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KILLER PERSEID APP: You can now experience
the Perseid meteor shower on your iPhone. It's cloud-proof!
Learn more and give
it a try. |
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FULL MOON AND JUPITER:
Tonight, when the sun sets, go outside and look southeast. The full
Moon is having a close encounter with Jupiter. The two are so bright,
you won't even need a
sky map to find them. Moon shots: from
Anthony Ayiomamitis of Athens, Greece.
POSSIBLE PERSEID OUTBURST:
This year's Perseid meteor shower could
be even better than usual. "A filament of comet dust has drifted
across Earth's path and when Earth passes through it, sometime between
0800 and 0900 UT (1 - 2 am PDT) on August 12th, the Perseid meteor
rate could surge to twice its normal value," says Bill Cooke
of NASA's Meteoroid Environment Office. The following profile is
based on the debris stream models of veteran forecasters Jeremie
Vaubaillon and Mikhail Maslov:
The filament was shed by Perseid parent comet Swift-Tuttle
in the year 1610, and this is one of Earth's first encounters with
it. "In addition," notes Cooke, "the main Perseid
debris stream, which we run into every year, may be denser than
normal due to a gravitational enhancement by Saturn. The total combination
of these effects could result in as many as 200 meteors per hour
(ZHR)."
Bright moonlight will overwhelm the outburst's fainter
Perseids, but even a fraction of 200 is a good show. Science@NASA's
"The
Perseids are Coming" offers observing tips and sky maps.
SWIRLING DEBRIS ON
JUPITER: The "Wesley impact cloud"
on Jupiter continues to expand and evolve. On August 1st and 2nd,
worldwide observers noted that it had transformed from a concentrated,
cindery-black spot to an Earth-sized paling swirl. South is up in
this just-updated Aug. 3rd image from the cloud's
discoverer, Anthony Wesley of Murrumbateman, Australia:
"Polar winds seem to be carrying the main body
of the cloud westward (to the right in the photo)," says Wesley.
"Also, a small stream of dark material is being pulled down
and in the opposite direction--perhaps around a cyclone or some
other localized weather feature?"
Researchers are scrambling to study the cloud before
it disperses. Light reflected from the debris may hold clues to
the nature of the mystery-impactor.
"If the cloud's spectra contain signs of water, that would
suggest an icy comet. Otherwise, it's probably a rocky or metallic
asteroid," says JPL planetary scientist Glenn Orton. Several
teams of professional astronomers are working to obtain the data.
Meanwhile, amateur astronomers can monitor the cloud as it shifts
and swirls near Jupiter's System II longitude 210°. For the predicted
times when it will cross the planet's central meridian, add 2 hours
and 6 minutes to Sky and Telescope's predicted
transit times for Jupiter's Great Red Spot. [sky
map]
more images: from
Raffaello Lena of Rome, Italy; from
Glenn Jolly of Gilbert, Arizona, USA; from
Wah! of Hong Kong; from
William Rison of Newburg, Maryland; from
Joel Warren of Amarillo, Texas; from
David Kolb of Lawrence, Kansas; from
Alphajuno of League City, Texas; from
Mariano Ribas of Buenos Aires, Argentina; from
Giancarlo Ubaldo Nappi of Belo Horizonte, Minas Gerais, Brazil
2009
Noctilucent Photo Gallery
[previous years: 2008,
2007, 2006,
2005, 2004,
2003]
July
2009 Aurora Gallery
[previous Julys: 2008,
2007, 2006,
2005, 2004,
2003]
Explore
the Sunspot Cycle
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