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., 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
—CHARLIE CHRISTMANN
NEWS FLASH—EARTH IS LOSING A MOON
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.
WHEN STORMS CONVERGE
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.
THE PLANETS AND THE MOON
• 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 k5cec@yahoo.com. |
