Sun

Mass (Earth=1)332,800
Mean diameter (106 m)1392
Rotation period26-37 d
Mean distance to Earth, 106 km149
Density (water=1)1.41
Surface gravity m/s2274

Earth's Sun is a medium-sized star which lies on the main sequence with 90% of the known stars. It has a effective surface temperature is 5780 K, putting it in spectral class G2. Its mass is 1.989 x 1030 kg and its mean radius is 6.96 x 108 meters. The mass of the sun is over 99.8% of the mass of the entire known solar system, leading de Pater and Lissauer to refer lightly to the solar system as "the Sun plus some debris".

The sun radiates energy at the rate of 3.85 x1026 watts. Just outside the earth's atmosphere solar energy is received, assuming normal incidence, at the rate of 1340 watts per square meter.

The orbit of Earth ranges from 1.47 to 1.52 x 1011 meters from the Sun. The average light travel time to the earth is 8.3 minutes.

The radius of the sun at 696,000 km is 109 times the Earth's radius. Its surface gravity is 274 m/s2 or 28.0 times that of the Earth. Its mean density is 1410 kg/m3 or 0.255 times the mean density of Earth.

The composition of the sun is 71% hydrogen, 27.1% helium and less than 2% of all other elements.

The center temperature is modeled to be 15.5 million K. The Sun is fueled by the proton cycle of nuclear fusion.

Escape velocity = 618 km/s

Period of rotation averages 25.4 days, varying from 34.4 days at the poles to 25.1 days at the equator (Chaisson). Its axis is tilted 7.25° relative to the ecliptic.

Its apparent magnitude is -26.8 and its absolute magnitude is +4.8 . Its greatest angular diameter as seen from the Earth is 32.5' .

The sun is 7.7 kpc or 25,000 light years from the center of the galaxy and orbits the galaxy in about 200 million years. This corresponds to an orbital velocity of 230 km/s.

Iradiance curve of the Sun
Index

Solar System Illustration

Solar System Concepts

Sun Concepts

References
Chaisson & McMillan
Ch 16

de Pater and Lissauer
Ch 1
 
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