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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RE-ENTRY UPDATE: NASA has just released new ground tracks for Tuesday morning's scheduled landing of space shuttle Discovery. Once again, US sky watchers are favored. Discovery is expected to pass near or directly above many towns and cities such as Minneapolis, Chicago, Indianapolis, Cincinnati and Jacksonville en route to a 7:34 am EDT landing at the Kennedy Space Center. Using NASA's Skywatch app, you can find re-entry viewing times for your location.
SPACESHIP SIGHTINGS: This morning, space shuttle Discovery and the International Space Station flew over Hombressen, Germany. Astrophotographer Dirk Ewers managed to photograph them booth--"bit it wasn't easy," he said. "With a time difference of only two minutes, I had to swivel my telescope rapidly to catch them both."
But catch them he did, and the result was two clear pictures of the fast-moving spacecraft.
Thanks to bad weather in Florida, Discovery is stuck in orbit for an extra day, so more double sightings are poossible tonight. Check the Simple Satellite Tracker for viewing opportunites or, if you have an iPhone, download the app.
more images: from Ralf Vandebergh of the Netherlands
VOLCANIC LIGHTNING: Iceland's active Eyjafjallajokull volcano is famous for its paralyzing ash, which has grounded thousands of planes in Europe and disrupted travel worldwide. Even more amazing, however, is its white-hot lightning:
"Seeing this lightning crackle among the exploding lava and ash was the experience of a lifetime," says Olivier Vandeginste, who took the picture on April 18th from Hvolsvollur, Iceland.
It is well known that volcanoes produce lightning, but scientists aren't sure why. The underlying mechanism is likely to be some form of triboelectric charging--that is, things bumping or rubbing together (like socks rubbing on carpet) to create a build-up of static electricity. That's how it works in sand storms and even ordinary thunderstorms. In a volcano, the "rubbing things" may be bits of ash and droplets of lava, although no one is certain.
To investigate, a team of researchers from New Mexico Tech has arrived in Iceland to study the phenomenon. Photography is not their primary method, however. Cameras are limited to what they can see through the heavy clouds of ash. Radio receivers can do a better job. Lightning emits impulsive radio bursts which can be measured and counted, day or night, even through clouds of ash. "We are deploying a six-station lightning mapping array around the Eyjafjallajokull volcano," says team member Harald Edens. Their analysis of the radio "crackles" could reveal much about the inner workings of volcanic lightning.
April Northern Lights Gallery
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