Today, the solar prominence count is seven.
The largest one is a gorgeous arch shown
here in a photo from amateur astronomer James Screech of Bedford,
England. "I took the picture using my Personal
Solar Telescope," he says. For scale, a pair of planet
Earth's could fit through the enormous loop with room to spare.
Sunspot 1016 has vanished. Yesterday it rotated over the western
limb of the sun where it can no longer be seen from Earth. But has
it really vanished? According to NASA's STEREO-A
spacecraft, the sunspot still exists. It is circled in this extreme
UV image just beamed back to Earth:
STEREO-A is stationed
above the western limb of the sun. From that vantage point, the
spacecraft can track sunspots for days after they leave the range
of terrestrial telescopes. Back on Earth, the sunspot number has
dropped to zero, but STEREO-A is still counting.
So is the sun blank--or not? For more than 200 years,
astronomers have counted spots on the Earth-facing side of the sun
and called that the sunspot number. Farside spots couldn't be seen
and didn't count. Continuing this tradition makes sense because
it allows us to compare data across the centuries. So, today, the
sun is officially
blank even if STEREO-A knows better.
In Cape Elizabeth, Maine, the last sunrise of April was a doozy.
Standing on the shore of Casco Bay on April 30th, photographer John
Stetson captured this sequence of images:
"Our sun can appear in interesting shapes," says Stetson
with understatement. "This is a result of Earth's atmosphere
acting as a lens to refract the light that we see."
Atmospheric optics expert Les Cowley elaborates: "In John’s
sequence the solar image struggles upwards through multiple atmospheric
inversion layers. Each has unusually cooler air trapped beneath
warmer, and each splits the sun’s light into two
images – one rising, one inverted and sinking. Where they overlap
we see a bulging 'spare tire'! Such mirages are the stuff of a special
type of green
flash, a 'mock-mirage'
that is frequently photographed but is very rarely seen with the
A close-up look
at the distorted sun reveals even more: "John has caught several
instances of the green upper rim flash and lower 'red flashes' where
the last fragment of an image caught between inversion layers is
reddened and vertically stretched."
What kind of sunrises will May bring? Stay tuned.
2009 Aurora Gallery
[previous Aprils: 2008,
the Sunspot Cycle