The star we see but seldom notice
Summarize the overall properties of the Sun.
What are the different parts of the Sun and how do we know this?
Where does the light we see come from?
Solar activity and magnetic fields.
The Sun is an average star.
From the Sun, we base our understanding of all stars in the Universe.
Like Jovian Planets it’s a giant ball of gas.
No solid surface.
Radius = 100 x Earth (696,000 km)
Mass = 300,000 x Earth (1.99 x 1030 kg)
Surface temp = 5780 K
Core temp = 15,000,000 K
Luminosity = 4 x 1026 Watts
Solar “Day” =
24.9 Earth days (equator)
29.8 Earth days (poles)
How do we know what’s inside the Sun?
Observe the outside.
Theorize what happens on the inside.
Complex computer programs model the theory.
Model predicts what will happen on the outside.
Compare model prediction with observations of the outside.
Continuous monitoring of Sun.
Ground based observatories
One spacecraft (SOHO)
Surface of the Sun is ‘ringing’
Sound waves cross the the solar interior and reflect off of the surface (photosphere).
Core = 20 x density of iron
Surface = 10,000 x less dense than air
Average density = Jupiter
Core = 15,000,000 K
Surface = 5780 K
Everything in the solar system reflects light.
Everything also absorbs light and heats up producing blackbody radiation.
Q: Where does this light come from?
A: The Sun.
But where does the Sun’s light come from?