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June 5, 2006: The two biggest storms in the solar
system are about to go bump in the night, in plain view of
backyard telescopes.
Storm
#1 is the Great Red Spot, twice as wide as Earth itself, with
winds blowing 350 mph. The behemoth has been spinning around
Jupiter for hundreds of years.
Storm
#2 is Oval BA, also known as "Red Jr.," a youngster
of a storm only six years old. Compared to the Great Red Spot,
Red Jr. is half-sized, able to swallow Earth merely once,
but it blows just as hard as its older cousin.
Above:
Jupiter's two red spots, photographed on May 28, 2006, by
amateur astronomer Christopher Go of the Philippines. [Larger
image]
The
two are converging. Closest approach: the 4th of July, according
to Amy Simon-Miller of the Goddard Space Flight Center who
has been monitoring the storms using the Hubble Space Telescope.
(Update: Since
this story was published, the convergence has slowed, delaying
closest approach to July 15th - 20th. --Dr. Tony Phillips)
"There
won't be a head-on collision," she says. "The Great
Red Spot is not going to 'eat' Oval BA or anything like that."
But the storms' outer bands will pass quite close to one another—and
no one knows exactly what will happen.
Amateur
astronomers are already monitoring the event. Christopher
Go of the Philippines took the picture above using his 11-inch
telescope on May 28th. "The distance between the storms
is shrinking visibly every night," he says.
Similar
encounters have happened before, notes JPL's Glenn Or ton,
a colleague of Simon-Miller. "Oval BA and the Great Red
Spot pass each other approximately every two years."
Previous encounters in 2002 and 2004 were anti-climatic. Aside
from some "roughing" around the edges, both storms
survived apparently unaltered.
This
time might be different. Simon-Miller and Orton think Red
Jr. could lose its red color, ironically, by passing too close
to the Great Red Spot.
Red
Jr./Oval BA wasn't always red. For five years, 2000 to 2005,
the storm was pure white like many other small "white
ovals" circling the planet. In 2006 astronomers noticed
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 Oval BA was intensifying.
 Right:
Red Oval BA photographed by astronomers using the Hubble Space
Telescope in April 2006. [More]
The
color of the Great Red Spot itself is a mystery. A popular
theory holds that the storm dredges up material from deep
inside Jupiter's atmosphere, lifting it above the highest
clouds where solar ultraviolet rays turn "chromophores"
(color-changing compounds) red. Oval BA turned red when it
became strong enough to perform the same trick.
Bumping
up against the Great Red Spot, however, could weaken Oval
BA, turning it white again. Simon-Miller explains: "We
believe the Great Red Spot will push Oval BA toward a southern
jet stream, which is blowing against the oval's counterclockwise
rotation." This would slow Oval BA's spin, possibly reversing
the process that reddened it in the first place.
What
will actually happen? "We'll see," she says. That's
what telescopes are for.
Note
to sky watchers: Jupiter is easy to find. It pops out of the
evening twilight before any other star, surprisingly bright.
Look for it halfway up the southeastern sky at sunset: sky
map.
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Author: Dr. Tony
Phillips | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
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