NEW AND IMPROVED: Turn your iPhone or iPod Touch into a field-tested global satellite tracker. The Satellite Flybys app now works in all countries.
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VOLCANIC SUNSET ALERT: A cloud of ash from the Iceland's Eyjafjallajokull volcano is drifting across Europe today. This has caused a massive disruption in air travel, as many countries have grounded their planes. On the bright side, the cloud is causing sunsets of rare beauty. Europeans should look west at the end of the day. Images: #1, #2, #3, #4.
BONUS: If you don't live in Europe, look west anyway. There's something for you to see, too. Venus, Mercury and the crescent Moon are beaming through the twilight. Sky maps: April 15, 16.
MIDWESTERN FIREBALL: Last night, around 10:05 pm CDT, sky watchers in Minnesota, Wisconsin, Iowa, Illinois and Missouri witnessed a brilliant green fireball streaking across the sky. Images from a rooftop webcam in Madison, Wisconsin, show a brilliant midair explosion:
Credit: University of Wisconsin - AOS/SSEC
The fireball was caused by a small asteroid hitting Earth's atmosphere at a shallow angle. Preliminary infrasound measurements place the energy of the blast at 20 tons of TNT (0.02 kton), with considerable uncertainty. Bill Cooke of NASA's Meteoroid Environment Office estimates that the space rock was about 1 meter wide and massed some 1260 kg. "Fireballs of this size are surprisingly common," he notes. "They hit Earth about 14 times a month, on average, although most go unnoticed because they appear during the day or over unpopulated areas."
Many readers have asked if fragments of the meteoroid might have reached Earth. The answer is yes. Cooke advises looking directly underneath the fireball's debris trail, which was pinged by National Weather Service radars in Iowa. Click here and here for maps.
AURORA WATCH: A solar wind gust hit Earth's magnetic field on April 15th, sparking a G1-class (Kp=5) geomagnetic storm. Skies over Finland lit up with a beautiful mix of green and purple:
"We had a good display for about an hour," says photographer 'JTbo' of Saarijarvi, Finland. "This spring has been something special as the auroras seem to be very strong."
They could become stronger in the nights ahead. A coronal mass ejection (movie) blasted into space by an erupting prominence on April 13th could deliver a glancing blow to Earth's magnetic field on or about April 17th. (Note: This supercedes earlier estimates of an April 15th arrival.) High-latitude sky watchers should remain alert for auroras.
April Northern Lights Gallery
[previous Aprils: 2009, 2008, 2007, 2006, 2005, 2004, 2003, 2002]