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Sun, 18 Sep 2016

Planets catch the eye

Saturn (top), with Antares below it and Mars to the left, seen on 31 August

With dusk getting earlier, people are starting to notice an unusual combination of bright stars low down in the south-south-west after sunset. Actually, it's one star and two planets that are lined up. And night by night, you'll spot changes in their positions.

The three objects are the planets Saturn and Mars and the star Antares. Saturn is highest, with the brighter Mars below it and to its left, and Antares at the bottom. Mars is the one that is doing most of the moving, as it is the closest to Earth. It's also much more obviously reddish in colour – maybe not blood red, as some fanciful descriptions suggest, but definitely on the ruddy side. Right now Earth is moving away from Mars so it's getting smaller, but it won't be as close again until 2018 so if you have a telescope, take a look now. Chances are you won't see much because of its low altitude, but if you get good, steady conditions you should see its disc, currently about 9 arc seconds across, and maybe a dark marking or two. Mars will actually be in the evening sky until well into next year, but getting smaller every month.

If you read something on the web about Mars being as big as the full Moon this August, take a look at our debunking page to find out why this old chestnut comes around every year!

Saturn is still worth a look through a telescope, as it is a bit higher in the sky than Mars, and appears larger in a telescope. If you want to see its famous rings you can still see them with any telescope magnifying about 40 times or more. 

Antares, the lead star in Scorpius, the Scorpion, is a red giant star, and its name means 'Rival of Mars' because of its reddish colour. Take a look and compare the two for yourself!


Added by: Robin Scagell