Encyclopedia of the Solar System 2nd ed

72 Encyclopedia of the Solar System

TABLE 1 Basic Physical Properties of the Sun

Physical Parameter Numerical Value

Solar radius,R 695,500 km

Solar mass,m 1.989× 1033 g

Mean density,ρ 1.409 g cm−^3

Gravity at solar surface,g 274.0 m s−^2

Escape velocity at solar surface,v 617.7 km s−^1

Synodic rotation period,PP= 27 .3 days (equator)

Sidereal rotation period,PP= 25 .4 days (equator)

P= 35 .0 days (at latitude± 70 ◦)

Mean distance from Earth 1 AU=149,597,870 km

Solar luminosity,L 3.844× 1026 W (or 10^33 ergs s−^1 )

Solar age,t 4.57× 109 years

Temperature at Sun center,Tc 15.7× 106 K

Temperature at solar surface,Tph 6400 K

Source: Cox, 2000.

FIGURE 1 A cutaway view of the Sun, showing the three internal (thermonuclear, radiative, and
convective) zones, the solar surface (photosphere), the lower (chromosphere) and upper
atmosphere (corona), and a number of phenomena associated with the solar activity cycle
(filaments, prominences, flares). (Courtesy of Calvin J. Hamilton and NASA/ESA.)