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Jupiter never ceases to amaze

July 5, 2007 12:35 am

WHEN I HEAR the word "king," I don't think of a singer, fast food restaurants, or a cartoon television show. Instead, I think of Jupiter, the king of the planets.

With its massive size and its 63 known moons, Jupiter resembles a mini-solar system. It is the largest of the "gas giant" planets of the outer solar system. Like the sun, it's composed mainly of hydrogen and helium.

Astronomers estimate that if Jupiter had been about 80 times more massive, it might have become a star like the sun.

Jupiter's cloud-covered atmosphere is an ever-changing myriad of colors and features, which vary as the planet spins on its axis, approximately once every 10 hours.

July offers fine views of the planet in the southern sky a few hours after sunset during the warm Fredericksburg evenings .

Truly a showpiece, it is impressive in even the most modest optical instruments. A small backyard telescope will show its two main cloud belts, its famous Great Red Spot, and its four largest moons.

Jupiter takes about 12 Earth years to circle the sun. That means a year on Jupiter, the fifth planet from the sun, is equivalent to about 12 of our years.

Several manmade robotic spacecraft have studied Jupiter. Some of these spacecraft include Pioneer 10 and 11 in the early 1970s, Voyager 1 and 2 in the late 1970s, and Galileo in the 1990s. Jupiter was photographed earlier this year by the New Horizons spacecraft as it flew by the planet on its way to a rendezvous with Pluto in the year 2015.

These exploratory spacecraft have discovered intriguing things on and around Jupiter--deadly radiation belts, a ring around the planet, lightning bolts in the planet's atmosphere and active volcanoes on Io, one of its moons.

Io resembles a cosmic pizza with its lava-covered surface. See this link for a great photo of Io: http://apod.nasa.gov/apod/image/9703/io970321_gal_big.jpg

In July 1994, Jupiter became a cosmic crash scene when comet Shoemaker-Levy 9 struck the planet. Jupiter's gravity was so strong that it broke the comet into several pieces before the comet fragments crashed into the planet. This was the first time that astronomers witnessed a live collision between two objects in the solar system.

I find it amazing that we humans were able to accurately predict the collision more than a year in advance.

From our safe vantage point on Earth in the summer of 1994, humanity witnessed several pieces of the comet collide with Jupiter. The results were far beyond any predictions or expectations.

After the initial collisions, the impact sites on the planet became visible as black spots in Jupiter's atmosphere. I was able to observe these "black eyes" on Jupiter using my 8-inch telescope long after the impacts occurred. Check out this image taken by the Hubble Space Telescope of one of the impact sites: http://www2.jpl.nasa.gov/sl9/image112.html

If Comet Shoemaker-Levy 9 had hit the Earth instead of Jupiter, the results would have been catastrophic for us. Life as we know it would have been permanently altered.

The comet's collision with Jupiter was a wake-up call for us on Earth. Luckily, Jupiter took the hit instead of the Earth. Will we be so fortunate again in the future?

As I previously mentioned, Jupiter is the king of Fredericksburg's skies this month. It is visible after sunset in the southeastern sky at the beginning of July and in the southern sky later in the month.

The planet Venus is still visible low in the west after sunset. Catch it this month before it sinks too low on the horizon to be seen. On July 16 and 17, the thin crescent moon will be close to Venus and dimmer Saturn about an hour after sunset in the western sky. If you are an early riser, check out the moon paired with Mars on the morning of July 9.

The Rappahannock Astronomy Club hosts monthly star parties where you can view the moon, planets and other celestial objects through amateur telescopes. For more information, go to http://www.raclub.org