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.
|
