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Sept.
18, 2007: "We've never seen anything quite like
it," says solar physicist Lika Guhathakurta from NASA
headquarters.
Last
week she sat in an audience of nearly two hundred colleagues
at the "Living with a Star" workshop
in Boulder, Colorado, and watched in amazement as Saku Tsuneta
of Japan played a movie of sunspot 10926 breaking through
the turbulent surface of the sun. Before their very eyes an
object as big as a planet materialized, and no one was prepared
for the form it took.
"It
looks like a prehistoric trilobite," said Marc De Rosa,
a scientist from Lockheed Martin's Solar and Astrophysics
Laboratory in Palo Alto, Calif. "To me it seemed more
like cellular mitosis in which duplicated chromosomes self-assemble
into two daughter cells," countered Guhathakurta.
Click
on the image and decide for yourself:
Above:
A magnetic map of emerging sunspot 10926 recorded by Hinode
in Dec. 2006. From beginning to end, the 18
MB time-lapse movie spans 6 days. A shorter 5
MB version is also available. The "trilobite"
centered above is about the size of Earth.
"This
movie is a magnetogram—a dynamic map tracing the sunspot's
intense magnetism," Guhathakurta explains. "Black
represents negative (S) polarity, and white represents positive
(N)."
The
data were gathered by the Japanese Space Agency's Hinode spacecraft,
launched in Sept. 2006 on a mission to study sunspots and
solar storms. "This is the highest resolution magnetogram
ever taken from space," says Tsuneta, Hinode's chief
scientist at the National Astronomical Observatory of Japan
in Tokyo. "It's showing us things
we've never seen before."
(Editor's
note: Additional scientific discussion may be found in the
"more information" box at the end of the story.)
Magnetograms
are the best way to study sunspots. Why? Although sunspots may
appear solid and sturdy, they are not made of matter. Sunspots
are planet-sized knots of magnetism created by the sun's inner
dynamo. Born in the depths, they bob to the solar surface where
they can shift, merge, split and even appear to "swim."
"Sometimes
the shifting and merging gets out of hand," says Guhathakurta.
"Magnetic fields become unstable and explode, producing
a powerful solar flare." The effects are manifold: flares
can disrupt communications on Earth, disable satellites, threaten
astronauts with deadly radiation storms and (on the bright
side) trigger lovely aurora borealis--the Northern Lights.
Although researchers have been studying flares for more than
a century, they still cannot issue accurate flare forecasts--something
astronauts in orbit or en route to the Moon would dearly love
to have. Improving this situation is a key goal of the Hinode
mission.
Participants
at the Living With A Star workshop were amazed by the quality
of Hinode's data. "The sensitivity of Hinode's Solar
Optical Telescope is much higher than anything we've ever
launched before. This allows Hinode to detect even the very
faintest magnetic fields." By
watching the ebb and flow of magnetism and the surprising
forms that emerge, "we hope to understand the behavior
of sunspots and predict their eruptions."
But
first they've got to deal with the trilobites. "We have
a lot of work to do," says Guhathakurta. "But what
a wonderful problem."
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Author: Dr.
Tony Phillips | Production Editor:
Dr. Tony Phillips | Credit: Science@NASA
more
information |
Additional
Discussion:
The
Hinode observations of emergent sunspot 10926 challenge
traditional views of sunspot formation. Before Hinode
data came on line, a solar physicist might have described
the birth of a sunspot as follows:
"Sunspots
are formed when a 'rope' of strong magnetic field beaches
the visible surface of the sun (the photosphere). Magnetic
ropes develop deep below the photosphere and emerge
as an arcade-like structure. When this arcade crosses
the surface a pair of sunspots develops. As in a bar-magnet,
one footpoint of the arcade has positive (northern)
polarity, and the other footpoint has negative (southern)
polarity."
The trilobite data show a different process at work:
"The
emergence of the sunspot magnetism progressed in a very
complex manner, with small pieces appearing to self-assemble
into larger, more coherent structures," says Marc
DeRosa, a scientist from Lockheed Martin Solar and Astrophysics
Laboratory in Palo Alto, Calif.
So
the trilobite movie, while entertaining, is not merely
entertaining. "It has shown us something fundamentally
new" about sunspot genesis, says Lika Guhathakurta.
Credits:
Hinode is a Japanese mission developed,
launched and
operated by ISAS/JAXA, in partnership with NAOJ, NASA
and STFC (UK). Additional operational support is provided
by ESA and NSC (Norway).
Web
links:
NASA's
Hinode home page
National
Astronomical Observatory of Japan -- Hinode Project
page
Japan
Aerospace Exploration Agency -- (JAXA) Learn more
about JAXA's involvement with Hinode.
NASA's
Future: The
Vision for Space Exploration
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