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 Dr Nick Lomb (pictured at right), Sydney Observatory’s Curator of Astronomy.
Nick takes us on a tour of the stars and constellations prominent in the January sky, including Betelgeuse and Rigel in Orion, Aldebaran in Taurus, and Sirius, the brightest star in the night sky, in the constellation Canis Major. He also tells us which planets are visible in the evening and morning sky in January. Among these is the bright planet Jupiter which is visible in the night sky throughout the month in the north-east sky. On 15th January, the Moon is above and to the right, or east, of the planet. (The Sydney Observatory January school holiday program has night programs featuring viewings of Jupiter.)
For this and more, listen to the January 2014 night sky guide audio, or read the transcript below.
SEE THE SKY CHART
We provide an embedded sky map (below) and a January 2014 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 2014 Australasian sky guide’ by Dr Nick Lomb has more information and star maps for months from December 2013 until December 2014 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 January 2014 monthly sky guide audio
Welcome to the Sky Guide for January. My name is Nick Lomb. I’m the curator of astronomy here at Sydney Observatory. This sky guide can be found on www.sydneyobservatory.com.au and then you will need to go to the ‘astronomy’ tab, which is on the far right of the web page. We’ll start off the sky guide by touring the stars visible this month. In the second part of this podcast, we’ll consider planets and other special events like eclipses and the position of the planets happening this month.
Before starting the tour of the night sky, if possible, download the star map that’s available from this website. It is available each month. Then take it outside. Make sure you know the cardinal directions: north, south, east and west.
And ideally, you should have a torch with a red light, so you can have a torch with a red light by putting a bit of red cellophane in front of an ordinary torch, or you could obtain a red LED torch from an astronomy supply shop. The idea of the red torch is you can look at the stars without wrecking your adaptation to the night sky. So you can look at the star map and look up at the sky and see both.
Let us start our tour of the night sky, and start off by facing north in the late evening. And, of course, in January, it does not become dark until fairly late, at least in most states of Australia. So settle down and look towards the northern sky.
Dominating the north sky is the familiar constellation of Orion. This is always a welcome signpost for the Australian summer sky. It’s quite an unmistakable constellation. It’s high up in the northern sky, almost due north in the evening, and it can be recognised as it has four stars in a rectangle and three stars in a row in the middle. These three stars in a row are Orion’s Belt.
The star on the lower right of the rectangle is a reddish star, one of the few stars in the sky that you can actually recognise its colour. The star called Betelgeuse, a giant star, hundreds of times wider than our own Sun. The name Betelgeuse comes from Arabic. It means the armpit of the giant. So although it sounds like a very exotic name, in fact it means something very mundane. It describes the location of the star in an old fashion drawing of the constellation.
You may ask why Orion’s armpit is at the bottom of the constellation and not at the top. The reason is the constellation was named in the northern hemisphere and we’re looking at it from the southern hemisphere. So poor Orion has his head down and his legs above his head, not I would imagine, a comfortable position.
The star diagonally opposite Orion is another bright star, but without Betelgeuse’s red colour. It’s a star with a bluish-white colour, a star called Rigel. This is also a very bright star, but is not anywhere near as large as Betelgeuse.
It’s a long way from us. It is 775 light years away. That is, light from this star has taken 775 years to reach us. Or we could say that the light that we see from Rigel left it back in the 1200s or the 1300s, which of course is a very long time ago.
Rigel is a star that is fairly late in its life cycle. Unlike our own Sun, which is converting hydrogen to helium, Rigel is converting helium into carbon and to oxygen. Stars use that kind of fuel only at a very late stage of their life cycle.
The star is fairly hot. It’s temperature is 11,000 degrees Celsius, very much hotter than the outer surface of our own Sun, which is around 5,500 degrees. Rigel has a distant companion as well, that is, a star circling around it, but it’s a long way away from the main star of Rigel.
One of the many nice things about looking at Orion is that it can be used as a signpost to find other stars and star groupings in the sky. Let us extend a line through the three stars of Orion’s Belt, that is the three stars in a row, towards the left. That is, towards the west, and reach another bright star, a star called Aldebaran. That is the brightest star in the constellation of Taurus the Bull.
Aldebaran is a reddish-orange star. It’s colour is not quite as obvious as that of Betelgeuse, but it’s still not the usual white colour that we can see for most stars in the sky. Aldebaran is a giant star, about 40 times as wide as our own Sun. It is shining at a brightest about 350 times that of our own Sun. It’s distance from us is 65 light years. That is, the light that we see left it 65 years ago.
Aldebaran is in a group of stars that forms an upside down V in the sky. Looking for those stars is the easiest way to find the constellation of Taurus the Bull and Aldebaran. What is interesting is that the V shaped group of stars are much further away than Aldebaran. Aldebaran is actually between us and the other stars in the group. The stars in the group are all part of one cluster called the Hyades. The stars of the Hyades are a 150 light years away from us.
The stars of this particular cluster of stars, the Hyades, are all at the same distance. They all move in the same direction in the sky. They all formed at the same time. Because of their geometric properties and the properties of the individual stars, astronomers can actually determine the age of that cluster of stars.
The age of the stars of the Hyades turns out to be 660 million years. This may sound like a long time compared to human lifetimes, but in fact it’s quite recent at least in astronomical terms. Our own Sun has an age of something around 5,000 million years. So 660 million years is relatively recent.
If we go a little bit further along the line that you’ve extended from Orion’s Belt towards the left, that is towards the west and past Aldebaran…So if we extend it a bit further we reach another compact group of stars that are called the Pleiades. The Pleiades are the most famous star cluster in the sky. This group of stars provides a very good test of eyesight. Most people can see six stars, but those with very good eyes can also see a fainter seventh star.
There are many legends and stories associated with these stars. According to Greek mythology, they are the Seven Sisters. The story is that something happened to the seventh sister and that is why it’s much fainter than the other six.
There are similar stories told by the Australian Aboriginal people. According to one group of stories, they are the seven ancestral women. One of these women fell in love with two spirit men on Earth and stayed behind, while the other six returned to the sky. The one sister and the two spirit men became the parents of everything on Earth, the originators of everything else on Earth.
Through a telescope, many more than seven stars can be seen, hundreds of stars. Photographs of the stars show that there are bits of gas and dust floating around many of the stars in the cluster. It was first thought by astronomers that these bits of gas and dust are the remnants of the gas and dust from which the cluster of stars, the Pleiades, originally formed.
However, when astronomers measured the velocities, that is, how fast the gas and dust was moving and how fast the stars were moving, they found the stars and the gas and dust were moving in a different direction. So there is no connection between the gas and dust and the stars. It seems that the stars have just bumped into this cloud of dust, and they’re moving through it.
Now let’s extend Orion’s Belt in the opposite direction. We first extended it towards the left, towards Aldebaran and further towards the Pleiades. Now let’s extend it towards the right, towards the east and upwards until we reach Sirius, the brightest star in the sky. Sirius is also the brightest star in the constellation of Canis Major, the great dog. Occasionally Sirius is referred to as the Dog Star.
It’s the brightest star in the sky, so it’s worth becoming familiar with its brightness, because if you see anything brighter than Sirius in the sky, it’s likely to be a planet like Jupiter or Venus. Venus, of course, can be the brightest object in the night sky apart from the Moon.
One of the interesting things about Sirius is that it has a companion star, a very faint companion star called by astronomers by the name Sirius B. Not an exciting name, but it’s a simple way of separating the object from the main star.
Although it does not have an exciting name, it is a very exciting object because Sirius B is very compact, exceptionally compact and also very faint. Astronomers consider that it is a white dwarf star, a star about the size of the Earth, yet at the same time the mass of the Sun. So it’s exceptionally compact and very dense.
So, for example, you could take a matchbox amount of material from Sirius B and you would not be able to lift it. It would take several cranes because its mass would be several tons. This companion star is very hard to detect because it’s overwhelmed by the brightness of the main star, Sirius A. It was first detected back in the 1840s by an astronomer called Friedrich Bessel. He noticed that there was a slight wobble in the motion of Sirius. That wobble was due to a companion star circling around the main star, Sirius A.
Sirius B was finally seen by the optician Alvan Clark in the United States in 1863. Clark was testing a new telescope that he was building, a very large telescope. He tried it out on Sirius, as it is the brightest star in the sky.
While he was trying it out, he noticed there was a faint object next to the bright star of Sirius, and that is the faint white dwarf star, Sirius B. It takes 50 years to circle around the main star. The two stars were closest together in 1994, and they’ll be furthest apart in 2019. So over the next few years, it will be easier to tell them apart, and it will be easier to see Sirius B.
Let us now go, briefly, to the southern part of the sky, so turn around and face south. The Southern Cross is in the south-east. It is on its side at this time of the year. The way to recognise the Southern Cross is that there are two Pointer stars, Alpha and Beta Centauri, directly below.
It is important to look for Alpha and Beta Centauri because the Southern Cross can be easily confused with another group of stars a little higher up in the sky which astronomers call the False Cross. The real Southern Cross is much more compact and has the two Pointer stars directly below, pointing to the stars in the Southern Cross.
Let us use the Southern Cross as a signpost and take a line from the star on the left of the cross and the top star of the cross, and take a line upwards and reach a very bright star almost overhead, a star called Canopus. That is the second brightest star in the sky, almost as bright as the star Sirius.
This completes the guide to the stars in the January night sky. We’ll continue with the second part of this podcast, talking about the planets and other phenomena and special events that are happening in the January night sky.
Now let us turn to the special events and planet positions for January 2014. On 4th January, Saturday 4th January, the Earth is closest to the Sun for the year at 10.59pm. That is an event astronomers call perihelion. It just happens that the Earth is closest to the Sun in the middle of the southern summer. It does not really cause summer but it does mean that our summers are a little bit hotter than they would be otherwise as the Earth is closer to the Sun. It also means that the Earth is moving faster at that time of the year so our summers are a little bit shorter than they would be otherwise.
There are planets to look at in the evening. At the beginning of the month we have two planets to look at, in fact, the two brightest planets in the night sky – Venus and Jupiter.
Venus is visible at the beginning of the month, low in the western sky but disappears into the twilight with the sky becoming too bright for the planet to be visible. Just before it disappears, on the 3rd January, a very thin crescent Moon will be above and to the right or north of the planet. That will be an interesting challenge to try and see Venus in the brightening twilight together with the very thin crescent Moon. So that’s worth looking out for on the evening of 3rd January.
The bright planet Jupiter is visible throughout the month in the north-east sky. On 15th January, the gibbous Moon is above and to the right, or east, of the planet.
For those people who rise early, there are planets to look at in the morning sky before dawn.
Venus, that has disappeared from the evening sky, appears low in the eastern sky just after the middle of the month. On 29th January, a thin crescent Moon will be above Venus.
The red planet, Mars, is in the north-east sky and it is below and to the left or north of the brightest star of the constellation of Virgo, the Maiden, the bright star, Spica.
On 23rd January, the gibbous Moon is above and to the left or north of Mars. On the next morning, the Moon, which is now at last quarter phase, is above and to the right, or east, of Mars.
The bright planet Jupiter which is also visible in the morning sky is visible at the beginning of the month, low in the north-west. It does disappear after the middle of the month.
The ringed planet Saturn is visible in the eastern sky. On Australia Day, 26th January, the crescent Moon is just below and to the right or south of the planet.
This completes the guide to the night sky in January 2014.
If you’d like to get more information about what’s visible in the night sky, you can purchase a copy of the ‘2014 Australasian sky guide’. This publication, which has just been released, is something that I produce each year for Sydney Observatory and the Powerhouse Museum. It is published by Powerhouse Publishing.
You can obtain it if you visit Sydney Observatory or the Powerhouse Museum, or you can buy it online
You can buy it personally from Sydney Observatory or the Powerhouse Museum, or you can buy it online from the Sydney Observatory website – www.sydneyobservatory.com.au – click the ‘Bookshop’ tab at the bottom of the page. The price is a very reasonable – I may be a little bit biased but it’s a very reasonable price of $16.95 – a bit more if you’re buying it online to cover postage and handling.
You can listen to these night sky podcasts from the Sydney Observatory website – www.sydneyobservatory.com.au – and just click on the astronomy tab at the right of the page in the top menu bar. You can also subscribe to the podcast through iTunes.
On the Sydney Observatory website you can find lots of other information. There are regular posts on the Observatory blog. There is also a self-guided walking tour app that you can purchase for $1.99 that will guide you around the grounds of Sydney Observatory, Observatory Hill, which of course overlooks the very beautiful Sydney Harbour, and then the app will guide you onto the Sydney Harbour Bridge and through the historic Sydney Rocks area.
Talking about Sydney Observatory – it is open for booked night visits. On those visits, you will see our telescope domes and see the night sky on clear nights – but certainly look at the telescopes even if it’s cloudy. And on cloudy nights there are other programs available such as the 3-D space theatre and the mini planetarium.
The Observatory is also open during the day almost every day during the year from 10am until 5pm.
During the daytime you can visit without making a booking, and it’s free. You can look around the exhibits and the grounds without charge. There are charges if you want to take part in a staff-led daytime program and, of course, these are highly worthwhile.
Information on all this is available through www.sydneyobservatory.com.au. And if you want to listen to the podcasts, click on the Astronomy tab at the right, and choose the monthly sky guides from the left-hand sidebar.
I am Nick Lomb. I am a consultant curator for Sydney Observatory, and this has been the January 2014 night sky guide podcast.