The Sun

By: Tori and Caitlin

SHINNING STAR The Sun is the star

at the center of the Solar System. It has a diameter of about 1,392,000 km, about 109 times that of Earth, and its mass accounts for about 99.86% of the total mass of the Solar System.

Composition About three quarters

of the Sun's mass consists of hydrogen, while the rest is mostly helium. Less than 2% consists of heavier elements, including oxygen, carbon, neon, iron, and others.

Characteristics

As the Sun consists of a plasma and is not solid, it rotates faster at its equator than at its poles. This behavior is known as differential rotation, and is caused by convection in the Sun and the movement of mass, due to steep temperature gradients from the core outwards.

Formation The formation of the

Sun may have been triggered by shockwaves from one or more nearby supernovae.This is suggested by a high abundance of heavy elements in the Solar System, such as gold and uranium.

Boundary The Sun does not

have a definite boundary as rocky planets do, and in its outer parts the density of its gases drops exponentially with increasing distance from its center.

The Core The core of the Sun is

considered to extend from the center to about 20-25% of the solar radius. It has a density of up to 150 g/cm3(about 150 times the density of water) and a temperature of close to 13.6 million kelvin (K).

Radiative Zone

From about 0.25 to about 0.7 solar radii, solar material is hot and dense enough that thermal radiation is sufficient to transfer the intense heat of the core outward.

Convective Zone In the Sun's outer layer,

from its surface down to approximately 200,000 km (or 70% of the solar radius), the solar plasma is not dense enough or hot enough to transfer the thermal energy of the interior outward through radiation.

Photosphere The visible surface of

the Sun, the photosphere, is the layer below which the Sun becomes opaque to visible light. The change in opacity is due to the decreasing amount of H ions, which absorb visible light easily.

Atmosphere

The parts of the Sun above the photosphere are referred to collectively as the solar atmosphere. Which is comprised of five principal zones: the temperature minimum, the chromosphere, the transition region, the corona, and the heliosphere.

Magnetic Field The Sun is a

magnetically active star. It supports a strong, changing magnetic field that varies year-to-year and reverses direction about every eleven years around solar maximum.

Summary

The Sun is the star at the center of the Solar System.

About three quarters of the Sun's mass consists of hydrogen.

The formation of the Sun may have been triggered by shockwaves from one or more nearby supernovae.

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"The Sun L  Sun Facts and Images." The Nine Planets Solar System Tour. Web. 11 Jan. 2011. <http://nineplanets.org/sol.html>.

"Sun, Sun Information, Facts, News, Photos -- National Geographic." Science and Space Facts, Science and Space, Human Body, Health, Earth, Human Disease - National Geographic. Web. 11 Jan. 2011. <http://science.nationalgeographic.com/science/space/solar-system/sun-article.html>.

"Sun." Views of the Solar System. Web. 11 Jan. 2011. <http://www.solarviews.com/eng/sun.htm>.