Metallic photos of the sun by renowned photographer Greg Piepol bring together the best of art and science. Buy one or a whole set. They make a stellar gift.
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DOUBLE ASTEROID FLYBY: It's notable when an asteroid flies past Earth closer than the Moon. Today, April 6th, two asteroids will do this. Newly-discovered space rocks 2011 GW9 and 2011 GP28 will zip through the Earth-Moon system at Earth-distances of 77,000 km and 192,000 km, respectively. Both are ten-meter class asteroids two to three times smaller than the Tunguska impactor of 1908. There is no danger of a collision.
ARCTIC AURORAS: The onset of spring has brought a growing twilight to the night skies of the Arctic. The sky may be bright, but the auroras are even brighter. Here is the view from northern Norway after "nightfall" on April 5th:
Photographer Øystein Ingvaldsen of Bø in Vesterålen was taking a late walk at the time of the display. "I did not expect to see Northern Lights," he says "but suddenly they appeared. This is the first time I have photographed auroras and a sunset all at once."
More Arctic lights are in the offing. A solar wind stream is buffeting Earth's magnetic field, and NOAA forecasters estimate a 15% - 25% chance of high-latitude geomagnetic activity during the next 24 hours. Aurora alerts are available here.
more images: from Frank Olsen on Hillesøy island outside Tromsø, Norway; from Valentin Clement and Guillaume Gravey of the Lofoten Islands, Norway; from Hanneke Luijting of Tromsø, Norway; from Chad Blakley of Abisko National Park, Sweden
April 2011 Aurora Gallery
[previous Aprils: 2010, 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002]
UNSTABLE FILAMENT: An active filament of solar magnetism is snaking around the sun's southeastern limb today. Measuring more than 200,000 km along its sinuous backbone, the vast structure is in a constant state of motion. NASA's Solar Dynamics Observatory froze it in this snapshot taken 20:16 UT on April 5th:
Filaments as agitated as this one is often erupt and hurl parts of themselves into space. Because of the filament's location on the sun's limb, any such blast would not be Earth-directed, but it would be photogenic! Readers with solar telescopes are encouraged to monitor the action.
more images: from Z. Parsons-West and J. Stetson of South Portland, Maine; from Nicolas SOLDATI of Fribourg, Switzerland; from Peter Desypris of Athens,Greece
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 April 6, 2011 there were 1214 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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