Turn your cell phone into a field-tested satellite tracker. Works for Android and iPhone.
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REENTRY ALERT: NASA reports that UARS, an atmospheric research satllite the size of a small bus, will re-enter Earth's atmosphere on Sept. 23, plus or minus one day. Not all of the spectacularly-disintegrating spacecraft will burn up in the atmosphere; debris could be scattered along a ground track some 500 miles long. Because of the rapid evolution of UARS's decaying orbit, the location of the debris zone is not yet known. A NASA risk assessment places the odds of a human casualty at 1:3200. For last-chance sightings of UARS, check the Simple Satellite Tracker or download the Satellite Flybys app for your smartphone.
SUBSIDING STORM: A coronal mass ejection (CME) hit Earth's magnetic field on Sept 17th, sparking a moderate geomagnetic storm and auroras around the Arctic Circle. The view from Siberia was exquisite:
"I took the picture using my Nikon D3 digital camera," says photographer Ruslan Ahmetsafin of Aykhal, Siberia. "The sky was full of green."
The storm is subsiding now. Nevertheless, high-latitude sky watchers should remain alert for auroras as Earth's magnetic field continues to reverberate from the CME's impact. Aurora alerts: text, voice.
more images: from Michael Kunze flying 30,000 ft over Greenland; from Chad Blakley of Abisko National Park, Sweden; from Joseph Bradley of Whitehorse, Yukon; from B.Art Braafhart of Salla, Finnish-Lapland; from Laffen Jensen of Stjorda, Trondheim, Norway; from John Dean of Dexter, Alaska
UPDATED: September 2011 Aurora Gallery
[previous Septembers: 2010, 2009, 2008, 2007, 2006, 2005, 2004]
GOODBYE SUNSPOT 1289: This weekend, big sunspot AR1289 is approaching the sun's western limb where it will soon disappear from view. Jesús Carmona de Argila of Madrid, Spain, captured these parting shots on Sept. 17th:
The image on the left was taken through an "H-alpha" filter tuned to the red glow of solar hydrogen. It reveals a long magnetic filament trailing the sunspot's dark core. This structure has prompted some observers to nickname AR1289 "the tadpole." The image on the right was taken through a white light filter. It shows the sunspot as the human eye would see it if the sun weren't so blindingly bright. The departing sunspot, while photogenic, poses little threat for Earth-directed flares.
more images: from Jo Dahlmans of Ulestraten The Netherlands; from Gianluca Valentini of Rimini, Italy; from John Chumack of Dayton, Ohio; from Francois Rouviere of Mougins, France; from James Kevin Ty of Manila , Philippines
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 September 18, 2011 there were 1244 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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