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Moon, Jupiter, Mercury next few evenings


Tonight for May 31, 2014

The giant planet Jupiter. Image credit: NASA/JPL/University of Arizona

The giant planet Jupiter, via NASA/JPL/University of Arizona

Look westward after sunset on Saturday May 31, 2014, and it’ll be hard to miss the crescent moon and Jupiter, fifth planet outward from the sun and largest of all the planets in our solar system. The moon and Jupiter rank as the brightest and second-brightest objects in the evening sky right now. The waxing moon will appear near this bright planet both Saturday and Sunday evenings.

If you’re blessed with an unobstructed horizon and clear skies, you might also catch the planet Mercury near the horizon around 60 to 75 minutes after sunset. Mercury will be below Jupiter and the moon. Binoculars may be helpful, but you might be able to see this planet with the unaided eye.

As you view the moon and Jupiter this evening, the moon appears bigger, but of course that’s just because it’s nearby. Jupiter is really about 26,000 times more massive than our moon! Jupiter is truly the giant world of our solar system. It contains more than twice the mass of all the other planets, dwarf planets, moons and asteroids combined. Jupiter has 318 times the mass of Earth – and Earth has 82 times the mass of the moon.

How do astronomers know the mass of Jupiter?

That’s why, although it’s five times the distance of our Earth from the sun, Jupiter shines so brilliantly in our night sky. Is it the brightest planet? No. If you could place the planets Venus and Jupiter side by side, you’d find that Venus is brighter than Jupiter. But Venus now shines in the east before sunrise and will remain a fixture of the morning sky until late October 2014. So, among objects that appear as “stars” to our eyes, Jupiter is now dominating the evening sky.

What is an astronomical unit?

Sizes of sun and planets to scale, but distances are not. Bill Nye demonstrates distances between planets

Sizes of sun and planets to scale, but distances are not. Click here to see Bill Nye demonstrate distances between planets

Bottom line: Watch the evening twilight sky Saturday night – May 31 – and you’re sure to see the bright planet Jupiter near the waxing crescent moon. The planet Mercury is below them. Jupiter and the moon will be close together Sunday evening, too.

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