The Sun

NASA photograph, Skylab, 10 December 1973

Sun Facts

• Mass 1.989 × 1030 kg (99.9% of Solar system)• Diameter 1.39 million km (109 times Earth)• Surface Temperature 6000K• Energy Output 3.826 × 1036 W

Spectrum of the Sun

Source: McMath-Pierce Solar Observatories

Layers

Source: Gribbin & Gribbin, From Here to Infinity, 2008, p. 68

Sun’s corona

Source: Koen van Gorp

Density

Source: Arny & Schneider, Explorations, p.314.

Fusion in the Core

Source: Seeds, Horizons: Exploring the Universe

Net reaction: 4 p+ 4He + 2 e+ + 2 + 2

Surface

• Granules– convection cells– Around 1000 km across– Typically last about 10 minutes

Source: NOAO

Sunspots• Relatively cool surface region • Associated with magnetic disruptions

Source: Vacuum Tower Telescope, National Solar Observatory

Sun’s Magnetic Field

• Sun’s interior (plasma) conducts electric current

• Sun rotates: faster at equator than poles

Gas circulation

Source: Solar and Heliospheric Observatory (SOHO)

Solar Cycle

Source: Solar and Heliospheric Observatory (SOHO)

Solar cycle

• Magnetic field reverses every ~11 yr

Source: Gribbin & Gribbin, From Here to Infinity, 2008, p. 72