The Sun

What is the fate of our sun and other stars?

The Sun’s Properties

• 99% of all mass in the solar system• 330,000 times more massive than Earth• Interior Temperature: 10,000,000K• Inner layer: mostly plasma

The Sun’s Atmosphere

• Photosphere– Visible surface of the

sun– 400km thick– Average temp:

5800K– Lowest layer, but

most light

The Sun’s Atmosphere

• Chromosphere– Outside of

photosphere– 2500km thick– 30,000K– Visible during solar

eclipse

The Sun’s Atmosphere

• Corona– Outermost

layer of sun– Low Density– Dim, only

seen in eclipse

– Temp: 1million K – 2million K

Solar Wind

• The corona does not have a true edge

• Gas flows out of the corona at high speeds

• Forms the Solar Wind• Reaches speeds of

400km/s• Causes Auroras

Solar Activity

• Sunspots– Dark spots on surface of

photosphere– Appear darker because

they are cooler– Magnetic Field pokes

through– Hot gases can’t rise

Solar Activity

• Cycles every 22.4 years

• Maximum sunspots every 11.2 years

• Magnetic field reverses

Other Solar Features

• Coronal Holes– Low density– Solar Wind Escapes

• Solar Flares– Eruptions of particles

and radiation

• Prominence– Arc of gas ejected

from chromosphere

Solar Energy

• The sun produces energy largely from Fusion– Fusion – combination of hydrogen atoms to make

helium

• Energy is produced in core of sun• Energy near the core is transported through a

radiation zone (86%)• Near the surface energy is transported

through convection currents