iPHONE VS ANDROID! Actually, it doesn't matter which phone you carry. Our cool, new app turns both smartphones into field-tested satellite trackers. Learn more.
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AURORA WATCH: NOAA forecasters estimate a 20% chance of polar geomagnetic activity on Oct 15th when a CME is expected to brush past Earth. High-latitude sky watchers should be alert for auroras.
GREAT FILAMENT: The biggest thing on the sun today is not a sunspot--and it's not even close. A dark magnetic filament 20 times wider than a typical sunspot is meandering across the sun's southern hemisphere. It's so big, astrophotographer Pete Lawrence of Selsey, UK, had to stitch together several pictures to display the entire structure:
The filament is filled with relatively dense plasma held above the stellar surface by magnetic forces. Because this plasma is cooler than the sun below, it appears dark. In fact, it is not. If you could hold the filament out against the black of space, it would glow more brightly than a full Moon.
The 400,000-km scale of the filament--long enough to stretch from Earth to the Moon!--makes it an easy target for safely-filtered backyard optics. If you have a solar telescope, take a look.
more images: from Stephen Ramsden of Immaculate Heart of Mary Catholic School, Atlanta, GA; from Jean-Pierre Brahic of Uzès ( France); from Michael Boschat of Halifax,Nova Scotia,Canada; from James Kevin Ty of Manila , Philippines; from the Solar Dynamics Observatory in Earth orbit; from Didier Favre of Brétigny-sur-Orge, France; from Ron Cottrell of Oro Valley, Arizona;
COMET HARTLEY UPDATE: "Comet 103P/Hartley 2 is growing at an amazing rate," reports Nick Howes of Cherhill, Wiltshire, UK. "The comet's atmosphere (coma) is now more than 1o wide." He took this picture on Oct. 13th using the 2-meter robotic Faulkes North Telescope in Hawaii:
Comet Hartley is approaching Earth for an 11-million-mile close encounter on Oct. 20th. Although it is barely visible to the naked eye, the comet looks great through backyard telescopes. The best time to look is during the dark hours before sunrise when the comet is almost straight overhead in the constellation Perseus. Check Sky & Telescope for a sky map and more.
Need a telescope for Comet Hartley 2? We recommend the David H. Levy Comet Hunter, specifically designed by comet-master David Levy for times like these.
more images: from Rolando Ligustri using a robotic telescope in New Mexico; from Mike Broussard of Maurice, Louisiana; from Fredrik Broms of Kvaløya, Norway; from Tamás Ábrahám of Zsámbék, Hungary; from Efrain Morales Rivera of Aguadilla, Puerto Rico; from P-M Hedén of Vallentuna, Sweden;
October 2010 Aurora Gallery
[previous Octobers: 2009, 2008, 2007, 2006, 2004, 2003, 2002, 2001]
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 October 15, 2010 there were 1149 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 |