Jupiter and Saturn put on a ‘once in a lifetime’ show in December

Sky watchers will be in for a rare treat, as Jupiter and Saturn get so close that they will almost appear to be a single bright planet in the sky.

Saturn has been tracking Jupiter across the night sky for the past few months.

The two planets will get closer and closer over the next three weeks, until they appear together at 13.33 UTC on December 21, which in New Zealand will be around 2 a.m. on December 22.

This event, known as a grand conjunction, occurs approximately once every 20 years.

But the closeness of the two planets makes this a very rare conjunction.

With only one-tenth of a degree separating the two planets, which is one-fifth the width of the Moon, this is the closest they will have appeared in the sky in nearly 400 years. The last time it happened was in 1623.

They will be so close to each other that you can see them with a telescope eyepiece, says Andrew Jacob, curator of the Sydney Observatory.

“I’d be lucky to see this once in my life,” he says.

The two planets won’t reappear this close to each other until 2080.

While the planets look close from Earth, they are actually separated by great distances as they orbit the Sun.

From Earth we see that the planets move from east to west across the sky along the same narrow band as the Moon and the Sun.

While Saturn takes almost 30 years to complete one orbit, Jupiter takes almost 12 years, so we see Jupiter circling Saturn every 20 years.

How far apart they appear each time depends on how the tilt of the orbits of the two planets is aligned.

But you don’t have to wait until December 22 to enjoy both planets.

When is the best time to see the planets?

From now on, Jupiter and Saturn will come remarkably close night after night over the western horizon in the evening twilight.

“This is a good opportunity to see the movements [of the sky] in action, “says Jacob.

Astrophotographer Anthony Wesley has been observing the two planets from his Rubyvale property in central Queensland.

“I think they will actually look their best from a naked eye perspective only in the first week of December,” says Wesley.

“They are a little bit higher in the sky and if people are in towns with street lamps, you have a little more chance of seeing them before they get too low.”

As the weeks progress, Saturn gets closer to Jupiter, but both planets get closer to the western horizon and the sun sets later.

With a crescent Moon starting on December 17, the planets, now a finger apart, will put on a pretty sight, says amateur astronomer Ian Musgrave.

“That will look particularly spectacular both with the naked eye and with binoculars and telescopes,” says Musgrave.

Fun fact: if you keep your left fist extended with your arm extended and cover the Moon with the knuckle of your index finger, you will not only hide Jupiter and Saturn, you will block almost 80% of all known moons in our solar system. system, (as well as Pluto, which will be under your little finger but too small to see).

What to look for

Assuming the weather is clear, you will be able to see the planets even in light-polluted areas without any equipment.

With the naked eye, look for two spots: the smaller Saturn appears to be chasing the larger, brighter Jupiter.

On December 22, the two planets get so close that you may not be able to see the gap between them, Musgrave says.

“The simple fact that you can look at a point and say ‘they are two planets separated quite close to each other’ is going to be amazing,” he says.

Wesley hopes to get a good view of the event from [central Queensland].

“There is nothing here but dirt and kangaroos, so I have no problem seeing them all the way to the western horizon,” he says.

Wesley has captured amazing images of the planets using a high-speed video camera attached to an 8-meter telescope.

However, with binoculars or a small or medium telescope, you will be able to pick up details like Jupiter’s four largest moons, he says.

“The innermost moon, Io, only takes three days to make a full orbit. So even in the space of an hour or two, it moves quite noticeably compared to the other moons,” says Wesley.

With a small telescope, you could pick up details like the two dark bands on either side of Jupiter’s equator, and if you’re lucky, you can even make out the big red spot.

“Jupiter only takes about 9 hours and 40 minutes to make one complete rotation, so at some point in each of those rotations it is facing Earth,” Wesley says.

There are online apps and calculators that you can use to see when the red dot is in front of Earth when the planets are above the horizon in the night sky where you live.

You will also be able to see Saturn’s rings and a couple of its moons, like Titan, through a small telescope.

“Saturn’s rings are the same size as Jupiter, so even with a moderately small telescope you will see Saturn and you will see the rings,” he says.

Geminid meteor shower in mid-December

December is also the month to see the annual Geminid meteor shower.

And this year, with no moon to erase the view, is bound to be insane.

The meteor shower, caused by Earth passing through a debris trail created by the asteroid 3200 Phaethon, will be at its best on December 14-15 in New Zealand.

“If you look north, it is very easy to see Castor and Pollux [the two bright stars of Gemini].

“The radiant of the Geminids is just below Castor, and to one side you have Orion and Taurus.”

– ABC