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By BBC News Online science editor Dr David Whitehouse
Scientists are currently observing
the largest sunspot seen on the surface of our star for
more than a decade.
Researchers
think it could lead to a powerful flare some time in the
next day or so. If this explosive event does occur, it will
liberate in just a few seconds more energy than mankind
has ever used.
The
sunspot group, designated Noaa 9393, was first seen a month
ago when it was not nearly so large.
The
Sun's rotation took it from view but when it reappeared
a few days ago astronomers were amazed that it had grown
so big.
Over
the past 24 hours it has become unstable displaying signs
that its pent-up energy is about to be explosively released.
Monster
spot
The
sunspot is a monster according to Joe Elrod of the US National
Solar Observatory at Sacramento, California: "This
is the first big one we have seen during this solar cycle,"
he told BBC News Online.
Noaa 9393: Bigger than the Earth
Every
11 years or so the Sun goes through a peak of activity when
there are more sunspots on its surface. Solar observers
say that 2001 is the year of the current peak.
Noaa
9393 is so large that it is even visible to the unaided
eye, though astronomers say that under no circumstances
should anyone without proper protective equipment ever look
towards the our star as blindness can result.
Sunspots
are regions of the Sun's surface that are marginally cooler
than their surroundings. They only appear dark by contrast.
If they were alone they would shine brighter than an arc
lamp.
The
'big one'
They
are caused when intense magnetic fields rise up from below
the Sun's visible surface. They then become twisted and
distorted by surface motions storing up vast amounts of
magnetic energy.
Eventually,
the magnetic energy becomes unstable and collapses, resulting
in the explosive heating of vast amounts of gas. This is
when solar flares are produced.
The
most intense solar flares are called "white light"
flares and it is this type of event that sunspot group Noaa
9393 is expected to produce.
"We
saw two small flares yesterday, and they may be the precursors
to the big one," Joe Elrod said.
Scientists
say that the Sun is currently going through a particularly
active phase with many groups of sunspots on its surface.
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