The Night Sky in December 2005
Looking at the night sky with the naked eye or using a telescope is fascinating and each month these notes keep you up-to-date with unfolding events.Maps of the current night sky can be seen by clicking HERE
Phases of the Moon
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| New Moon Thursday 1 |
First quarter Thursday 8 |
Full Moon Friday 16 |
Last quarter Friday 23 |
Click HERE to see the phase of the Moon on each day of the month.
Monthly Highlights
Well, December is finally here and we are approaching the shortest day of the year on the 21st. After that the days will start to get longer again. This is point when the Sun will be at its lowest point at midday (noon) for the whole year. With the long dark nights, we have an ideal opportunity to wrap up warm and get outside to explore the Universe with our own eyes.
December 9th - Venus reaches its brightest for 2005
© Stellarium
The planet Venus comes to the fore this month as it reaches its most brilliant for the whole of 2005. There is no mistaking this majestic planet, which dominates the evening sky shortly after sunset. This is a time known as twilight, where the Sun has gone down but you can still see an orange glow coming over the horizon. Look up and to the left of where the Sun just went down to see Venus.
Unfortunately, we cannot take images of Venus using the Liverpool telescope because it's never really dark enough to take a clear picture. However, if you have your own small telescope or some binoculars, you may want to have a look for yourself, but make sure the Sun is below the horizon before you try.
December 21st - Shortest day or Winter Solstice
The winter solstice, or mid-winters day, is the point during Earth's orbit around the Sun where we (in the UK) experience the shortest period of daylight or, happily for UK astronomers, the longest night. Solstice literally means a stopping or standing still of the Sun. In summer (June 21st) it marks the longest day of the year and in winter (December 21st) the shortest. Around the world, both dates have had spiritual significance for thousands of years as humans have been amazed by the great power of the Sun, and the warmth and life that it brings. Stonehenge, shown below, is often a focus for solstice celebrations.
© Northlight Images
These changes in daylength is all down to the tilt of the Earth in relation to the Sun, and without it we wouldn't have any seasons. Of course countries in the southern hemisphere, like Australia and South Africa, will be having their longest day of the year on the 21st because they are tilted toward the Sun in December, whereas we are tilted away. If this is a bit confusing, try going to the spinning Earth section to see that the length of day is different depending on the time of year and on where you are in the world.
The Planets
Click HERE and start the Electric Orrery to see where all the planets are today in relation to each other.
MercuryMercury passed inferior conjunction (i.e. between us and the Sun) on the 24th November. At the start of December, it will appear as a very faint morning 'star' rising around 6 am toward the east-southeast. You will only have around 30 minutes to find it using binoculars before the sky becomes too bright with the rising Sun. You may also see Jupiter, which is a much brighter object that rises a good hour before Mercury does. Mercury reached greatest elongation (i.e. apparent separation from the Sun) on December 15th and will then quickly move behind the Sun.
VenusVenus remains clearly visible toward the south-southwest as a brilliant evening star and then slowly moves around in front of the Sun. It will reach maximum brightness on December 9th but will then get gradually dimmer even though it will be moving closer toward us. This happens because we start to see more of the dark side of Venus as it overtakes us on the inside. In the same way as we see phases of the Moon, we see phases of Venus; so by the middle of January we will have a "New Venus" and will hardly see anything. Why not try confirming this using the electric orrery.
MarsMars remains prominent throughout this month but will gradually start to diminish in size and brightness as Earth starts to move away. It can be found high above the eastern horizon shorltly after sunset and spends the whole night crossing the sky before finally setting in the west-northwest at around 4.30 am. Now is still a good time to look at Mars using the Liverpool telescope, as you should be able to make out some surface features.
JupiterJupiter remains on the other side of the Sun and unfortunately is not yet visible from the Liverpool telescope. If you are an early riser you should be able to catch a view of Saturn in the pre-dawn sky after it rises in the east-southeast shortly after 4 am. It will remain visible to the naked eye until the Sun rises a couple of hours later. The best time to view Jupiter this coming year will be in April, May and June.
SaturnSaturn continues to become more prominent in the night sky, rising in the east-northeast around 8:30 pm and reaching high above the southern horizon around 4 am in the morning. Over the month, this will move earlier into the evening as we slowly start to catch up Saturn because of our inside orbit. Still passing through the constellation of Cancer, Saturn is a reasonable target to observe with the Liverpool Telescope using Go Observing, and this will continue to be the case for the next few months. The best opportunity to observe Saturn will come at the end of January 2006.
Constellation of the monthEach month, new constellations are highlighted for you to identify in the night sky.This month, we are going to look for the constellation of Pereus, named after the Greek hero who slayed the Medusa. Perseus is one of the more prominent winter constellations and can be found high in the sky above our heads around 10 pm. Try to find the planet Mars first and then look up and left a bit for the central bright star Algol, which represents the eye of the Medusa.
 December Night Sky Algol is not the brightest star in the constellation, but it is certainly the most famous one with astronomers. Algol (from Arabic al-Ghul, which means The Ghoul or The Demon Star) is the prototype of a whole group of eclipsing variable stars. This means that it's actually two different stars orbiting very close to each other and where each blocks out some of the light from the other in turn. The star system contains a bright blue star, Algol A, and a cool dark star, Algol B, which orbit around each other every 2.85 days.
 Algol Eclipsing Binary Star Because the Algol stars are so far away, we can only see one point of light. However the brightness of this point source varies when the stars eclipse each other. The graph above shows how the light changes with each eclipse. The primary eclipse is where the cooler, darker star blocks out lots of light from the hotter, brighter star. The secondary eclipse is where the reverse is true. Because the cool star doesn't emit much light in the first place, blocking it out doesn't make a huge difference to the overall light. Astronomers have used these unique stars to find out about nature of stars throughout the galaxy. Mythology: Perseus Perseus was an ancient Greek hero. His mother was Danae, the daughter of Acrisius, the king of Argos. When a prophecy revealed to Acrisius that his grandson would kill him, Acrisius imprisoned his daughter Danae so that she remained a virgin. Zeus, however, fooled Acrisius' precautions by entering the prison disguised as a shower of gold. When Acrisius discovered that Danae had given birth to Perseus, he had the mother and the son thrown into the sea in a chest of wood. Luckily they reached the island of Seriphos where the king Polydectes offered them hospitality and protection. Perseus was secretly raised on the island and became a courageous young man and was sent to complete a dangerous mission. Perseus had to fetch the head of the Gorgon Medusa who could turn anyone who looked at it eyes into stone. With the help of Hermes, Perseus succeeded. On his voyage back to Seriphos, he met the beautiful Andromeda in Ethiopia and married her. When his triumph became known, he was invited to the city of Larissa to participate in funeral games in honour of the king.
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