1. The Sun

2. The Sun Our closest star (a yellow dwarf)
Source of all energy on Earth
Located 149 million km from Earth
or 1 AU (Astronomical Units)
Light takes a million years to get from the core to the Sun’s surface but only 8 minutes to reach us

3. The Sun Rotates on its axis and orbits the galaxy, same as us
About half way through its 10 billion year life cycle
Sun will swell into a red giant, then cool to form a brown or black dwarf

4. The Sun

5. The Core
25% of its radius
Intense pressure causes nuclear fusion – atoms of hydrogen fuse to form helium
Gives off huge amounts of energy (a billion 1 Mt nuclear blasts per second)

6. The Interior Radiative Zone 45% of Sun’s radius
Energy carried out by photons (light energy)
Takes huge amount of time to get through

7. The Interior Convective Zone 30% of Sun’s radius Waves of hot gas
Carry energy outward to surface

8. The Atmosphere
Made up of 3 parts: the photosphere, the chromosphere, and the corona

9. The Atmosphere Photosphere The surface of the Sun 300 – 400 km wide
6000˚ Celsius

10. The Atmosphere Chromosphere Above photosphere (about 2000 km)
Convection currents cause temp. to rise to 10000˚ Celsius

11. The Atmosphere Corona Extend millions of km out in space
Best seen during a solar eclipse or X-ray of the Sun
About ˚C – perhaps due to Sun’s magnetism

12. Solar X-Ray
Photosphere
Chromosphere
Corona

13. Other Features Sunspots Darker, cooler regions on the surface
Intense magnetic field
Runs in an 11 year cycle (2010 is when sunspots are at a minimum)

14. Other Features Prominences Solar Flares
Clouds of gas from the chromosphere
Rise up along magnetic lines from sunspots
Solar Flares
Violent eruptions from the Sun
Release intense radiation which cause auroras (Northern Lights)

15. Life of a Star The fate of a star depends on its size Dwarf Stars
Like our sun, will swell up (red giant) then slowly burn out (white dwarf then black dwarf)
Will take several billion years

16. Fate of the Sun

17. Life of a Star Huge or Giant Stars
Will become a supergiant, then explode into a supernova (core instantly collapses)
Eventually ends up as a neutron star or a black hole

19. Neutron Star 1.5 – 3 times mass of Sun
Core shrinks to diameter of 10 km, mass still double the Sun
Huge magnetic field and rapid spin

20. Black Hole > 3 times mass of Sun Contracts tremendously
Gravitation pull so strong not even light can escape!