australian Aboriginal communities.
In Koori astronomy, it represents many different things. To the Kanda of New South Wales near the border of Victoria, it represents the four unmarried daughters of a group elder by the name of Mulululu. He actually watches over them from his vantage point of Alpha Centauri, which is the third brightest star in the night sky, and our next door neighbour, the closest star to the Sun.
To other Aboriginal communities, for example, say, of Groote Eylandt in the Northern Territory, it represents a stingray swimming along merrily but unfortunately it’s about to be attacked from the side by a shark represented by the two Pointer stars of Alpha and Beta Centauri, part of the constellation Centaurus.
Although, throughout March, the Southern Cross is on its side and slightly upside down, I’d like to point out that even though it looks like the stars are at the same distance, they’re not. The closest star of the Southern Cross is Gamma Crucis, which is 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.
If you are one of those really pedantic people that love numbers, you can actually work it out the length of a light year by calculating the number of seconds in a year and multiplying that by 300,000 kilometres every second. You’ll end up with a number which, quite frankly, is very difficult to pronounce but it works out to be about 9500 billion kilometres. That’s just one light year. So, for Beta Crucis – 525 light years away – oh goodness! That is a long, long way.
Eventually in astronomy we actually come up with another measurement of distance because even light years become too small. The larger official unit is called the parsec. That’s a bit complicated and we’ll leave that perhaps for another time.
Wrapped around the Southern Cross, although not all that easily seen at the moment, is the fairly large and famous constellation of Centaurus – half man, half horse. But, I think we need to give that constellation another month or two to get slightly higher up into the sky.
High in the south, you’ll now be able to see the second brightest star in the night sky, 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? Ah hah! As I mentioned earlier: distances. Stars are at different distances. Sirius is only 8.7 light years away whereas Canopus is a lot further at about 310 light years. So, being so far away, even though it’s much brighter in fact 20,000 times brighter than the Sun it still comes in at number two as we look at it.
Strangely, to some people around the world, particularly fisherman from the Northern Hemisphere and those from Japan when they sail from the north into the south, they see this very bright star, Canopus, pop up over the southern horizon. Such a bright and beautiful star makes them feel good. If you feel good and you are happy, you tend to live a little longer, so legend goes. The Japanese name for this star is Nagaiki meaning long life.
The part of the sky that stretches from the Southern Cross in the south-east up to Canopus high in the south is an absolutely beautiful hunting ground for anyone with a good pair of binoculars. Use them very slowly and remember that you’ve got to mount them firmly so that you don’t shake. You’ll be able to see quite a lot of interesting objects including clusters and maybe, depending upon the sky conditions, even a nebula in the constellation of Carina the Keel, where there is a very bright dying star known as Eta Carinae.
The southern Milky Way is one of the more beautiful sights to scan. And the great thing is, in the Southern Hemisphere, we get a much better view than up north.
Now that we’re finished facing south, we’re going to swing around a little bit towards the south-west. There’s another fairly bright star. It’s the tenth brightest star in the night sky and it’s called Achernar. It’s the brightest star in the constellation of Eridanus the River.
To some Aboriginal communities, Achernar along with Canopus, represent the cooking fires of the Kungara Brothers who were also seen as the large and small Magellanic clouds our nearest visible galactic neighbours. These galaxies look like small pieces of the Milky Way that have broken off and drifted away to form little islands of cloud, but they are, in fact, entirely separate galaxies to us. You really need to be away from the city lights and you might be able to see them if there’s no Moon in the sky. Once again, some legends say that these galaxies represent the Kungara Brothers – the two closest galaxies to us.
Special events for March 2011. New moon occurs on Saturday the 5th at 7.46am. First quarter on Sunday 13th at 10.45am. Full moon on Sunday 20th at 5.10am. Last quarter Saturday 26th at 11.07pm.
The autumn equinox, from the Latin, ‘equinoctium’, meaning ‘equal night’, occurs on Monday 21st at 10.21am. And this is the start of the progression towards Easter which will occur on Sunday 24th April.
In the evening sky Jupiter starts the month very low in the constellation of Pisces just after sunset but by mid month it will be lost in the glow of twilight. As we lose Jupiter, however, Saturn will be rising mid month in the eastern constellation of Virgo and on March 20th the Moon is directly above Saturn.
In the morning sky, Venus is very bright in the constellation of Sagittarius in the east but then it moves towards Capricorn and ends the month in the constellation of Aquarius. On March 1st the crescent Moon is above and to the left of the planet Venus, and on the 27th Venus passes less than one moon-width from the outermost planet, Neptune. This provides a really good opportunity for people with a reasonable powered telescope to be able to track down our most distant planet.
Don’t forget that you can download your map of the night sky at www.sydneyobservatory.com and you can purchase your copy of the ‘2011 Australian night sky guide’ by Dr Nick Lomb from all good booksellers and of course the Powerhouse shop 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 a tour of the March 2011 night sky.