May 20, 2016

Red and Golden Planets at Opposition

Earth is about to lap Mars and then Saturn in their race around the sun. The two planets have gathered together in the constellation Scorpius where they are shining brightly in the evening sky with Mars gleaming burnt orange and Saturn golden yellow.


The action begins with Mars. On May 22, 2016, Earth will pass directly between the sun and the Red Planet. Astronomers call this event "the opposition of Mars" because the sun and Mars will be on opposite sides of the sky.

Oppositions of Mars happen every 26 months. The racetrack model of planetary orbits explains why. Earth and Mars are like runners on a track. Earth is on the inner path; Mars is on the outer one. Every 26 months, speedy Earth catches up to slower Mars and laps it. Opposition occurs just as Earth takes the lead.

Because planetary orbits are elliptical, not all oppositions are the same. In 2003, Earth made its closest pass by Mars in 50,000 years when it passed just 34.6 million miles away. During this year’s opposition Mars will pass only 47 million miles away. The next opposition – in 2018 – will be even closer at 35.8 million miles away. The 2003 opposition was an apparition that mesmerized sky watchers all over the world. This opposition in 2016 will be the closest the two planets have been to one another since that historic event.

To see Mars, just step outside after sunset and look towards the Southeast. It is reddish and bright --and it's not alone.

Just to the left of Mars is a golden luminous body, not quite as bright as the Red Planet but still eye-catching. That's Saturn!

The ringed planet is having an opposition of its own. Saturn will be closest to Earth and opposite the sun on June 3rd at 840 million miles.

Both planets are at their best view during the last week of May and first week of June. Framed by the bright stars of Scorpius, they are a spectacular sight to the naked eye and can be seen even better with a small telescope. The rings of Saturn are easy to see through backyard optics. Ditto for the ruddy disk of Mars. The Red Planet is just finishing winter in its southern hemisphere so be alert for a bright polar cap at the Martian south pole!

You may also notice a bright star near Mars and Saturn. That's Antares, a red supergiant star. If Antares replaced the sun in our solar system, its surface would extend beyond the orbit of Mars. Writers sometimes call Antares "the rival of Mars" because the two look so much alike in brightness and hue. If you look closely, however, you'll see that Antares twinkles like a star while Mars does not.

Mars, Saturn, and Antares form a must-see triangle in the late spring sky. Not to be outdone, the nearly full Moon comes into the field of view from May 20-23. About an hour and a half after sunset, look for the Moon in the Southeast as it passes right by the celestial trio. Mark your calendar and take a look!

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