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Southern Sky News for 2009 October
Global astronomy event invites the world to discover our universe
A world-wide star gazing event, "Galilean Nights", will take place from 22 to 24 October, and you're invited. Amateur and professional astronomers will be sharing the night sky with the public in a celebration of the sights and telescopic views that amazed Galileo 400 years ago as he first turned his telescope to the heavens.
Four hundred years ago in Venice, on the evening of October 22, 1609, Galileo would have watched Saturn setting in the south-west, amongst the stars of Capricornus. Later in the evening, brilliant Jupiter rose in the east, amongst the stars of Taurus the Bull, above the bright constellation Orion the Hunter.
Just three months earlier, he had built his very first telescope and had demonstrated it to the government of Venice. Aiming the new telescope at the heavens revealed to him an entirely new and amazing world, never before seen by human eyes. He could see thousands of stars through his telescope that were not visible to the naked eye.
Looking up at Jupiter, he saw that the planet, which looked like a point of light to the eye, was really a small round disc, like a small golden coin. And next to it he found four tiny stars. As he studied Jupiter night after night, he noticed that these four stars were slowly moving, apparently going around and around Jupiter. Something totally unexpected was going on!
His tiny telescope couldn't show the beautiful rings of Saturn very clearly and he was puzzled by its strange appearance, observing it again and again over the years to try and figure it all out.
On the morning of October 23 the crescent Moon rose in the east, beautifully placed just above the brilliant Morning Star, the planet Venus, amongst the stars of Leo. Galileo's telescope showed that the Moon was covered in craters and he could even make out chains of mountains on the Moon. Perhaps more surprisingly, when he looked at Venus, he saw that the planet showed phases, just like the Moon did!
This year, from October 22 to 24, Jupiter will be high in the sky early evening, amongst the stars of Capricornus. The crescent Moon will be visible in the west, to the right of the curved figure of Scorpius, amongst the stars of Sagittarius. Look out for Orion the Hunter and Canis Major rising in the east later the evening.
Planet overview for October 2009
Mercury is too near the Sun to be readily observed this month; it lies in the morning sky below Venus, which may be seen low above the eastern horizon before sunrise. Saturn is also marginally visible in the morning sky, very near and below Venus.
The easiest planet to see this month is Jupiter, which shines brilliantly as the Evening Star. It lies high overhead at sunset and is the first "star" to become visible as the sky darkens at dusk.
Mars rises very late and is high in the sky before daybreak.
The Moon in October 2009
It is Full Moon on October 04. New Moon is on October 18; keep a lookout for the beautiful slim crescent Moon returning to the evening sky in the days after the 18th. To identify the most prominent lunar craters visible during this time, take a look at the Eyepics 1: The Moon resource.
On October 13 the Moon is nearest the Earth this month, and on the 26th it is at its most distant.
Anniversary!
The first astronomical observatory in the southern hemisphere was established in Cape Town, on October 20, 1820. The "Royal Observatory at the Cape of Good Hope" was officially opened on October 29. In 1970 it was amalgamated with the Radcliffe and Republic Observatories to form the South African Astronomical Observatory (SAAO).
Star gazers diary for October
Your daily guide to what's visible in, and who's meeting under, the southern skies, follows:
| Date | Things to look out for |
| 01 | Just after sunset, look for the Moon and Jupiter high in the east. Jupiter is at the moment the brightest "star" in the sky and is our Evening Star this month. |
| 02 | Look out for the large bright Moon on the eastern horizon around sunset on Friday and Saturday. |
| 04 | It is Full Moon tonight; look out for it on the horizon around sunset. |
| 05 | Just before sunrise, the Moon is low in the west, while Venus is low in the east. Mars is in the north-east above the two bright stars of Gemini. Over the next few mornings, try and spot Mercury below Venus. |
| 07 | On Wednesday and Thursday mornings, the Moon is near the Pleiades (Seven Sisters). On Wednesday evening, the Cape Centre of the ASSA meets at the SAAO (Observatory, Cape Town). Christian Hettlage will give a talk on the theory of relativity (contact 088 123 1634). |
| 10 | The Moon is midway between Aldebaran and Mars in the pre-dawn sky. The SAAO hosts an open night, which includes star gazing and a talk entitled "The physics behind astrophysics" by Kevin Govender (contact SAAO 021 447 0025). |
| 11 | It is Last Quarter Moon today; Mars is near the Moon in the morning sky on Sunday, and even closer on Monday morning. |
| 13 | In the morning sky, Mars is in line with Castor and Pollux; the crescent Moon lies to the right. Moments before sunrise, Venus may be seen very near Saturn, extremely low in the east. |
| 14 | Regulus (in Leo) is near the crescent Moon in the morning sky. The ASSA Cape Centre presents a talk by Dr Enrico Olivier (SAAO) in Cape Town. |
| 16 | "Stars to Midnight" with Jurg in Sutherland (contact 082 556 9589). Book early and dress warmly. At Kirstenbosch Gardens the ASSA Cape Centre is hosting a "Star Walk" event. Early on Friday morning, shortly before sunrise, the crescent Moon lies near Saturn and Venus: this will be a challenge to see! |
| 17 | In Sutherland, Jurg presents the second "Stars to Midnight" event. The ASSA Cape Centre holds its monthly "Dark Sky Outing" at Paardeberg (contact Richard 082 868 0534). |
| 18 | New Moon |
| 20 | The crescent Moon is visible in the west-southwest at sunset. Watch over the next few days as the crescent Moon grows and sits higher each evening. |
| 21 | Antares (in Scorpius) is very near the crescent Moon in the early evening sky. The ASSA Cape Centre presents a talk by Chris de Coning on the history of astronomy in the Cape. |
| 22 | The first evening of the global "Galilean Nights" event. Free stargazing sessions will be held at the Brackenfell Pick 'n Pay (contact Edward 083 787 0792) and on the University of Stellenbosch campus (arranged by the Star Gazers Club; contact Auke 074 100 7237). For the next few evenings, the Moon lies between Antares and Jupiter, moving closer to the giant planet each day. |
| 23 | The second "Galilean Night", with stargazing in Kleinmond and the Strand (Star Gazers Club). The ASSA Cape Centre hosts a "Star Walk" in Kirstenbosch Gardens. |
| 24 | The final "Galilean Night", with stargazing on the Braak in Stellenbosch (Star Gazers Club). In Paarl, OOG will be hosting a stargazing event at the Afrikaanse Taalmonument from 19:00 to 22:00 (contact Serena 082 729 2716). The SAAO in Cape Town hosts an open night, with star gazing and a public lecture. |
| 26 | Jupiter can be seen above the First Quarter Moon tonight. |
| 27 | Jupiter lies below-left of the Moon in the night sky. |
| 28 | The ASSA Cape Centre meets, hosting a talk by Anthony Faull. |
| 30 | The ASSA Cape Centre hosts a "Star Walk" in Kirstenbosch Gardens. For the next two mornings, Mars is near the Praesepe star cluster, a charming sight in binoculars. |
"Galilean Nights" is a Cornerstone project of the International Year of Astronomy 2009 (IYA2009). The project website is www.galileannights.org.
Happy star gazing!
/ph
Reader's comments
Posted by Mark and Carrie.
Reply by Auke on Wednesday, 2009 September 30 @11:29.
Two readers from Florida in the USA have written to ask about a very bright star visible in the early morning sky.
Mark from St. Augustine writes that he often gets to enjoy the beautiful stars when he's on night-shift. At 05:00 AM he says he sees a prominent star in the south-east that is bright and flickers a lot, from blue to red continuously.
Carrie from Jensen Beach says she saw a very bright light in the hour before sunrise on September 29th. It got brighter and rose up in the sky quite a bit before sunrise.
I'm pretty sure what Mark and Carrie are seeing is the beautiful brilliant star Sirius, the brightest star in the heavens. I've prepared a diagram, using Stellarium, showing the Florida horizon just before daybreak, facing south-east.
High in the sky sits bright Sirius, which is the alpha-star of the constellation Canis Major, the Big Dog. Above Sirius lies three prominent stars in an eye-catching straight line - this is Orion's Belt. Orion's Sword hangs around his waist so he needs a belt to keep it all in place. (By the way, the Sword is a beautiful region of sky to explore in binoculars!)
Mark mentioned the star's charming twinkling and flickering. Its flickering is more noticeable than that of the other stars because Sirius is much brighter, so changes are more obvious.
The colour-changing flickering is caused by our unstable atmosphere, and not because the star itself has the hiccups! The light from Sirius travels through space quite undisturbed for millions and millions and millions of miles until it arrives at Earth. In the last few hundred miles, however, the light encounters our turbulent atmosphere, made up of pockets of gas that swirl and tumble about. As the star's light passes through the atmosphere it gets deflected this way and that, so that by the time it reaches your eye, it's thoroughly "mixed up", which is why you see it changing colour rapidly. If the atmosphere is particularly unstable one morning, it may even appear to dance about!
It's a lot like lying on the bottom of a swimming pool and looking up at someone standing at the pool's edge: they will appear wobbly and distorted because the water deflects the light this way and that.
If you were an astronaut on the Moon, or aboard the International Space Station, you would see Sirius shining steadily with a brilliant white colour, because there is no atmosphere in the way. This disruptive effect of the atmosphere is the main reason why space-borne observatories, like the Hubble Space Telescope, manage to get such sharp images: they are so high above our planet that there is very little atmosphere in the way to distort their view.
Back to the morning's star chart, though. Lower down and in the south is another obvious star, Canopus, the second-brightest star as seen from Earth. Canopus is a very familiar sight down here in the southern hemisphere as it is one of the far-southern stars and doesn't rise very high for northern hemisphere viewers.
Over in the east for the next mornings lies the brightest "star" visible in the dawn sky: the Morning Star, actually the planet Venus. It may well be that this is what Carrie noticed (she doesn't state what direction she was looking in) since Venus is much brighter than Sirius. Four hundred years ago, Galileo used the then-newly invented telescope to observer Venus, and noticed that it goes through phases, just like our Moon does. At the moment, Venus is very near to "full" phase, although you will need at least a small telescope to see the phase clearly.
If you're out early in the morning and can find Venus, try and also spot Mercury, just below the Morning Star. This smallest of planets moves rapidly, changing position noticeably from day to day, so now is a good time to catch it.
And as an extra planetary bonus, high in the south-east, to the right of the two stars that mark Gemini the Twins, lies the Red Planet, Mars.
There is also another planet visible, with the naked eye, at this time – can anyone guess which one?
Auke
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Southern skies
- Find out about the Moon, stars, planets and constellations visible in the southern skies this month.
ASSA Symposium
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Stars to Midnight
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