Extremely Rare ‘Christmas Star’ Will Light Up The Sky This Month When Two Planets Align

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Extremely Rare ‘Christmas Star’ Will Light Up The Sky This Month When Two Planets Align

The ‘Christmas Star’ is also known as the Gas Giant’s ‘Great Conjunction’.

If you’re a bit of a stargazer, you will have noted that Jupiter and Saturn are slowly but surely getting closer to each other. This tends to happen every couple of decades as the gas giants wander the universe along their respective orbital paths. However, this year’s approach is much more special due to the earthly perspective from which we will be able to view their coming together. (Featured image: @curious_gage)

In fact, the last time Jupiter and Saturn were this close together was just after the invention of the first telescope. But back in 1623, most people would have missed the event due to the blinding proximity of the sun, which was just thirteen degrees away. Thus the last time this event took place in similar conditions to which we will experience the ‘great conjunction’ on 21 December was 800 years ago — way back in the Middle Ages.

How close will Jupiter and Saturn be to one another?

Pretty damn close.

The two biggest planets of our solar system will be just 0.1 of a degree apart in the sky, which to most of us doesn’t really say much. To give you a better idea though, 0.1 degree equates to roughly about one-fifth of a full moon. In other words, Jupiter and Saturn are going to be so close together that they will appear like they are one shining bright light in the night sky.

Credit: Pete Lawrence

Why the ‘Christmas Star’?

The fact that this great conjunction is taking place just days before Christmas is enough for the term Christmas Star to have been thrown about in the media. It has been theorised, though, that an even rarer conjunction of planetary bodies — Jupiter, Saturn and Venus — might have been the ‘Star of Bethlehem’ which the three wise men followed to meet baby Jesus in the manger 2000-odd years ago. Other theories for the ‘Star of Bethlehem’ include a comet, the planet Uranus and a supernova.

No matter the name given to this once-in-a-lifetime event, it is one that is exciting a great number of people. And it’s a pretty little bonus that it’s happening around Christmas time.


Speaking to Space Australia, Professor of Astrophysics at Swinburne University Alan Duffy said that ”seeing the planets approach one another over the coming nights until finally overlapping during the conjunction is a vivid reminder that our Solar system is a dynamic and ever-changing place” and ”that this is the closest approach, from our point of view, in four centuries and will not come this close again in my lifetime, (meaning) I will particularly treasure this reminder.”

How to see the Great Conjunction?

Surprisingly for some, and not for others, (but great news for all) this ‘great conjunction’ will be able to be viewed without the need for special equipment. However, the two planets will not be visible when they are at their absolute closest as they will have set behind the horizon by that time.

The best time to check out the conjunction will be around 9pm AEDT on Monday, 21 December. You’ll need to be quick, though, because they will disappear from sight just over an hour and a half later at 10:39pm. 

To really make the most of this extraordinary event, we recommend heading out of the city and escaping the light pollution. To find the best places to go, use this Light Pollution Map.

If you do have binoculars or even a very small telescope, you should get them out. Use them and you should also be able to see Saturn’s stunning rings, Jupiter’s large disc, and moons from both of these giants. You might even be able to get a photo of them together with the moon. Now, wouldn’t that be something to show your friends?

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