From here on Earth, a spot on the Sun is barely a speck on that
bright yellow ball in the sky. But sunspots are huge, bigger than our
planetary home, and they have a complex structure that can’t be seen
without some kind of help. Close up, you’ll see that a sunspot has a
central dark area—called the umbra, which appears dark because it’s
cooler than the rest of the Sun’s surface—with some lighter spots, and
that center is surrounded by a lighter filamentary area, called the
penumbra, that flows outward.
Scientists used the Swedish 1-m Solar Telescope
(which, despite its name, is on the Canary Island of La Palma, off the
coast of Africa) to observe a sunspot near the middle of the Sun on May
23, 2010, and look at how gas flowed in and out; they then used those
observations to create computer simulations of sunspots. Their results
appear this week in Science.
The study supports the idea that sunspots occur as hot gases rise to
the surface of the Sun and spread out, cool and then flow back into the
star. This convective flow creates the pimple-like pattern of a sunspot,
according to the study. And the filaments of the penumbra are actually
columns of gases.
We care about what’s happening with the Sun because our nearest star
can sometimes turn on us, blasting powerful solar storms toward Earth
that “could zap satellites, disable communication networks and GPS
systems and fry power grids at a cost of $1 trillion or more,” Rob Irion
noted in his April story for Smithsonian, “Something New Under the Sun.”
Scientists are using a suite of satellites aimed at the star as well as
telescopes here on Earth to learn more about the Sun. And it’s
increasingly important work: as solar and space physicist Daniel Baker
of the University of Colorado noted in Irion’s story, “The Sun is a
highly variable star…. We live in its outer atmosphere, and the
cyber-electric cocoon that surrounds Earth is subject to its whims. We’d
better come to terms with that.”
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