Jimmy Westlake: Jupiter closest to Earth this week
Steamboat Springs — Long after the lovely Evening Star, Venus, has set, it is Jupiter who wears the crown when it comes to ruling our late night sky, shining brighter than any other object, except for the moon.
Jupiter reaches its closest point to the Earth for this year, called opposition, on Friday. Opposition occurs when the Earth passes in between a more distant planet and the sun, placing the two planets as close together as they can be. Opposition for a planet is much like a full moon — the planet rises at sunset, is highest in our sky at midnight and sets just as the sun comes up.
On the night of opposition, Jupiter will be a mere stone’s throw from Earth — about 405 million miles. It will remain a dominant star-like object in our evening sky from now through spring and summer.
Steady binoculars or any small telescope will reveal Jupiter’s four traveling companions, discovered by Italian astronomer Galileo Galilei in 1610. They are the four largest of Jupiter’s family of 67 moons; their names are Io, Europa, Ganymede and Callisto.
It is fun to keep watch on Jupiter from night to night as these moons constantly change their positions around the planet. Io makes a trip around Jupiter in only 1.77 days; Europa takes 3.55 days; Ganymede takes 7.16 days; Callisto takes 16.69 days. For comparison, our moon takes 27.32 days to orbit the Earth, so Jupiter’s moons are really whizzing around fast.
Ganymede and Callisto are among the largest moons in our solar system, each rivaling the planet Mercury in size. Io and Europa are smaller, more like the size of our own moon.
With a medium-sized telescope, you might also glimpse the two dark cloud stripes straddling Jupiter’s equator and maybe, with a little luck, Jupiter’s famous Earth-sized storm, the Great Red Spot.
This winter, Jupiter shines down on us from near the boundary between the constellations of Leo and Cancer. It is positioned just about midway between Leo’s bright star Regulus and Cancer’s fuzzy Beehive star cluster.
You really can’t miss it, though, because it is the brightest object high in the eastern sky after darkness falls. Jupiter even outshines winter’s brightest star, the Dog Star, Sirius.
Don’t miss the full Snow Moon rising right alongside Jupiter after sunset on Tuesday night and then a little east of Jupiter by Wednesday night. The full Crow Moon will return for an encore performance with Jupiter on March 2.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College’s Alpine Campus. His “Celestial News” column appears weekly in the Steamboat Today newspaper and his “Cosmic Moment” radio spots can be heard on local radio station KFMU. Check out Jimmy’s astrophotography website at http://www.jwestlake.com.
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