Sun Fact Sheet

Sun/Earth Comparison

Bulk parameters

                                     Sun          Earth      Ratio (Sun/Earth)
Mass (10²⁴ kg)                     1,989,100.      5.9736      332,950.    
GM (x 10⁶ km³/s²)                    132,712.      0.3986      332,950.  
Volume (10¹² km³)                  1,412,000.      1.083     1,304,000. 
Volumetric mean radius (km)         696,000.       6371.      109.2
Mean density (kg/m³)                1408.          5520.        0.255       
Surface gravity (eq.) (m/s²)         274.0         9.78        28.0     
Escape velocity (km/s)               617.7        11.2         55.2     
Ellipticity                         0.00005        0.0034       0.015
Moment of inertia (I/MR²)              0.059       0.3308       0.178      
Visual magnitude V(1,0)              -26.74       -3.86          -  
Absolute magnitude                    +4.83
Luminosity (10²⁴ J/s)                384.6
Mass conversion rate (10⁶ kg/s)     4300.         
Mean energy production (10^-3 J/kg)     0.1937
Surface emission (10⁶ J/m²s)          63.29
Spectral type                         G2 V

Model values at center of Sun:
Central pressure:     2.477 x 10¹¹ bar                 
Central temperature:  1.571 x 10⁷ K
Central density:      1.622 x 10⁵ kg/m³

Rotational and Orbital parameters

                                          Sun        Earth      Ratio (Sun/Earth)
Sidereal rotation period (hrs)*         609.12       23.9345     25.449     
Obliquity to ecliptic (deg.)              7.25       23.45        0.309
Speed relative to nearby stars (km/s)    19.4

*This is the adopted period at 16 deg. latitude - the actual rotation rate varies with latitude L as:
( 14.37 - 2.33 sin² L - 1.56 sin⁴ L ) deg/day

Sun Observational Parameters

Apparent diameter from Earth
        At 1 A.U.(seconds of arc)  1919.
        Maximum (seconds of arc)   1952.
        Minimum (seconds of arc)   1887.
Distance from Earth
        Mean (10⁶ km)              149.6
        Minimum (10⁶ km)           147.1
        Maximum (10⁶ km)           152.1

Solar Magnetic Field

Typical magnetic field strengths for various parts of the Sun 

Polar Field:  1 - 2 Gauss 
Sunspots:  3000 Gauss
Prominences:  10 - 100 Gauss
Chromospheric plages:  200 Gauss
Bright chromospheric network:  25 Gauss
Ephemeral (unipolar) active regions:  20 Gauss

Solar Atmosphere

Surface Gas Pressure (top of photosphere): 0.868 mb  
Effective temperature: 5778 K
Temperature at bottom of photosphere:  6600 K
Temperature at top of photosphere:  4400 K
Temperature at top of chromosphere:  ~30,000 K
Photosphere thickness:  ~400 km
Chromosphere thickness:  ~2500 km
Sun Spot Cycle:  11.4 yr.

Photosphere Composition: 
    Major elements: H - 90.965%, He - 8.889%
    Minor elements (ppm): O - 774, C - 330, Ne - 112, N - 102
			  Fe - 43, Mg - 35, Si - 32, S - 15

Questions and comments about this page should be addressed to:
Dr. David R. Williams, dwilliam@nssdc.gsfc.nasa.gov, (301) 286-1258
NSSDC, Mail Code 633, NASA/Goddard Space Flight Center, Greenbelt, MD 20771