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SLIGHTLY LESS QUIET SUN: Solar activity has been upgraded from very low to low. The uptick is caused by the emergence of two new sunspots on the Earthside of the sun. The chance of strong flares from these new active regions remains down around 1%.
NANOSAIL-D FLASHES: NASA's Nanosail-D, the first solar sail to orbit Earth, is flashing. On May 24th, Marco Langbroek watched a high pass over his home in Leiden, the Netherlands. "The sail was easily visible to the naked eye, rapidly flashing with peaks as bright as a first magnitude star," he reports. He photographed the flyby and plotted its variable brightness:
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"At first, the flashes came at an irregular rate of 1 to 3 flashes per second, slowing down (and becoming more regular) to one flash each ~1.6s later," he says. The curious variations suggest that the sail is tumbling. Confirmation comes from other European observers such as Ralf Vandebergh, Russell Eberst, and Bram Dorreman, who have noticed similar flashes from the sail.
Amateur observations of Nanosail-D are of interest to NASA because the agency has never orbited a solar sail before. Everything it does is, by definition, new and interesting. Check the Simple Satellite Tracker or your cell phone for local flyby times--and enjoy the show!
VOLCANIC PLUME OVER NORTH AMERICA: The May 21st eruption of Iceland's Grimsvotn volcano sent a plume of sulfur dioxide into the atmosphere, and today that plume is swirling over the high latitudes of North America. A 5-day movie from the Global Ozone Monitoring Experiment-2 (GOME-2) onboard Europe’s MetOp satellite shows the SO2 in motion:
This is not an especially dense or massive plume. Nevertheless, sky watchers in northern Canada and Alaska should be alert for rare colors and rays in the evening sky. Sulfur dioxide and associated aerosols can produce fantastic sunsets.
April 2011 Aurora Gallery
[previous Aprils: 2010, 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002]
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 May 26, 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. | The official U.S. government space weather bureau |
| The first place to look for information about sundogs, pillars, rainbows and related phenomena. |
| Researchers call it a "Hubble for the sun." SDO is the most advanced solar observatory ever. |
| 3D views of the sun from NASA's Solar and Terrestrial Relations Observatory |
| Realtime and archival images of the Sun from SOHO. |
| from the NOAA Space Environment Center |
| the underlying science of space weather |
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