Leonids meteor shower and Comet ISON this month!
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 Melissa Hulbert (pictured, right), Sydney Observatory Astronomy Educator.
In the November sky guide, as well as showing us where to find the constellations Pegasus, Orion and Taurus, and the star clusters, Hyades and Pleiades, Mel tells us the best times to see the bright planets Venus and Jupiter.
There are two special highlights this November with the Leonids meteor shower active for most of the month (peaking on the early morning of the 17th) and also Comet ISON – which may be the comet of the century or may be a fizzer (check our blogs for updates closer to the time). For this and more, listen to the November 2013 night sky guide audio, or read the transcript below.
SEE THE SKY CHART
We provide an embedded sky map (below) and a November 2013 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). The 2014 edition is expected to be available from November 2013.
READ THE TRANSCRIPT (after the jump)
Transcript of the November 2013 monthly sky guide audio
Hello and welcome to the night sky for November. My name is Melissa Hulbert and I’m an Astronomy Educator at Sydney Observatory.
Before we start our night sky tour, make sure you download the November sky map from our website at www.sydneyobservatory.com.au. It can be found under the Astronomy tab.
Armed with your sky map and a small torch with some red cellophane covering it, find a nice dark place away from the glare of the street lights and make sure you know your cardinal directions – that’s north, south, east and west. Remember that the Sun rises in the east, moves through the northern sky during the day and sets in the west or a small compass will also point you in the right direction. Pick a comfortable spot either on a rug or a deck chair that you can lay back in. Wait about 5-10 minutes and allow your eyes to adapt to the darkness.
Look towards the north. High in the northern sky is Pegasus, the winged horse from mythology, probably with its origins in both Mesopotamian and Etruscan starlore. Pegasus was said to have been born from the blood of Medusa (the Gorgon) after she was slain by Perseus from Greek mythology.
He is also associated with poetic inspiration in Greek mythology with a fountain that was sacred to the Nine Muses which was created when he stamped his hoof on Mount Helicon. Pegasus was principally the steed of Bellerophon and in a dream Athene appeared to Bellerophon with a golden bridle and advised him to ride Pegasus. However some legends say that Perseus rode the winged horse when rescuing Andromeda.
Pegasus is easy to find, with the best-known feature of this constellation the aptly named ‘Great Square of Pegasus’. It is rather large at over 15 degrees in width and 13 degrees in height, but despite its size there are relatively few bright naked-eye stars within the Square. Working out degrees in the sky is quite easy. Hold your arm out towards the sky and make a fist. From one side of your fist to the other, this is 10 degrees. Hold your other arm out and spread your hand out as wide as you comfortably can (so the opposite of a fist), from your little finger to your thumb is 20 degrees. Put your hands side-by-side and you now have 30 degrees. This does work for everyone, as your arm length is proportional to your hand size.
Four stars outline the Square and in the past all four were a part of the constellation, however delta Pegasi is now known as Alpha Andromedae. This star was also known as Sirrah meaning ‘navel’ and marked the navel of the horse. Pegasus is the right way up for us, so we see the neck and head of the horse stretching towards the west and what appears to be his back legs towards the north-east. One interesting object is M15 or NGC 7078, a magnitude 6 globular cluster, easily visible in binoculars and small telescopes. Medium to large apertures will resolve some of the outer regions of this cluster and a dense core. M15 lies about 33,000 light years away.
Remember I mentioned the horse’s rear legs earlier? Let’s go back to those. The legs are part of the constellation Andromeda, the daughter of Queen Cassiopeia in Greek mythology. If you are away from city lights then look carefully at this area of the sky. You might see an elongated fuzzy patch of light with your unaided eye. This is the Andromeda Galaxy and is the most distant object visible to the unaided eye, lying about 2.4 million light years from us, though recent data from the Hipparcos satellite has suggested that this distance might be closer to 3 million light years. While a fascinating sight with just your eyes, if you have binoculars or a small telescope then a most amazing sight awaits you – the dark dust lanes of the spiral arms, a bright core, and if you are lucky you might pick up one or both of its companion galaxies.
To the east and slightly south of Pegasus is Cetus, the fourth largest constellation in the sky. Cetus has been depicted as a variety of animals but is generally depicted as a sea-monster or dragon-fish but some refer to it as merely a great whale.
Cetus is one of the most ancient constellations in the sky as it was Ptolemy who originally assigned 22 stars to this constellation. It contains a jewel box of coloured stars for both telescope and binocular users alike.
South of Cetus you will see the brilliant star Achernar, which means ‘the river’s end’ as it marks the end of the river, Eridanus.
Follow Eridanus towards the east and there rising in the sky is our familiar signpost of summer skies – Orion, the Hunter. In Greek mythology Orion was a hunter of great skill and boasted that he could kill all living animals. Gaea the Earth goddess was alarmed by his statement and fearing for all the animals on Earth she sent a scorpion to kill him. Orion was stung on the shoulder but was revived and placed in the stars along with the scorpion. This entire myth is played out in the stars each year. As Scorpius the Scorpion rises in the east, Orion sets in the west, defeated. When Scorpius sets in the west the healer Ophiuchus crushes the Scorpion into the Earth and revives Orion so he can rise in the east again. Orion appears in many cultures, even the ancient Egyptians saw Orion as Osiris, god of the underworld and of regeneration.
If you’re having difficultly picking out the Hunter then look for the Saucepan. This is a familiar group of stars for those of us in the Southern Hemisphere and is Orion’s belt and sword. Orion is on his side as he rises above the eastern horizon.
The middle point of light in the handle of the Saucepan (or the sword) is the famous Orion Nebula or M42. It is one of late spring’s most magnificent sights and will keep observers using binoculars or a telescope enthralled as you follow the swirls and loops of gas and dust in this active stellar nursery. Stars are forming out of the gas in this nebula which stretches about 20 light years in diameter and is 1,500 light years away.
To the south of ‘the Saucepan’ you should see the red supergiant star Betelgeuse, which is 500 times larger than our own star, the Sun. Or, if we were to place Betelgeuse where our Sun is, at the centre of our Solar System, then the edge of the star would be near Jupiter’s orbit. Betelgeuse is the shoulder or armpit of Orion and is about 427 light years away. To the north of ‘the Saucepan’ and diagonally opposite Betelgeuse is a brilliant white star, Rigel, one of Orion’s knees. Rigel is a blue-white supergiant star that shines 60,000 times brighter than our own Sun. Rigel also has a small companion star which is best seen through a telescope though if seeing conditions are not the best, small telescopes will struggle to see the companion through the glare of Rigel.
Let’s return to the belt of Orion and follow its line to the west where we come to the back of a sideways ‘V’. This ‘V’ is the head of Taurus the bull and appears to be charging at Orion. Like Cetus, Taurus is one of the most ancient constellations in our skies and like Orion is also steeped in Greek mythology. It is said to represent the bull Zeus changed into to carry Princess Europa off to Crete.
Back to the ‘V’ which is part of a large open star cluster visible in binoculars called the Hyades. One of Taurus’ eyes is an orange giant star called Aldebaran which means ‘the follower’. It follows the Pleiades, a wonderful open star cluster that can be seen with your eyes to the north west of the ’V’. The Pleiades are known as the seven sisters as seven stars are readily seen with your eyes, but away from city lights, up to 13 can be seen with the unaided eye. The whole cluster contains about 100 stars and binoculars are the best way to view this marvelous object.
Another of Messier’s objects, M1 is also in Taurus. M1 is best seen in telescopes and is known as the Crab Nebula, but is in fact the remnant of a star that exploded as a supernova on July 4 1054AD. How can we be so precise with this date?
Chinese astronomers kept very accurate records of the night sky and recorded the position of a ‘new star’ on their star maps on this date, the exact position in which we now find the Crab Nebula. Although the Crab Nebula is 7,000 light years away, the supernova was brighter than the planet Venus for weeks before it faded from view after almost two years. Even today, the nebula is still expanding at a rate of more than 5 million kilometres per hour. It emits radiation in all wavelengths from gamma rays to x-rays, UV, optical and infrared radiation and radio waves. It is exceptionally bright for a supernova remnant. The reason for this is its central pulsar energizes it.
Careful studies of the Crab Nebula revealed a pulsar near the centre, which emitted at a rate of 30 pulses per second. Additional observations have shown that the pulse rate is slowing down. During the next 1,000 years the pulse rate will fall to half its present value.
Time to turn and look towards the south. Can you see our familiar signpost of the Southern Cross and Pointers? Look low, close to the south horizon and there they are. In late spring these constellations are low in our evening skies but by early morning, they are rising again to the positions we are familiar with.
However, in their place are two cloud-like objects, a large one and a small one (you will need to be away from city lights to see them). These are the Magellanic Clouds, named after the explorer Ferdinand Magellan. They are the two satellite galaxies of our own Milky Way. The larger of the two is in the constellation Dorado, the goldfish. In 1987, the Large Magellanic Cloud (LMC) was the site of the first supernova, visible to the unaided eye since 1604 (which was observed by the astronomer Johannes Kepler). This supernova was named Supernova 1987A.
The Small Magellanic Cloud (SMC) is in the constellation Tucana the Toucan. Sitting just beside the cloud is 47 Tuc or NGC 104 a fine globular cluster, second only to Omega Centauri. It is a fuzzy object which at 4th magnitude can be easily seen with the unaided eye, away from city lights. In ancient times it was thought to be a star and given a stellar designation. 47 Tuc has the same apparent size as the Moon and has a tightly packed core. Telescopes with apertures of 100mm or greater are required to even begin to resolve this globular. It is 16,000 light years away, making it one of the closest globulars to Earth.
So what else can we look forward to seeing in the sky in November 2013?
This month after sunset, look towards the west and there is the bright evening star. Of course it’s not really a star but the name given to the closest planet to us: Venus.
It moves from Ophiuchus to Sagittarius at the beginning of the month, passing within 2 degrees of the Galactic Centre on the 2nd. On the 6th, the 3-day old waxing crescent Moon is below Venus and slightly to the north (right). On the 7th, the Moon will be slightly above and to the north (right).
Jupiter, the largest planet in our solar system is rising around 11pm mid-month in the north-eastern sky. On the 21st and 22nd the waning gibbous Moon pays Jupiter a visit. On the 21st, the Moon is above and to the north (left) of Jupiter and on the 22nd it’s beside Jupiter to the east (right).
November also has something in store for all of you early-birds! Mars is in the eastern pre-dawn sky and on the 28th, the 24-day old waning crescent Moon is above and to the east (right) of the red planet.
Mercury will be visible from the middle of the month but remains very close to the horizon and will be hard to see without good seeing conditions, and a clear view to the east horizon.
I do have one wildcard for you all this month which is the Leonids meteor shower. This shower is linked to the periodic comet 55P/Tempel-Tuttle and is usually at its best about every 33 years when the comet returns. When comets pass close to the Sun they leave a trail of small particles and dust behind. When the Earth passes through this trail we see lots of meteors appearing to come from one area of the sky. This is called the radiant and each shower is named after the constellation or bright star near which the radiant appears. In this case it’s the constellation Leo and the radiant is within the sickle or head of the lion. The best time to observe any meteor shower is after midnight, usually a few hours before dawn. The Leonids are active from the 6th to the 30th of November, with the peak on the morning of the 17th. Activity can vary from year to year and if the shower does turn out to be active this year it is certainly worth hopping out of bed for!
I’ve saved the best event for observers for last! In November, an icy, dusty visitor to our Solar System could put on a spectacular show. Comet ISON C/2012 S1 is so far predicted to be very bright, with some touting it as potentially the comet of the century. At the time of recording this monthly guide it is a little early to tell but it is looking good to be a bright comet in our skies. The comet’s perihelion (or closest approach to the Sun), will be a mere 1.2 million kilometres on 29 November and it is possible this close encounter may cause the comet to disintegrate. Best time for Southern Hemisphere observers to catch a glimpse is from mid to late November in the morning sky before sunrise. If the comet does brighten dramatically as it approaches the Sun then it may be possible to see during the daylight, a rare sight indeed! This would be around the date of perihelion, the 29th.
Make sure you check Sydney Observatory’s blog, Facebook page and tweets around this time for the latest information.
I leave you now with a quote from comet hunter David Levy “I had watched a dozen comets…slowly creep across the sky as each one signed its sweeping flourish in the guest book of the Sun.”
Will comet ISON disintegrate as it approaches the Sun? Will it be fabulous or a fizzer? Stay tuned to find out.
If you have enjoyed this podcast and think you might want to regularly check out what’s in the night sky, why not purchase a copy of Sydney Observatory’s book the ‘Australasian Sky Guide’. It not only contains detailed monthly sky guides, but is packed with astronomical information including rise and set times for the Sun, Moon and planets, tides and a detailed look at our Solar System and upcoming astronomical events. It can be purchased from Sydney Observatory and Powerhouse Museum shops or online.
You can also subscribe for free to our Sydney Observatory monthly sky guide podcasts through iTunes.
This has been Melissa Hulbert from Sydney Observatory with the November monthly sky guide podcast.