Guest Post by Glen Ward / Starry Mirror

Hello Stargazers —

A wonderful event is occurring in the heavens early this Summer, and you can see it with your own eyes on any clear evening.

The planet Mars has just experienced an “opposition.”   And what’s more, it’s hanging up there close to a couple of other old friends: Saturn and the bright star Antares!

“Opposition” is just a fancy way of saying that the Earth is passing between Mars and the Sun. Our planet is a bit closer to the Sun than Mars, and every two years or so we catch up to the Red Planet, overtake it, and keep on going around. For a few weeks around opposition, Mars gets very bright and becomes large enough to show details in small Earthbound telescopes.  The patient observer -- retuning for a look every few nights over the course of the next month or so -- will also see the red planet go retrograde -- appear to move backwards against the background of fixed stars.  This effect is really wonderful to behold.  The old ZigZag.  I think that's what Aristotle called it.

This Summer, if you go outside shortly after dark and you look low in the South, you can’t miss Mars. It is a bright orange “star,” the brightest star in the Southern sky. Look a little to its left, and you will see two other bright stars. The higher up of this pair is none other than Saturn, and the lower star is Antares, in Scorpius. Antares’ name means the “anti Mars,” or the “equivalent of Mars.” So, Mars is meeting its twin – or its nemesis – this Summer!

Most of the time, Mars is no brighter than Antares, and they look almost identical in color and brightness. But during this time of opposition, Mars is much brighter. In late April, Mars approached very close to Antares heading Eastward, and the planet came to a standstill. Then it began moving West, to the right, against the stars. This is the famous zig-zagging “retrograde motion” for which Mars is famous, and which is really caused by the Earth’s own motion in “passing up” Mars. By early July, Mars will begin moving Eastward again – to the left - against the starry backdrop. So, in late August Mars will appear to pass very close to Antares for its second time this year!

These days, most new learning about Mars comes from space probes. But astronomers around the world still enjoy watching the planet around opposition. During the Golden Age of Observational Astronomy – the Victorian Era – Earthbound observation of Mars was a new frontier. Astronomers of the time gave fanciful names to the mysterious green shadings seen on the planet, like the Juventae Fons (Fountain of Youth,) the Solis Lacus (Lake of the Sun,) or the Syrtis Major (after the Gulf of Sidra, in Libya.) And, the astronomer Percival Lowell imagined these features were part of a planet-wide system of waterways which he believed indicated an intelligent Martian civilization. Today we know that there are no canals, lakes or gulfs on Mars, and these areas are mostly just “albedo features” - areas of darker shading. But, astronomers still enjoy looking for these famous Martian locales. Watching the Red Planet gives us a link to the times when there was more mystery, more room for romantic ideas, in science.

Let’s not forget about our friend Saturn, which is spending all of 2016 hanging out above Antares. It’s a yellow “star,” just a little brighter than Antares. Because Saturn is so much more distant than Mars, it appears to move against the starry backdrop much more slowly. Saturn was at opposition in early June, but the ringed planet’s great distance means that opposition makes only a little difference in how big and bright it looks. Still, the planet and its rings are a pretty sight in even very small telescopes. If you have any little telescope around, no matter how humble, try pointing it at Saturn. You may get a surprise you’ll never forget.

If you are outside looking at this great conjunction of stars and planets in the Southern sky, you might notice another very bright-yellow “star” low in the West – It’s Jupiter! The biggest planet will hang out in the evening sky until mid-Summer, before it passes behind the Sun – “conjunction” – in September. Jupiter has four Moons around it which were discovered by Gallileo. Any little telescope or even some binoculars can show these Moons as little stars near the planet, so you might want to check it out.