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Home » Space/Science

A favorable opposition. July 13, 2018 4:59 pm ER

Just a reminder, Mars will be in opposition on 25 July this year, that is, Sun, Earth and Mars will be in a straight line. This happens about every 26 months, as Terra runs up behind the Red Planet, passing it on the inside lane. This particular opposition is a really good one, since Earth is near aphelion, and Mars near perihelion. The distance between the two planets will be almost minimized, about 0.38 AU. Mars’ telescopic appearance will be almost maximum at 23″. It will be favorably placed for observation all night, rising about sunset, setting about sunrise, and crossing the meridian around midnight. It will be autumn in the Martian N hemisphere, and the S polar cap will be visible.

For a few weeks before and after opposition the planet will go into retrograde motion, doing a big loop-de-loop against the background stars as we rush past it. Go out with binoculars every night and trace its motion on the celestial sphere, its just simple perspective geometry, but it drove the ancients nuts! Don’t worry if its overcast on the 25th. The show will be great for a week or two before and after.

Mars will be in the constellation Capricorn, at Declination -26 degrees, and will blaze brightly at magnitude -2.6. Even at midnight, it will be low in the southern sky for you observers in the northern USA, but you can’t miss it.

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