The SUN!

Basic Facts

• Mass M = 2x1030 kg = 300,000ME

• Radius R = 7x108 m = 7x105 km = 111RE

• Mean Density = Mass/Volume = M/((4/3)R3)= 1400 kg/m3 = 1.4 g/cm3

• Distance = 1.5x1011 m = 1.5x108 km = 8.3 light-minutes

• Luminosity L = 3.9x1026 W (Solar Constant = 1350 W/m2)

• Mean Surface Temperature = Teffective = 5780 K

• Composition By Mass By Number

• H ~68%~90%

• He ~31%~10%

• “Heavies” ~1% ~1%

The Sun Contains 99.8% of the Mass of the Entire Solar System!

We Rely on the Sun for…

…

• Source of energy• Plants-photosynthesis• Creates wind• Water cycle

The Sun’s Atmosphere

Photosphere

• All elements are gaseous • Get denser as you move toward the core• Photosphere is the “surface” we can see

Granulation

Chromosphere

• Density decreases but temperature increases• Oddity considering the rest of the sun

decreases in temperature as you move away from the core

Spicules

• Flamelike jets of gas that rise up into the chromosphere

The Corona

• Outermost part of the Sun’s atmosphere• Extends millions of miles into space

Reading

Solar Activity

Magnetic Field

Video

• http://www.usatoday.com/story/news/nation-now/2014/01/06/sun-magnetic-field-polarity-reverse/4306845/

Sunspots

• What are they?– Regions marked by lower temperatures– Dark spots on the solar surface

• Cause– Magnetic field exits one and enters the other– Messes up convection in granules and causes

cooling

Structure

• Umbra-dark region• Penumbra-lighter surrounding region

History

• 1610 Sunspots were first observed by Johannes and Fabricius

• 1612 Galileo explained sunspots

How They Are Used

• Rotation of the Sun• Weather?– Low sunspot activity– High sunspot activity

Little Ice Age

• Low solar activity-few sunspots • 1645-1715• Frozen rivers and year-round snow in unlikely

places

Sunspot Cycles

• Cycles every 11 years

Maunder Minimum

• Lowest point of solar activity

Prominences

• Magnetic field redirects the flow of the gases-out one and in the other

Coronal Mass Ejection

• http://csep10.phys.utk.edu/astr162/lect/sun/comet.mpg

• Causes on Earth

Solar Winds

• Flow of charged particles away from the sun• Continual• Greater at coronal holes and less at helmet

streamers

Fusion

• http://www.youtube.com/watch?v=pusKlK1L5To