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NO IMPACT: A coronal mass ejection (CME) propelled into space by the magnificent flare of June 7th has either missed Earth or its impact was too weak to notice. According to NOAA forecasters, the chance of geomagnetic storms during the next 24 hours has dropped to 15%.
AURORAS ANYWAY: No CME, no problem. Even without an impact to provoke it, Earth's magnetic field experienced a brief storm during the early hours of June 11. "The aurora burst was so bright that it painted the entire sky in fluctuating shades of green," reports Einat B of Cat Lake, Ontario:
"The midnight sun is supposed to make aurora viewing nearly impossible at this time of year, but these auroras were easy to see," he says.
Another episode of geomagnetic activity is expected on or about June 14th when a solar wind stream is due to hit Earth's magnetic field. High latitude sky watchers should remain alert for auroras. Aurora alerts: voice, text.
June 2011 Aurora Gallery
[Aurora alerts: text, voice] [previous Junes: 2010, 2008, 2001]
DROOPY DISH: Drivers traveling down Highway 395 in California's Eastern Sierra are accustomed to seeing a large white dish looming in front of the sandy-brown mountains. It's the 40-meter antenna at Caltech's Owens Valley Radio Observatory. On June 6th local resident Andrew Kirk was passing by the observatory when an extraordinary sight made him stop for a closer look. The antenna was apparently drooping and melting into the ground like a Dali watch:
"I realized I had seen a mirage image of the big dish," says Kirk, "so I went back to document it. Sadly, I had only a pocket camera with limited zoom. I improvised, though, and photographed the 'drooping dish' through one barrel of my binoculars. Amazingly, as I watched, the dish began to tilt upwards and within a few minutes it was pointing straight up. Had I passed a bit later I would have missed it."
According to atmospheric optics expert Les Cowley, the phenomenon was caused by "an abnormally warm air layer close to the ground that had a non-linear temperature gradient. The conditions were akin to stages of an Etruscan vase sunset mirage or the inferior mirages seen over sun-heated roads. Strictly speaking, however, this one was a distortion rather than a mirage because the latter is technically reserved for when there is more than one image of the distant object." A full discussion of the drooping dish may be found at Cowley's excellent Optics Picture of the Day website.
Kirk drives by the dish frequently and he's looking forward to a whole summer of warm air and temperature gradients. "I hope to see this again...with my better camera in tow."
Midnight Solar Eclipse Gallery
[NASA: A Rare Eclipse of the Midnight Sun]
Potentially Hazardous Asteroids (PHAs
) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones
all the time.
On June 11, 2011 there were 1224 potentially hazardous asteroids. Notes: LD means "Lunar Distance." 1 LD = 384,401 km, the distance between Earth and the Moon. 1 LD also equals 0.00256 AU. MAG is the visual magnitude of the asteroid on the date of closest approach.
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