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Mon, 25 Sep 2017

Venus and Mars approach

Stuart Atkinson writes:

If you're up early on any morning over the next week and a half you'll be able to see a celestial close encounter in the sky before dawn. No, nothing to do with light-covered UFOs, and after seeing it you won't feel strangely compelled to make models of mountains out of mashed potato or dirt in your living room; this is a close encounter between two planets in the east before sunrise, and although the view will be very striking through binoculars or a small telescope, it's something you'll be able to enjoy watching with just your naked eye.

The two planets in question are Venus and Mars. Venus has been dominating the pre-dawn eastern sky as the "Morning Star" for a while now – so bright it's been impossible to miss – and Mars has been in the same part of the sky too, though much lower down in the sky, closer to the horizon, and a lot fainter than Venus, too. But over the next week or so these two worlds will appear to close in on each other. Note: they'll only appear to move closer together, it's purely a "line of sight" effect, they're not actually drifting closer together physically "out there" in space. They become a little bit closer every morning, until they will be so close together they will look like a very beautiful double star on the morning of 5 October. Less than a Moon's width apart on that morning, they will both fit comfortably in the field of view of a pair of binoculars and will both be visible in a low power telescope eyepiece too. And, of course, they'll be a very tempting photographic target for astro-photographers....

To see this close encounter, you need to be at your observing site by 05.15. That site should be somewhere with a low, flat eastern horizon, uncluttered by trees, buildings or hills. That's important because you don't want to head out somewhere only to find that there are things in the way in that direction hiding the planets from view. As soon as you get to your observing site you'll see Venus blazing away in the east, a very shiny silvery blue-white "star". You'll see Mars shining to its lower left, a much fainter orange-hued "star". As you eyes adapt to the darkness you'll see stars too - you'll see that the two planets are close to the "Sickle" of Leo (you might see it as a fish hook, or a back to front question mark) and you'll see the distinctive constellation of Orion over to the south-east too. But ignore all those stars for a while and just concentrate on the planets. See how they are very different in brightness and colour, and how they shine with a much steadier light than the surrounding stars too.

The charts below will show you how the planets will appear to drift together between now and the start of next month. The view you see will depend on the date you're out there looking. Hopefully you'll have a run of clear mornings, to let you watch the two planets approach each other, but more likely, for the UK, you'll only get a couple of views, so make the most of them.

Cross your fingers for clear sky on the morning of 5 October th, because that's when the two worlds will appear the most striking in the sky. It's important to say here that they'll actually be slightly closer on the following morning, the 6th, but on the morning of the 5th they'll appear almost one on top of the other, which will be a more striking sight to the naked eye. This will be when you want to have a pair of binoculars or a small telescope handy, so you can magnify the pair and really appreciate the differences in their colours and brightnesses. They really will look lovely through a small telescope magnifying just a couple of dozen times.

After the 6th Venus and Mars will drift apart again, remaining a very striking sight in the sky for another week or so.

Good luck seeing this "close encounter" and, as ever, let us know if you see anything – and send us any photos you take, we'd love to see them!

Click to enlarge this sequence of diagrams, made using Stellarium


Added by: Robin Scagell