The Sun The sun is a huge globe

The Sun • The sun is a huge globe of mostly hydrogen (73%), the lightest of the gases. There is also 25% Helium. • It is about 1. 4 million kilometers in diameter (110 times the diameter of the earth). • The sun is so hot (15 000 o. C) that the gas glows and it is this light that speeds through space to reach and warm the earth.

The sun is all “atmosphere” because it is all gas. When people refer to the “surface” of the sun, they are referring to the outside glowing region called the photosphere.

• Some regions on the sun are cooler than their surrounding and therefore appear to be darker. These are known as sun spots. • Near sun spots are where violent solar flares occur. A solar flare is a huge explosion of gas and charged particles. • The solar flares send streams of high energy particles into space. This outflow of particles is known as the solar wind and can have a great affect on the activities of earth.

The Ecliptic • The sun appears to move against the constellations of the celestial sphere. • The path taken by the sun (as it appears to us on earth) across the celestial sphere is called the ecliptic. • This apparent motion of the sun is caused by Earth’s revolution around the sun. The earth’s rotation causes celestial objects to move across the sky from east to west.

The Auroras • The Sun’s corona is constantly releasing charge particles into space. These travelling particles are the solar wind • When particles of solar wind move towards the poles and strike gases in the earth’s atmosphere, a light display is produced (Aurora)