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.
METEOR SHOWER: The Lyrid meteor shower peaks
on April 22nd when Earth passes through a stream of debris
from Comet Thatcher (C/1861 G1). The best time to look is
during the hours before dawn on Thursday morning. Forecasters
expect as many as 20 meteors per hour. [full
IMAGES OF THE SUN: NASA's Solar Dynamics
Observatory is beaming back stunning
new images of the sun, revealing our own star as never
seen before. Even veteran solar physicists say they are amazed
by the data. Click on the prominence, below, to see what everyone
is so excited about:
movies and images!
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,
It is well known that volcanoes
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
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
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.
Northern Lights Gallery
[previous Aprils: 2009,