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Starwatch: July sky makes stellar memories

Earth reaches aphelion — its farthest point from the sun — on Friday, July 6, when we’ll be 94.5 million miles from our parent star.

But while giving the sun a wide berth, Earth cozies up to Mars in spectacular fashion. And, like a series of opening acts, other solar system bodies present a parade of celestial pairings.

As the spring constellation Leo dives toward the sunset, the lion’s bright heart, Regulus, slips by Venus.

On July 9, the star passes just one degree — two moon widths — from the planet.

The morning of July 10, a waning moon rises close to Aldebaran, the eye of Taurus, the bull.

The evening of July 15, a young crescent moon of the next cycle makes a lovely companion to Venus. The moon goes on to visit Jupiter on July 20, Saturn on July 24 and Mars on July 26 and 27.

At 12:07 a.m. July 27, Earth laps Mars in the orbital race. Mars is then at opposition — or opposite the sun in the sky — so it will be up all night. However, that night, the moon will be near Mars and almost full — plenty bright enough to steal some of Mars’ luster.

The evening of July 27, July’s full moon rises even closer to Mars, but as the most distant full moon of 2018, it won’t look especially big.

Three nights later, at 2:50 a.m. July 31, Earth sweeps to just 35.79 million miles from Mars. This will make Mars the closest and brightest it’s been since summer 2003, when our two worlds made their closest approach in nearly 60,000 years. By then, the moon will have waned and moved eastward far enough to give Mars a decent head start getting into the sky. Look for Mars in the southeast after the sky has darkened. If you’re on a calm body of water, enjoy its shimmering reflection.

Shining above Mars, the Summer Triangle of bright stars is now well up in the east after nightfall.

Brightest is Vega, in Lyra — the lyre — at the northwest corner of the Triangle.

Below Vega is Altair, in Aquila — the eagle — the southern point of the Triangle.

And in the northeast corner, Deneb anchors the Northern Cross, which outlines the graceful form of Cygnus, the swan.

West of the Triangle, brilliant Arcturus, in kite-shaped Bootes — the herdsman — outshines even Vega.

Immediately east of Bootes hangs Corona Borealis, the northern crown. Its neighbor to the east is an hourglass of stars marking the upside-down body of Hercules.

With all these bright stars and planets up at the same time, this July’s evening sky promises to be one of the most memorable.

The University of Minnesota offers public viewings of the night sky at the Marshall W. Alworth Planetarium in Duluth. Visit d.umn.edu/planet.

Minnesota Starwatch is a newsletter describing the night sky in the Midwest. Updated monthly, it is produced by Deane Morrison, University of Minnesota Institute for Astrophysics. Find U of M astronomers and links to the world of astronomy at astro.umn.edu.

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