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An Independent Monthly Newsmagazine Serving the Community since 1989


Save our skies

Be a considerate neighbor: Reduce glare. Shield all your outside lights downward (or turn them off completely) and enjoy the beautiful, starry night sky.

Red Jr.
Red Jr., a youngster of a storm, only six years old, will pass by the Great Red Spot, around the Fourth of July of this year.

July 2006 Night Sky

Well, actually Earth has several “moons” in orbit, at least temporarily. It seems that asteroid-sized objects have been captured temporarily by earth's gravity. Astronomers know of at least four: 2003 YN107, 2002 AA29, 2004 GU9, and 2001 GO2.
These asteroids are not truly captured by Earth's gravity. From our point of view, it only looks like we have a new moon. These asteroids are called earth coorbital asteroids. They actually share Earth's orbit with the Sun, taking almost a year to complete an orbit. Occasionally a coorbital catches up to Earth from behind, or Earth will catch up with it, and the dance begins. The asteroid, while still in orbit around the Sun, slowly corkscrews around our planet.

At the moment, only two coorbital asteroids are nearby: 2003 YN107 and 2004 GU9. The others are scattered around Earth's orbit. 2004 GU9 is the most interesting. It measures about two hundred meters across—relatively large. And according to calculations just published in the Monthly Notices of the Royal Astronomical Society (S. Mikkola et al., 2006) it has been looping around Earth for five hundred years, and may continue looping for another five hundred. It's in a remarkably stable orbit.
But, right now, astronomers are paying more attention to 2003 YN107 for one simple reason: it's about to leave orbit. The asteroid, only 650 feet in diameter, arrived in 1999 and began corkscrewing around Earth. But, the asteroid's path is lopsided, and on June 10, it dipped within 2.1 million miles of Earth, slightly closer than usual. At that point, Earth's gravity gave the asteroid just the nudge it needed to leave.

2003 YN107 won't be gone forever. In about sixty years it will lap Earth again, resuming its role as a temporary moonlet. Astronomers calculate that a close pass with Earth more than a century from now finally will kick 2003 YN107 into a normal, circular orbit. Over the course of time, other coorbital asteroids will also come and go.

For now, coorbitals are just a curiosity. Someday, when the space program is more advanced, it might be possible to visit and explore the moonlets, perhaps even tap their resources.

Jupiter's most familiar feature is a swirling mass of clouds that are higher and cooler than surrounding ones. It is called the Great Red Spot. The spot has been compared to a gigantic hurricane and is caused by tremendous winds that blow on the rapidly spinning planet. Winds circulate around the spot counterclockwise at about 250 miles per hour. Hurricanes on Earth rarely generate winds over 180 miles an hour. The Great Red Spot is twice the size of Earth and has been raging for at least three hundred years. But it is only one of several storms on Jupiter.

Red Jr. is a youngster of a storm, only six years old. Compared to the Great Red Spot, Red Jr. is half-sized, but it blows just as hard as its older cousin. Red Jr. has not always been red. For five years, 2000 to 2005, the storm was pure white like many other small white ovals circling the planet. In 2006 astronomers started to notice a change. A red vortex formed inside the storm, the same color as the powerful Great Red Spot. This was a sign, researchers believed, that the spot was intensifying.

Now, the two storms are converging. Their closest approach is predicted to occur on the 4th of July. It will not be a head-on collision, and the Great Red Spot is not going to “eat” Junior. But the storms' outer bands will pass quite close to one another. No one knows exactly what will happen as they pass each other.

Similar encounters have happened before. Red Jr. and the Great Red Spot pass each other approximately every two years. Previous encounters in 2002 and 2004 were anticlimactic. Aside from some "roughing" around the edges, both storms survived apparently unaltered. This time might be different. Some researchers think Red Jr. could lose its red color, ironically, by passing too close to the Great Red Spot.

• You can try and spot Mercury low in the west after sunset, until July 6. Mercury will be showing itself again the last half of the month low on the eastern horizon before sunset. As always, Mercury is difficult to spot. Starting July 25, look for this planet to rise about 5:30 a.m.
• Venus is our bright morning star hovering above the eastern horizon before sunrise around 4:00 a.m. The waning crescent Moon joins Venus on July 22.
• Mars is located above Saturn in the western evening sky after sunset. It sets about 10:45 p.m. early in the month. Late in the month it will set about 9:30 p.m. Look for the waxing crescent Moon to pair with Mars on July 27.
• Jupiter can be found high overhead at sunset. Look up. It is the brightest “star” in the sky. The bright half-moon will be just below Jupiter on July 5.
• Saturn will be hugging the western horizon after sunset. Look for it to set about 10:30 p.m. early in July and by 8:30 p.m. by month's end.
• The Moon is full on July 10 and new on July 24.

If you have a question, comment, or suggestion for Charlie, e-mail him at


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