THE SUN

 

INTRODUCTION

Sun, closest star to Earth. The Sun is a huge mass of hot, glowing gas. The strong gravitational pull of the Sun holds Earth and the other planets in the solar system in orbit. The Sun�s light and heat influence all of the objects in the solar system and allow life to exist on Earth.
 

ROLE IN THE SOLAR SYSTEM

The Sun�s gravitational pull holds the solar system together. The planets, asteroids, comets, and dust that make up our solar system are strongly attracted to the Sun�s huge mass. This gravitational attraction keeps these bodies in orbit around the Sun. The Sun also influences the solar system with its diffuse outer atmosphere, which expands outward in all directions. This expanding atmosphere fills the solar system with a constant flow of tiny, fast, electrically charged particles. This flow is called the solar wind. The region through which the solar wind blows is called the heliosphere. The heliosphere extends outward from the Sun to about 150 times the distance between Earth and the Sun. Interstellar winds may give the heliosphere an egg shape. The solar wind spreads out as it leaves the Sun. The point at which the solar wind is so diffuse that it stops having an effect on its surroundings is called the heliopause. The heliopause marks the outer edge of the solar system.

Within the heliosphere, the Sun provides most of the heat and light that are present, and the particles in the solar wind interact with the planets and satellites in the solar system. The solar wind causes auroras�displays of colored light�in the atmosphere of Earth�s polar regions. The solar wind also carries remnants of the Sun�s magnetic field, which affect the magnetic fields of the planets and larger satellites. The solar wind pushes the planets� magnetic fields away from the Sun, turning them into elongated, windsock shapes.

Microsoft� Encarta� Reference Library 2003. � 1993-2002 Microsoft Corporation. All rights reserved.

 

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