The Sun, the Earth, and the Evolution of the Earth’s Atmosphere - Air Pollution and Global Warming: History, Science, and Solutions - page 30

Table 2.1. Cosmic abundance of hydrogen relative to those of other elements

Abundance of Abundance of

Atomic H relative Atomic H relative

Element mass to element Element mass to element

Silicon (Si) * Hydrogen (H) 1.01 1:1 28.1 26,000:1

Iron (Fe) *

Helium (He) 4.00 14:1 55.8 29,000:1

Oxygen (O) 16.0 1,400:1 Sulfur (S) 32.1 53,000:1

Carbon (C) 12.0 2,300:1 Argon (Ar) 39.9 260,000:1

Neon (Ne) 20.2 10,000:1 Aluminum (Al) * 27.0 306,000:1

Nitrogen (N) 14.0 11,000:1 Calcium (Ca) * 40.1 413,000:1

Magnesium (Mg)* 24.3 24,000:1 Sodium (Na) * 23.0 433,000:1

Asterisks (*) denote rock-forming elements. All other elements vaporize more readily.
Source :Adapted from Goody (1995).

The sun's interior structure consists of a core, an
intermediate interior (radiative zone), and a hydrogen
convection zone (Figure 2.1). The photosphere, which
is primarily gaseous, is a transition region between the
sun's atmosphere and its interior. Beyond the photo-
sphere, the sun's atmosphere consists of the chromo-
sphere, the corona, and solar wind discharge.
The sun has an effective radius ( R p )of696,000 km,
or 109 times the radius of the Earth (6,378 km). The
sun's effective radius is the distance between the center
of the sun and the top of the photosphere. The mass
of the sun is about 1.99

10 24 kg). The sun's surface
gravity at the top of the photosphere is about 274 m
s − 2 ,or28times that of the Earth (9.8 m s − 2 ).
The sun's core lies between its center and about
0.25 R p .Temperatures in the core reach 15 million
K. At these temperatures, electrons are stripped from
hydrogen atoms. The remaining nuclei (single protons)
collide in intense nuclear fusion reactions ,produc-
ing helium and releasing energy in the form of pho-
tons of radiation that power the sun. Energy from the
core radiates to the intermediate interior ,or radia-
tive zone ,which has a thickness of about 0.61 R p and

mass of the Earth (5.98 ×

×

10 30

kg, or 333,000 times the

Chromosphere
2500 km thick

Photosphere
500 km thick

Hydrogen
convection
zone

Intermediate
interior

0.2 5 R p Corona Solar wind

0.86 R p

Solar radiation

Core

1.0 R p

Figure 2.1. Structure of the sun.