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VENUS HAS A SIDEKICK:
Look east just before dawn on Sunday morning,
Sept. 20th. There's Venus, as usual, shining through the rosy glow
of sunrise. A pair of binoculars trained on Venus reveals a temporary
sidekick: 1st-magnitude star Regulus less than 0.5o away.
Don't miss it: sky
map.
APPROACHING SUNSPOT:
NASA's STEREO-B spacecraft stationed over
the sun's eastern limb is monitoring an active region not yet visible
from Earth. STEREO's extreme ultraviolet telescope captured this
image on Sept. 19th:
The tangle of hot, magnetized plasma circled above almost certainly
overlies a large new-cycle sunspot. We'll soon find out. The sun's
rotation is turning the active region toward Earth and it could
pop over the sun's eastern limb as early as Sept. 21st. Readers
with solar
telescopes are encouraged to monitor developments.
FOGBOW SEASON:
Northern autumn is beginning and that means it's fogbow
season. The weeks of late September and early October often bring
banks of fog to the countryside, where moist ground has spent the
night cooling under a cloudless, starry sky. When the sun comes
up, warms the ground, and sunlight hits the rising mist--voila!--a
fogbow:
Claude Duplessis took the picture at daybreak on Sept.
17th. "I spent the night in La Vérendrye Wildlife Reserve in
Québec," he says. "In the morning, as I prepared to leave,
this white 'bow popped out of the mist."
Fogbows are close cousins of rainbows. The difference
is droplet size. Rainbows appear when sunlight bounces
in and out of large raindrops. The same type of reflection produces
a fogbow, except fog droplets are much smaller. Small droplets
don't separate the colors of sunlight as widely as large raindrops
do. In a fogbow, therefore, the colors are smeared together, producing
a ghostly-white arc.
To see a fogbow on a misty autumn morning, face away
from the rising sun and look into the fog. The lower the sun, the
higher the arc, so wake up early for best results!
more images: from
Daryl Pederson of Prince William Sound, Alaska; from
Tyler Burg of Pisgah, Iowa; from
Ákos Ujj of Bátonyterenye, Hungary;
Sept.
2009 Aurora Gallery
[previous Septembers: 2008,
2007,
2006, 2005,
2004, 2002,
2001]
Explore
the Sunspot Cycle |
