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With hundreds of billions of stars in each of the
universe's hundreds of billions of galaxies, you'd
think astronomers had plenty to study. And, of course,
they do. Using telescopes and satellites they can
measure the color, location, and changes in luminosity
of 200 billion stars within the Milky Way alone. The
problem, however, is they can see only one of these
-- the Sun -- up close. Even then, they can't look
below its photosphere -- the light-emitting outer
layer.
Since astronomers can neither zoom in on more distant
stars nor peek under the cover of even the nearest
one, how do they learn what happens deep inside these
stellar furnaces? If they are Paul Woodward and David
Porter, they create their own.
These Alliance astrophysicists, nearly as well known
for setting computing records as for analyzing stellar
fluid dynamics, recently got up close to a red giant
-- a star many times larger than the Sun. Along with
other members of the Laboratory for
Computational Science and Engineering (LCSE) at
the University of Minnesota, they generated a 3D
simulation of a red giant at NCSA with such detail
that they could watch it pulsate.
One of the things they saw was a region of superhot
gasses in turmoil like a pool of lava that encompassed
nearly the entire star -- a region equivalent to the
orbital radius of Jupiter around the Sun. What's more,
this "global convective pattern" flowed
asymmetrically. Gas flowed outward from the center of
the generally hotter side of the star and around to
the cool side, giving off heat along the way. Once on
the cool side, the gas sank, forming a funnel that
reheats upon passing the hot, stellar core.
If further analyses confirm this pattern, it may
explain differences in illumination within these big,
pulsating stars -- a finding that is important to
astronomers who rely on these "standard candles" for
mapping distances in the universe. It will also help
scientists know what to expect from our own Sun
because eventually it, too, will become a red giant.
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