Photograph by NOAO/AURA/NSF/T.A. Rector (University of Alaska Anchorage) 
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M81, the spiral galaxy on the left, and M82, the galaxy on the right, are two relatively close galaxies that lie near the Big Dipper within the constellation Ursa Major, the Great Bear.

Photograph by NOAO/AURA/NSF/T.A. Rector (University of Alaska Anchorage) 

This Week’s Night Sky: See a Dramatic Eclipse—Off Jupiter

Two Jovian moons give a quick shadow show, and the Big Dipper points the way to distant galaxies.

Dark moonless nights this week promise great views of disappearing acts off Jupiter and of sparkling deep-sky treasures.

Io eclipses Europa.  Late evening on Monday, April 13, binocular and telescope users get a chance to witness a dramatic eclipse between two of Jupiter’s largest and brightest moons, Io and Europa.  

From 9:29 p.m. to 9:33 p.m. EDT, the shadow of the volcanic moon Io will darken its neighbor, ice-encrusted Europa, which will dim by as much as 2.3 magnitude.

Jupiter meets the crab.  Late on Wednesday, April 15, the brightest star-like object will be Jupiter, which will appear near overhead in the southern sky. With the moon having set earlier, this is a great time to use the gas giant as a convenient guidepost to hunt down the bright Beehive star cluster in the crab constellation Cancer.

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Look toward the southwest for brilliant Jupiter pairing up with the Beehive star cluster in the constellation Cancer, the crab.

The Beehive, or Messier 44, lies just 5 degrees northwest of Jupiter, which is equal to about the width of your three middle fingers when held at arm’s length.

Binoculars will show both planet and star cluster within the same field of view, but don’t let their apparent proximity to each other fool you. While Jupiter lies a respectable 41 light-minutes from Earth, the Beehive cluster sits nearly 600 light-years away. Taking up as much heavenly real estate as two full moons side-by-side, the 1,000 member stars of the cluster actually stretch across more than 22 light-years of space.

Big Bear galaxies.  As night falls without a moon in the sky on Friday, April 17, look for the famous Big Dipper stellar pattern within the constellation Ursa Major to point the way to a pair of bright galaxies.

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This finder chart shows the pair of galaxies M81 and M82 just to the side of the stars of Big Dipper’s bowl. The pattern will appear high in the northeast evening sky.

Messier 81 and Messier 82 form a beautiful galactic pair that can be easily hunted down with binoculars and backyard telescopes--even from light-polluted suburbia. First, identify the Big Dipper, which, at this time of year, is visible on its side high in the northeast sky in the early evenings. You’ll find these two galaxies sitting 10 degrees (equal to the width of your fist at arm’s length) to the side of the two end stars in the bowl.

M81, a giant spiral galaxy that is tilted towards Earth, is the brighter of the two galaxies, shining at magnitude 6.8. It looks like a fuzzy oval patch of light under high magnification. Its spiral arms can be discerned with an 8-inch or larger telescope under dark skies.

Its neighbour M82, also known as Bode's Nebula, is an elongated, cigar-shaped galaxy that shines at magnitude 8.2, and is also an easy binocular target.

The two islands of stars are separated by about 130,000 light-years and lie about 12 million light-years from Earth.

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This finder chart shows the pair of galaxies M81 and M82 just to the side of the stars of Big Dipper’s bowl. The pattern will appear high in the northeast evening sky.

Moon meets inner planets.  Right after sunset on Sunday, April 19, look toward the low southwestern horizon for the razor-thin crescent moon forming a heavenly triangle with Mars and Mercury. Perched far above the trio is brilliant Venus, the brightest of the bunch.

Sky-watchers will have to be quick, though, as the moon, Mercury, and Mars will sink below the horizon within an hour after local sunset. Find a location that has a clear line of sight to the western horizon, and use a pair of binoculars to sweep the area just right of the moon. The two fainter planets will appear suspended in the sunset’s glare.

Happy hunting!

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