Saturn normally takes center stage among the planets. But this summer, Mars is grabbing most of the attention. If you haven’t seen it yet, treat yourself. Go out the next clear night and look to the southeast around 10:30-11 p.m. It’s that fiercely brilliant, orange star brighter than every other object in the night sky except the moon and Venus.
Tonight the nearly full moon stands above and to the right of the Red Planet. In a lovely coincidence, Mars will be at opposition tomorrow night (July 27), the same night as the moon is full. Opposition occurs when the Earth and Mars line up on the same side of the sun, and the two planets are closest. With Mars on one side of Earth and the sun on the other, from the ground the planet appears directly opposite the sun in the sky. The planets will rise around sunset and remain visible the entire night.
Because Mars’ orbit is noticeably elliptical (non-circular), it continues to approach the Earth for a time even as faster Spaceship Earth starts to pass it up. That’s why it will be slightly closer to us on 4 days after opposition on the 31st. How close? Only 35,785,537 miles (57,591,239 km) will separate the two planets at 2:51 a.m. CDT on July 31. That’s the snuggliest we’ve been with Mars since its last close opposition in 2003. And that’s why it’s SO bright these nights. The dust storm hasn’t hurt either. Dust is a good reflector of sunlight; since the planet-wide storm broke out in June, Mars has not only changed color from red-orange to yellow-orange, but it shines a few tenths of a magnitude brighter than predicted.
All this makes the planet a real eye-catcher especially when there’s no moon about to brighten the sky and rob Mars of its proper radiance. Dust still lingers all throughout the planet’s atmosphere, shrouding the interesting dark features on its surface. A pity because it’s the only planet of the two that have surfaces (all the others are dominated by clouds) that shows real surface details. And because Mars is so small — about twice the size of the moon — we can only see these clearly around the time of opposition.
If you’re using a telescope, try to observe Mars at every opportunity if only to witness one of the greatest dust storms on the planet this century. In the meantime, we’ll keep our collective chins up for the time hoping for that time when the dust will clear. Because Mars is close, its apparent size is also as big as it gets, 24.3 arc seconds. Jupiter, largest of the planets, spans 38 arc seconds. For context, the moon is 30 arc minutes across which is equal to 1,800 arc seconds. So Mars appears only 1.3% as large as the moon.
If you’ve seen Jupiter as a disk through a pair of binoculars, you can try to do the same with Mars. Daniel Costanzo, with the Washington Academy of Sciences, was able to discern Mars as a disk through his 8×56 glass. He recommends looking about a half-hour before sunrise and a half-hour after sunset, when the sky is still bright. Otherwise the glare of the planet in a dark sky makes it nearly impossible to see its true outline. Costanzo points out that you can do this activity even from the heart of a big city as long as you can find a clear sight line.
Mars’ low altitude makes it easier to hold the binoculars steady although attaching them to a tripod or holding them against a wall or post will provide the steadiest view. If you try succeed in this observational challenge, please let us know by leaving a comment.
Mars rides low in the sky in the constellation Capricornus. As described earlier, it pairs up with the Full Buck Moon on July 27. In another wonderful coincidence, that full moon will be totally eclipsed as seen from Europe, Africa, Asia, Australia and parts of South America. No will eclipse will be seen from North America because the moon enters Earth’s shadow Friday afternoon, before it’s risen for the U.S. and Canada. Lucky viewers from England on east will witness an amazing sight Friday night: a orange-red moon sitting atop a bright orange planet! For more details about the eclipse please check out my Sky & Telescope story.