month’s planets

The King of the Solar System reigns supreme again at dawn

As long as you don’t mind getting up early or staying up late, this is a great month for you if you’re a Jupiter observer. The largest planet in our Solar System – so huge it could contain a thousand Earths with room to spare – rises well before the Sun and dominates the pre-dawn sky. It will be shining very brightly in the south east, much brighter than anything else in that part of the heavens.

From a location that's truly unaffected by light pollution, it will look like a distant blue-white lantern, and even if you’re looking at the sky from your garden in a light-polluted town or city it is so bright you simply won’t be able to miss it.

Jupiter has been visited by quite a few space probes now. The early Pioneers, and then the Voyagers, flew past the planet without going into orbit, but as they swept past they took hundreds of photographs, which gave us our first truly detailed views of its clouds and many of its moons. The more advanced Galileo and Cassini missions followed, each of those unmanned probes returning even more detailed views of the Jovian system, which many astronomers think of as a miniature Solar System in its own right, with Jupiter taking the place of a star.

Now the Juno probe is orbiting Jupiter, and although its polar orbit does not send it swooping past any of the gas giant’s extended family of 64 moons, it is sending back stunningly detailed views of the planet’s churning, curdled clouds as it flies over its poles. You can view those images for yourself every day, for free, on the Juno mission website.

All through this month, the planetary king will be close to Mars in the sky. As this month progresses the distance between the pair will decrease until they are less than six degrees – 12 Moon widths – apart on Christmas Day morning, and only two and a half degrees, or five Moon widths apart, at dawn on New Year’s Day. If you go for an early morning walk on Boxing Day, hoping to burn off some of your Christmas dinner’s calories, you’ll see the two planets shining just five degrees apart. You won’t need binoculars or a telescope to see the close approach either - it will be clearly visible to the naked eye.

This month Jupiter also has a fascinating close encounter with the Moon, which will be both fun to watch and great to photograph. If your sky is clear on the morning of 14 December, look for the waning crescent Moon shining to Jupiter’s upper right in the hours before dawn. Roughly 20 hours later, the Moon will have moved far enough along its orbit around the Earth, placing it to Jupiter’s lower left.