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Saturn and Jupiter make special ‘Christmas Star’

Ben Smith and Donna Coutts, December 14, 2020 6:45PM PerthNow

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Comparison of the size of planets in our solar system, from the Sun on the left and then Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus. Neptune and Pluto aren’t visible in this picture. media_cameraComparison of the size of planets in our solar system, from the Sun on the left and then Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus. Neptune and Pluto aren’t visible in this picture.

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Our solar system’s largest planets are set for a once-in-a-lifetime overlap.

On December 21, Jupiter and Saturn’s orbital paths are set to cross, coming so close that they will appear as though they are a single shining planet in the sky.

The event is called a grand conjunction* and happens roughly every 20 years – but 2020 will be the closest the two planets have appeared intertwined since famous astronomer Galileo Galilei was alive in the 1600s.

Painting of Italian astronomer Galileo Galilei by Justus Sustermans in 1636 from the National Maritime Museum, Greenwich, London. media_cameraPainting of Italian astronomer Galileo Galilei by Justus Sustermans in 1636 from the National Maritime Museum, Greenwich, London, UK.

The conjunction or overlap happens because it takes Saturn nearly 30 years to complete one orbit of the Sun, but Jupiter takes nearly 12 years, so it laps Saturn every 20 years.

How close they appear to each other depends on how the tilt of the two orbits line up.

Fremantle Sidewalk Astronomy’s Hubert Rady said while the planets had been slowly moving towards each other for some time, this viewing would be a once-in-a-lifetime event.

“On the 21st (of December) they will look like (a) single planet to the naked eye*, if you point a telescope at them they’ll be in the same eyepiece, it will be quite an incredible sight,” he said.

“They will be low in the sky in the west, 15 degrees above the horizon, a heck of a long way away on the far side of the sun.”

Mr Rady said while Jupiter and Saturn had come close in recent years, notably 2000, you had to go back to 1623 to witness a Jupiter-Saturn conjunction as close as this.

“It’s because of how the orbits lie — they’re on a plane but not a perfect plane, they’re on angles. I think next time they’ll be fairly close will be 2060.”

The ring swirling around Saturn consists of chunks of ice and dust. Saturn itself is made of ammonia ice and methane gas. The little dark spot on Saturn is the shadow from Saturn's moon Enceladus. media_cameraSaturn. Image processing specialists have worked to provide this crisp, extremely accurate view that highlights the planet’s pastel colours. Bands of subtle colour distinguish differences in the clouds over Saturn, the second-largest planet in the solar system.

HOW TO SEE THE GRAND CONJUNCTION
From now until December 21, Jupiter and Saturn will get closer night by night above the western horizon in the evening twilight.

On December 17, the planets should look pretty close together in the sky with the crescent Moon.

By December 21, Jupiter and Saturn will appear in the evening twilight about half an hour after sunset. They will be visible for about an hour before disappearing below the horizon to the west.

The clearer the sky, the better the view will be and the further north you are in Australia, the longer they will be in the sky.

Without a telescope, look for two dots. Saturn will be the smaller planet appearing to follow the larger, brighter planet Jupiter towards the horizon in the west.

By December 21, you may not be able to see the two separately.

If your family is planning for a great view, think about somewhere you can go with few street lights and where there is a clear view of the western horizon.

Some astronomy groups and observatories around Australia will host viewing gatherings and in Western Australia, Mr Rady will be hosting a viewing and setting up telescopes at North Coogee’s dog beach in Perth from 7.45pm on December 21.

GLOSSARY

  • conjunction: two things joined together
  • naked eye: without a telescope, binoculars, microscope or other equipment

EXTRA READING

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Astronomers watch birth of new planet

QUICK QUIZ

  1. What is about to happen in this story?
  2. What will it look like?
  3. What famous astronomer lived in the 1600s?
  4. What happened in 1623?
  5. Which is bigger, Jupiter or Saturn?

LISTEN TO THIS STORY

CLASSROOM ACTIVITIES
1. Create a Flyer
This event has been described as ‘once in a lifetime’. Something like this you don’t want to miss! Some people have even called it the ‘Christmas Star’.

Encourage your neighbours to witness this astronomical event by creating a flyer about it. Include information that tells them what is going to happen and why it is so special, where they need to look in the sky, when/where they will get the best view and how long they need to wait to see it again. Along with any other information you feel is important.

Make sure you set it out so it is eye catching. Use emotive language to help convince your audience. This event is worth seeing!

Time: allow 40 minutes to complete this activity
Curriculum Links: English, Science, Critical and Creative thinking, The Arts – Visual Arts

2. Extension
Draw an artist’s impression of someone viewing this Grand Conjunction. Use information from the article to help you make it as realistic as possible. Think about where they might get the best view (what type of environment – beach, mountains, inner city?), where in the sky they should be looking and when (what will the sky be like then?) and what equipment they may be using.

Time: allow 30 minutes to complete this activity
Curriculum Links: English, Science, Critical and Creative thinking, The Arts – Visual Arts

VCOP ACTIVITY
Adjectives
An adjective is a describing word. They are often found describing a noun. To start with look at the words before the nouns.

Search for all the adjectives you can find in the article

Did you find any repeat adjectives or are they all different?

Extension: Pick three of your favourite adjectives from the text and put them in your own sentences to show other ways to use them.

Have you used any in your writing?

HAVE YOUR SAY: What would you most like to see in the night sky?
No one-word answers. Use full sentences to explain your thinking. No comments will be published until approved by editors.

Extra Reading in space