Starwatch: Venus, Jupiter rule the May skies
Published 9:32 am Saturday, April 28, 2018
By Deane Morrison
University of Minnesota
All during May, Venus and Jupiter dominate the early evening from opposite sides of the sky.
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Earth laps Jupiter in the orbital race on the night of the 8th-9th, an event called opposition because it puts Jupiter opposite the sun in the sky. At that time, Jupiter rises around sunset and stays up all night. On the 10th, our two planets make their closest approach — about 409 million miles — before Earth leaves the giant planet behind.
The closest approach comes slightly later than opposition because during that short interval, Earth moves a little farther from the sun while Jupiter moves a little closer to it. Jupiter is brightest when it’s nearest, but it could be hard to see much difference. Because its orbit is so far beyond Earth’s, its distance from us doesn’t vary by a big percentage.
If you have a good pair of binoculars and can stabilize them, you may see up to four bright dots on either side of Jupiter. These are Jupiter’s largest moons — the Galilean moons, discovered by Galileo in January 1610. He deduced that they orbited Jupiter, a finding that dealt a blow to the old idea that everything in the heavens revolved around Earth. Look for Jupiter’s high-wattage orb in the east after nightfall and in the west an hour or two before sunrise.
Jupiter may be up all night, but Venus makes the most of its limited time above the horizon. Our sister planet comes out in the west shortly after sunset and brightens as it sinks toward the horizon. Try looking for Venus 60 or 90 minutes after sunset to catch it when it’s bright but not yet too low. On the 17th a young crescent moon joins Venus. Shining to the upper right of the pair that evening is multicolored Capella, the brightest star in Auriga, the charioteer.
If you want to compare Venus and Jupiter as they face each other across the sky, try the second week of May, when both planets will be fairly high and the moon won’t interfere.
The evening of the 21st, the bright star Regulus, in Leo, comes out right below a first-quarter moon. The morning of the 29th, the moon sets just a few hours short of fullness. But that follows a night when it crosses the sky between Jupiter and Saturn, with Mars taking up the rear. A morning planet, Mars is best seen about 90 minutes before sunrise, when it will be low in the south-southeast. Watch for Mars to brighten as its late-July opposition draws nearer.
The University of Minnesota offers public viewings of the night sky at its Duluth and Twin Cities campuses. For more information and viewing schedules, see:
Duluth, Marshall W. Alworth Planetarium: www.d.umn.edu/planet
Twin Cities, Minnesota Institute for Astrophysics (during fall and spring semesters): www.astro.umn.edu/outreach/pubnight.
Check out the astronomy programs at the University of Minnesota’s Bell Museum ExploraDome: www.bellmuseum.umn.edu/ForGroups/ExploraDome/index.htm.
Find U of M astronomers and links to the world of astronomy at www.astro.umn.edu.