Sun, 09 Apr 2017
A Close Encounter of the Planetary Kind
A simulation of the appearance of the Moon and Jupiter on 10 April, shown by Stellarium
On Monday evening, 10 April, there will be an eye-catching close encounter between a planet and the Full Moon.
As the western sky darkens after sunset on Monday evening, turn your back on it and straight away you will see a beautiful silvery full Moon hanging above the eastern horizon. Look a little more closely, and you will see a bright star shining just beneath it, too, This star is actually the planet Jupiter, which is dominating the sky through the night at the moment, and is particularly bright and attention-grabbing because it is at its closest to us for some time, and is at "opposition". That's the astronomical term for describing how it lies exactly opposite the Sun in the sky and so rises as the Sun sets. What it means for sky-watchers is that Jupiter is impressively big and bright in the sky, brighter than any other star or planet on view after dark. On Monday night the Moon will be so close to Jupiter that they will be such a striking sight together in the sky that lots of people will stop what they're doing to take a look at them, without knowing what the bright "star" is – but you'll know in advance!
It's important to understand that although the Moon and Jupiter will look unusually close together in the sky, they won't have moved any closer together physically; Jupiter hasn't drifted out of its orbit and moved closer to Earth! The two worlds will be very far apart, with Jupiter more than one and a half thousand times farther away than the Moon. (Jupiter will be 666 million kilometres away, but there's no supernatural or demonic significance in that, honest!)
This isn't a scientifically important, or even a particularly rare one; the Moon hangs around with bright planets in the sky very often, it just happens to be Jupiter's turn on this occasion. But the two worlds will be strikingly close together, and just before 11pm on Monday night will be only a degree and 25 arc minutes apart, which is just less than three times the width of the Moon. At that time the pair will easily fit in the same field of view through a pair of binoculars, and might even be visible together through a small telescope at low magnification. And if you own binoculars or a telescope you'll be in for a double treat, because as the Moon shines close to Jupiter you'll be able to see Jupiter's four largest moons all on the same side of the planet too, like four tiny stars in a row.
Stellarium's simulation of the appearance of Jupiter and its satellites on 10 April at 22h UT.
But if you own neither of those pieces of equipment, don't worry. This will be something you can enjoy with just your naked eye, right through the evening.
It will also be easy to photograph, too. Although the best results will be achieved using digital SLR or bridge cameras, which can be focused manually, be set to take time exposures and be mounted on tripods to keep them steady, it will definitely be worth trying to take a photo of the pair using the camera on your phone or tablet; you won't get the detailed images possible with the aforementioned more advanced cameras, but you should get something you'll be pleased with....
But again, don't worry about using equipment of any kind. If the sky is clear, just go outside and take a moment to look at this perfect pairing. It really will be a striking sight in the sky – a reminder of why sky-watching is one of the simplest, but most rewarding, hobbies there is.
By Tuesday night the Moon will have moved on further eastwards in its track across the sky, and its "close encounter" with Jupiter will be over, so cross your fingers for clear sky on Monday night so you can enjoy this celestial rendezvous.
Text: Stuart Atkinson. Illustrations: Paul Sutherland
Added by: Robin Scagell