Skynotes December 2012

Month Highlights

Jupiter is shining brightly in the north-east at sunset. Mars is also in the evening sky, but is found setting in the west.

Mercury, Venus and Saturn can all be seen in the morning sky. But while Mercury and Venus stay low in the east, Saturn is drifting away from the horizon, following the bright star Spica.

Sunrise & Sunset Times

Moon Phases 

The Moon will be at perigee (closest to Earth) on Thursday 13th at a distance of 357,073 km.
The Moon will be at apogee (furthest from Earth) on Wednesday 26th at a distance of 406,099 km.

Let The Moon Be Your Guide

The Moon can be used as a pointer to find other objects in the sky.

• On the morning of the 6th the waning gibbous Moon is near Regulus (Leo).
• The waning crescent Moon is below Spica (Virgo) on the morning of the 10th.
• Then on the 11th, the Moon sits to the right of Saturn.
• And on the 12th, the Moon can be found between Venus and Mercury, low to the eastern horizon.
• After sunset on the 15th the waxing crescent Moon is low in the west, with Mars just above.
• On the evening of the 25th the waxing gibbous Moon sits between Pleiades (Leo) and Jupiter.
• On the 30th the Moon sits above the twin stars of Gemini – Castor and Pollux.

Planets

Mercury can be seen during the middle of the month, low in the east before sunrise. On the morning of the 12th, the thin crescent Moon sits between Venus and Mercury.

Venus continues to shine brightly as the ‘morning star’ even though it is low to the eastern horizon. On the 1st, Saturn can be found just above Venus, and later in the month, Mercury sits below Venus.

Earth experiences the Summer Solstice at 10:11pm on Friday 21st. This is when the Sun reaches its most southerly position for the year. On this day the Sun is at its highest and it is our longest day totalling 14 hours, 47 minutes.

Mars is low in the west after sunset. On the 15th, the thin crescent Moon sits just below the red planet.

Jupiter is lovely and bright in the evening sky. It can be found towards the north-east, near the triangle that marks Taurus, the bull and includes the red star Aldebaran. On the 25th, the Moon sits between Jupiter and the bright star cluster Pleiades.

Saturn can be found in the eastern sky before sunrise. Sitting above Saturn is the bright star Spica (Virgo). The crescent Moon lies to the right of Saturn on the morning of the 11th.

Meteors

The most consistent meteor shower of the year, the Geminids, occurs between the 6th to 19th. It is quite active throughout this period, with a peak on the morning of the 15th.The shower is centred near the bright star Castor, which rises in the north-east around 11pm and is visible until dawn. We can usually expect around 20 meteors per hour. This meteor shower is unique because it is associated with an asteroid called Phaethon, unlike other meteor showers that are caused by comet debris.

Stars & Constellations

The Southern Cross is now upside-down in the southern sky and the Two Pointers (Alpha and Beta Centauri) sweep just above the southern horizon. Sitting high in the south are the Large and Small Magellanic Clouds, two satellite galaxies of our own Milky Way Galaxy. These two galaxies can be seen as fuzzy patches from dark country sites. They lie close to 200,000 light years away and are slowly being drawn in towards our Galaxy.

Low in the north-west, the great square of Pegasus (the winged horse) can be seen. In dark skies and with a clear view to the northern horizon, you might just be able to see a faint fuzzy patch below Pegasus. This is the Andromeda Galaxy (M31), the most distant object visible to the unaided eye at 2 million light years away.

Orion, the hunter is back in our skies and can be seen in the north-east from sunset. For us in the south Orion appears to be standing on his head. Many people are familiar with the central stars of Orion that are commonly known as the Saucepan.

North of Orion is Taurus the bull, with the bright star Aldebaran marking the Bull’s fierce red eye. Also part of the constellation of Taurus is the cluster of stars called Pleiades or the Seven Sisters.

The two brightest stars in the night sky, Sirius (Canis Major) and Canopus (Carina), are found towards the south-east. Further south shines Achernar within the constellation of Eridanus, the river.

International Space Station

The ISS orbits the Earth every 90 minutes at an average distance of 400 km. From Earth, the ISS appears as a bright star that steadily moves across the sky. It can often be seen from Melbourne, for example at:

4:53am – 4:59am, Tuesday 18th December.

The Station will appear in the north-west, travel past Regulus and then Saturn, before disappearing in the south-east.

Predictions of when to see the ISS can be obtained from the Heavens Above website.

On This Day

2nd 1971, Mars 3 (USSR) made the first softlanding and returned the first signals from Mars.

3rd 1973, Pioneer 10 (USA) made the first flyby of Jupiter and returned the first close-up images of the planet.

4th 1978, Pioneer Venus 1 (USA) became the first spacecraft to orbit Venus.

10th 1993, the faulty optics of the Hubble Space Telescope are repaired.

13th 1920, the size of a distant star, Betelgeuse in Orion, is measured for the first time at Mt Wilson Observatory (USA).

14th 1972, the crew of Apollo 17 (USA) were the last astronauts to walk on the Moon.

15th 1970, Venera 7 (USSR) made the first softlanding and returned the first signals from Venus.

24th 1968, Apollo 8 (USA) became the first manned craft to orbit the Moon.

25th 1758, the return of Halley's Comet, predicted by Edmund Halley in 1705, is observed by Johann Palitzsch (Germany).

31st 1744, James Bradley (UK) announces his discovery of the nutation (wobbling) of the Earth.