| FLYBY ALERT!
Space shuttle Discovery launches on May 31st. Get your flyby
alerts from Space
MARATHON: The 2008 "ISS Marathon"
is underway . For the next two days, the International Space Station
will be in almost constant sunlight. This means sky watchers in
Europe and North America can see the spaceship gliding overhead
as many as four times each night. When should you look? Click
There's a rainstorm underway on the sun's eastern limb. You'd better
bring your asbestos umbrella, though, because the "droplets"
are Texas-sized blobs of hot plasma:
"This is prominence finery at its best," says photographer
Pete Lawrence of Selsey, UK. "Small bright points within the
prominence that were seen on the capture screen have been recorded
as blurs due to the rapid motion of material in just a few seconds!"
Prominences are clouds of hydrogen held above the surface of the
sun by magnetic fields. While this particular cloud appears to be
raining like a summer shower on Earth, the true situation is more
complicated. Look carefully: Some of the plasma raindrops are falling
"up." That's because the motions are controlled by not
only gravity but also magnetism, a force of little importance in
terrestrial rainstorms. The solar magnetic field is rooted below
the sun's visible surface; roiling motions in the body of the sun
itself cause magnetic fields high overhead to shift, wriggle, and
"rain" in all directions. No wonder prominences are so
much fun to watch.
more images: from
Greg Piepol of Rockville, Maryland; from
Stephen Ames of Hodgenville, KY; from
Didier Favre of Brétigny sur Orge, France; from
Malcolm Park of London, England, UK; from
Les Cowley of England;
While most ice haloes we see go around the sun, there is one that
goes right through it: the parhelic
circle. "For a few minutes on the afternoon of May 19th,
cloud conditions were right to form both a 22°
halo around the sun and a perfectly-defined parhelic circle,"
reports Alan Dyer who took the photo, below, from Alberta Canada.
"This produced a sky filled with two intersecting halos--a
"Now is a good time of year to see parhelic circles because
they appear high in the sky," notes atmospheric optics expert
Les Cowley. "The altitude of the circle always matches the
altitude of the sun, hugging
the horizon in winter and rising high
overhead in summer. The higher the sun, the smaller is the circle,
and it can even shrink
smaller than the 22o halo seen crossing it in Dyer's
photo. Almost all types of ice crystal carve the parhelic circle,
it looks very simple but it is made in more
ways than any other halo."
Parhelic circles are pale white like the icy clouds that make them.
"Look carefully to distinguish it from white clouds,"
urges Cowley. "With luck you will see a complete circle."
more images: from
Aymen Ibrahem at the Bibliotheca Alexandrina in Alexandria,
Enzo De Bernardini of Martínez, Buenos Aires, Argentina; from
Stanislaw Rokita of Torun, Poland; from
Marco Candotti of Palmanova, Friuli, Italy;
2008 Aurora Gallery
[Aurora Alerts] [Night-sky