Download The Photosphere

‫‪Chapter 7‬‬
‫‪The Structure and the‬‬
‫‪Origin of the Solar‬‬
‫‪System‬‬
‫والشمس وضحاها‬
‫والشمس تجري لمستقر لها ذلك تقدير العزيز العليم‬
‫ومن آياته الليل والنهار والشمس والقمر‬
Sun
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The Sun is our nearest star.
4 light years for the next nearest star.
diameter: 1,390,000 km. (1 million VE)
mass: 1.989e30 kg (331500 ME)
temperature: 5800 K (surface) 15,600,000
K (core)
Revolution of the Sun
• the Sun's orbit around the center of the
Milky Way once every 225 million years.
• The period of time is called a cosmic
year.
• The Sun has orbited the galaxy, more than
20 times during its 4.5 billion year lifetime.
Rotation of the Sun
• The sun as a whole has no single period
of rotation, but different portions of its
surface perform their revolutions in
different times.
• At higher latitudes the sun tends to rotate
more slowly.
• It is estimated that the sun’s period of
rotation at the surface varies from about
25 days at the equator to about 35 days at
the poles.
The center of the Sun
• very hot (about 15 million degrees Celsius) and the
pressure is immense (about 100 billion times the
airpressure here on Earth).
The center of the Sun
• In every second, the Sun spends 700
billion tons of protons (or: Hydrogen) in
this way. And only a small fraction (0.7
percent) is turned into light.
• Right now, about half of the amount of
Hydrogen in the core of the Sun has been
fused into Helium. This took the sun about
4,5 billion years.
The surface of the Sun - The
Photosphere
• The photosphere is the
thing you see when you
look at the sun .
• Each square centimeter of
the solar surface emits as
much light as a 6000 Watt
lamp.
The surface of the Sun
The Photosphere
• Solar spots are areas on the Sun where
the magnetic field is much higher than
elsewhere. This increases the `magnetic
pressure', which in turn decreases the
normal atmospheric pressure. And
because of that, the temperature in the
solar spots is lower than in the
surrounding area.
Solar Spots
• The number of spots
on the Sun isn't
constant, but varies
with a period of 11
years, called the solar
cycle.
Solar Spots
The atmosphere of the Sun - the
Corona
• The corona begins at the top of the
atmosphere.
• Because the corona is so thin, you can only see
it during a solar eclipse.
• Extends outward from the surface several
million miles or kilometers .
• . The temperature of the corona averages 2
million degrees Kelvin;
Video, Video2
Phases of the Moon
• Waxing" means
growing
• "waning" means
shrinking.
• "gibbous" :"swollen
on one side."
• Period 29.5 (
13 hours)
• 50 min late
every night.
Lunar Motion