the sun - east tennessee state universityfaculty.etsu.edu/ignace/astro/astroii_sun.pdf · 2017. 1....
TRANSCRIPT
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The Sun�
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Solar Structure�• Core�• Radiative zone�• Convective zone�• Atmosphere�
– Photosphere�– Chromosphere�– Corona�
• Solar wind (mass loss)�
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Conditions Inside the Sun�
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Solar Power�Sun’s glow fueled by Nuclear Fusion �
– Fusion is a process by which lighter atoms undergo “collisions” that spawn heavier atoms and a release of energy for radiation �
– Fission, on the other hand, is when a heavy atom “breaks up” to yield a lighter atom plus energy�
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Proton-Proton Chain�• p-p chain converts 41H into 14He�"(so 4 bare protons combine to make a helium nucleus with 2p’s and 2n’s)�
• Also get photons and neutrinos in this process�• Neutrinos are (nearly) massless particles
traveling near light speeds and interacting only weakly with matter�
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The Chain�
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Emergence of Light �from the Core �
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Solar Neutrinos�• Neutrinos are elementary
particles moving near light speed, but which interact only weakly with matter.�
• They are important because they can come from nuclear reactions to emerge directly from the core of the Sun.�
• Raymond Davis arranged for the first neutrino experiment. He discovered a “neutrino problem”, but this has now been resolved.�
A modern neutrino experiment, Super-Kamiokande run by Japan
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The Chain�
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Solar Atmosphere�• Photosphere: the layer that we “see” in
visible light �• Chromosphere: tenuous, somewhat
hotter layer above photosphere�• Corona: extended region of million
degree gas above chromosphere extending into space and the solar wind�
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Perspectives of the Sun�
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A Solar Eclipse �
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The Transition Region�
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Solar Activity�• Sunspots – cool blemishes that come and go on
an 11 year cycle�– During cycle, spots initially appear at high latitudes
and thereafter at progressively lower lats.�• Prominences – extended columns of gas that
trace out magnetic loops (can rise to 50,000 km above photosphere)�
• Flares – explosive and energetic events involving hot gas of up to 40 million K�
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Solar Granulation - �Convective Cells�
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Sunspots�
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Spicules �
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The Active Sun�
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Prominences �
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Magnetic Loops at the Sun�
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Solar Cycle in X-rays�
X-ray emission from the solar corona, taken every 120 days, from 1991 (left) to 1995 (going right)
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Solar Cycle in the UV�
Images of the Sun in Extreme UV radiation
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Butterfly Diagram�
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Understanding The Solar Cycle �
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The Solar Cycle in Magnetism�
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Sun-Earth Connection�
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Solar Cycle �and the Earth’s Climate �
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The Solar Wind�• 1951, Biermann discovered solar wind by
considering comet tails�• Speed near earth is around 400 km/s with a
travel time across 1 AU of ~4 days�• Combination of the wind outflow and the
magnetic field have caused a “spin down” of Sun’s rotation over time�
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Solar Wind Mass Flux �
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Space Weather�
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The Resonating Sun�
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Long-Term Changes in the Sun�
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The Sun in Time �
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Solar Sailing: Propulsion in the Future?�
�• To make G > 1 requires a material with �"(A/m) > 1300 m2/kg (equivalent to 36m x 36m)�
• For 1 kg of sail, and G = 2, Fnet = 0.006 N �€
anet = grad − gSun
= (Γ −1)GMo
r2
Γ =Lo
4πGMoc
%
& '
(
) * ⋅
Asailmsail
%
& '
(
) *