Review

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Review
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Radiation T4
sun
Ideal rT
Degenerate electrons r5/3
r4/3
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For all kinds of gases ideal, degenerate,
whatever
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Combining terms we have
A much more detailed calculation gives 0.08 solar
masses. Protostars lighter than this can never
ignite nuclear reactions. They are known as
brown dwarfs (or planets if the mass is less
than 13 Jupiter masses, or about 0.01 solar
masses.
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14 light years away in the constellation Lepus
orbiting the low mass red star Gliese 229 is the
brown dwarf Gliese 229B. It has a
distance comparable to the orbit of Pluto but a
mass of 20-50 times that of Jupiter.Actually
resolved with the 60 Palomar telescope in 1995
using adaptive optics.
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Spectrum of Gliese 229B
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o
The range of the nuclear force is about 10-13 cm
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pp1
pp2,3
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How much mass burned per second?
How much mass energy does the sun lose each year?
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Now
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k is the opacity (cm2 gm-1)
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Diffusion time for the sun
(less in center, more farther out)
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True even if star is not supported by Prad
Other powers of M possible when k is not a
constant but varies with temperature and density
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Rotation 26.8 d at equator 31.8 d at 75o
latitude
tachyocline
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htpp//www.uni-freiburg.de/pnb/granmovtext1.html
Matter rises in the centers of the granules,
cools then falls down. Typical granule size is
1300 km. Lifetimes are 8-15 minutes. Horizontal
velocities are 1 2 km s-1. The movie is 35
minutes in the life of the sun
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sunspots discovered by Galileo and Harriot 1610
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The cause of the solar cycle is not well
understood, but it is known that the magnetic
field of the sun (or at least its surface field)
goes through reversals every 11 years. The
whole cycle takes 22 years. In the Babcock
model, the cycle is caused by the differential
rotation of the sun. In three years the
equatorial regions go round 5 additional
revolutions compared with the polar ones. This
winds up the field and creates stress that is
released in part by surface activity
(flares, sunspots, etc).
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Caused a mini-ice- age in Europe.
Maunder Minimum
Cause - Multipolar field variation (quadrapole
instead of dipole)? Fluctuations
at tacyocline?
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The smallest loop is 3 times the size of the Earth
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Coronal Mass Ejection
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More details of the solar corona are visible in
the ultraviolet. Picture from the SOHO
observatory in space
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Mass loss rate 10-13 solar masses/yr
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