Look for the Moons of Jupiter


Face south after the sky has completely darkened, and look for the brightest point in the heavens. The steady light, even on a cold night when all the other stars seem to be twinkling indicates it is one of the planets. The brilliance and the time of night narrow the choices down to Jupiter, the largest world in our solar system.

Jupiter is a planet that is nearly 11 times as wide as the Earth, with a volume that could swallow our planet more than 1,000 times. But Jupiter is very far away, so it appears as nothing more than a brilliant star in the night sky until you magnify the view a little bit. It doesn’t take much magnification to see Jupiter is different from the stars; a pair of binoculars will do the job.

When you look at stars in binoculars, even the very brightest ones, they appear as the tiniest pinpoints of light. Stars are so far away that even the most powerful telescopes can only show a handful of the closest stars as anything more.

When you look at Jupiter with binoculars, the speck of light grows into a tiny circle or disk shape, still not very big, but clearly bigger than any star. And if you can hold the binoculars really steady by bracing your elbows or using a camera tripod, you may be able to see up to four tiny stars lined up next to the planet’s disk. These tiny stars are the four biggest moons that circle around the planet. The moons were discovered by Galileo Galeli in January, 1610, at a time when Jupiter was just a little farther East of where we find it this year.

Galileo used a telescope about 4 times as powerful as a pair of binoculars to view the planet. If we view Jupiter with an inexpensive telescope that can magnify the tiny disk of the planet by 80 times, twice as powerful as Galileo’s telescope, in addition to the moons we can detect faint dark bands crossing the planet. The dark belts and light bands are the tops of the clouds that surround this huge gas planet. With sharp eyes, you may even be able to detect a faintly reddish oval between one of the dark belts and the adjacent bright band. This oval is Jupiter’s Great Red Spot, a hurricane like storm that has been swirling  in Jupiter’s clouds as long as there have been telescopes powerful enough to see it.

Better views of the planet were provided by the six space probes that have visited Jupiter. Two Pioneer space probes returned the first close up images as they flew past the planet, followed a few years later by the two Voyager space probes. The Galileo probe orbited Jupiter more than two dozen times before plunging into the planet’s atmosphere. And as the Galileo mission was nearing its end, the Cassini space probe sped by, calibrating its instruments on Jupiter before heading on to Saturn.

While you can look at the pictures taken over the years through telescopes and by space probes, there’s still a special thrill to looking up at the blazing planet in the night sky and knowing you have Jupiter in your sight. Jupiter, the largest planet in our solar system, will remain visible in the evening sky until the last snow of winter has fallen.

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