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An independent monthly newspaper serving the community since 1988
  Night Sky
 

Enjoy the starry night skies
Be a considerate neighbor. Reduce nighttime glare. Shield your outside lights downward. Let the stars light up the night.

jUNE 2014 night sky

—Charlie Christmann

The Great Red Spot

The famous Great Red Spot is most likely the longest-lived storm in the solar system, dating back to before Italian astronomer Gian Domenico Cassini looked through his crude telescope in 1665. He was the first to describe a “permanent spot” on the face of Jupiter. German amateur astronomer Samuel Heinrich Schwabe made the first drawing of Jupiter’s “hollow” in 1831. Regular observations began with American astronomer Carr Walter Pritchett in 1878. Today, astronomers describe the spot as generally reddish in color and oval in shape, approximately 12,400 by 7,500 miles centered about latitude 22° south.

Observations of the red spot have shown its actual color varies over time, as seen through Earth’s telescopes, from salmon-red to gray, when it may blend indistinguishably into the coloring of the surrounding clouds. Meteorologists would call the phenomena an “anticyclonic circulation system,” or a high-pressure system in the southern hemisphere, with cloud tops extending above the surrounding cloud base. Even with wind velocities at the edge of the spot reaching 250 miles per hour, it takes about seven days to complete one rotation.

Why it has persisted for so long is a mystery. Computer simulations of Jupiter show a cyclone like the red spot should not last more than four years. Nor do the models help explain its coloring: sulfur, phosphorus or organic compounds have been suggested as the source of the red color. The Great Red Spot is not the only mysterious vortex. In fact, vortices in general, including ones in Earth’s oceans and atmosphere, often live much longer than current theories can explain. Evidently our models will need some revisions to better understand how these cyclones form and eventually die.

Back in the late 1970s, the Great Red Spot measured more than 14,500 miles across, with an area of over ten million square miles (two and a half times the area of the United States). Back then, it had a more circular shape. Recent observations show the spot’s diameter has shrunk, and has been shrinking since the 1970s at a rate of almost six hundred miles per year, and it is now much more oval shaped. But, why shrink now? Is it going to disappear? Scientists offer one big shoulder shrug as their answer.

In 2010, one brown-colored belt completely disappeared only to reappear seven months later. The same thing happened in the 1990s, too. The dynamics are complex and turbulent on the giant planet, with smaller swirls forming and dissipating; some even get swallowed up by the Great Red Spot.

Perhaps NASA’s Juno spacecraft, now past the orbit of Mars, and expected to arrive at Jupiter in 2016, will tell us more. Plans are for Juno to skim to within 3,100 miles Jupiter’s cloud tops for a closer look. JunoCam onboard the space craft will be used to give the public spectacular views of the planet close-up—maybe it will even see inside the Great Red Spot.

While the spot is still great enough to easily swallow Earth, that may change in the next few decades. It just does not seem right that our grandchildren may look through a telescope and not see the great red mystery on the face of Jupiter.


A big thanks

I enjoyed meeting the young ladies of Girl Scout Troup 10416 in May. They had a great time looking up at the night sky and learning about the visible stars and planets. And, they earned an award, too!


 
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