Sun Fact Sheet

Sun/Earth Comparison

Bulk parameters

	Sun	Earth	Ratio (Sun/Earth)
Mass (10²⁴ kg)	1,988,400.	5.9722	332,900.
GM (x 10⁶ km³/s²)	132,712.	0.39860	332,900.
Volume (10¹² km³)	1,412,000.	1.083	1,304,000.
Volumetric mean radius (km)	695,700.	6371.	109.2
Mean density (kg/m³)	1408.	5514.	0.255
Surface gravity (eq.) (m/s²)	274.0	9.78	28.0
Escape velocity (km/s)	617.6	11.19	55.2
Ellipticity	0.00005	0.0034	0.015
Moment of inertia (I/MR²)	0.070	0.3308	0.212
Visual magnitude V(1,0)	-26.74	-3.86	-
Absolute magnitude	+4.83
Luminosity (10²⁴ J/s)	382.8
Mass conversion rate (10⁶ kg/s)	4260.
Mean energy production (10^-3 J/kg s)	0.1925
Surface emission (10⁶ J/m²s)	62.94
Spectral type	G2 V

Model values at center of Sun:

Central pressure: 2.477 x 10¹¹ bar (2.477 x 10¹⁷ g/cm s²) Central temperature: 1.571 x 10⁷ K Central density: 1.622 x 10⁵ kg/m³ (1.622 x 10² g/cm³)

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	23.44	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

North Pole of Rotation

Right Ascension: 286.13
Declination    :  63.87
Reference Date : 1.5 Jan 2000 (JD 2451545.0)

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 
Pressure at bottom of photosphere (optical depth = 1): 125 mb
Effective temperature: 5772 K
Temperature at top of photosphere:  4400 K
Temperature at bottom of photosphere:  6600 K
Temperature at top of chromosphere:  ~30,000 K
Photosphere thickness:  ~500 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

Notes on the factsheets - definitions of parameters, units, notes on sub- and superscripts, etc.

Directory to other Planetary Fact Sheets

Author/Curator:
Dr. David R. Williams, dave.williams@nasa.gov
NSSDCA, Mail Code 690.1
NASA Goddard Space Flight Center
Greenbelt, MD 20771
+1-301-286-1258