THE STAR OF OUR THE STAR OF OUR SOLAR SYSTEMSOLAR SYSTEM

Solar radiation travels from the sun to the earth at the speed of light.

The speed of light is 300 000 km/s.

The sun’s energy does not travel to the earth instantaneously.

It takes about 8 minutes for solar radiation to reach the earth’s surface after leaving the sun.

http://www.youtube.com/watch?v=GmWNs4QrshY http://www.youtube.com/watch?v=GmWNs4QrshY

SUN FACTS

The sun is the only star in our solar system.

• It is 1,000,000 times larger than the earth.

• The sun accounts for 99% of the mass of our

solar system and the planets make up the

other 1% of the mass.

• The planets are tiny specks of matter,

orbiting the Sun due to it’s gravity.

SUN FACTS CONTINUED

• The sun is a big ball of hot gas that

rotates once on its axis every 35 days.

• It is made of 75% hydrogen and 25% helium gas.

• The pressure and temperature of the core is so high that thermonuclear reactions take place. • These reactions produce a large amount of energy.

WHERE IT ALL HAPPENS - THE CORE

• Region where the sun’s energy is first made in a process called nuclear fusion.

• Hottest part of the sun (15,000,000oC).

• What is nuclear fusion?

• It is the process of merging the nucleus of two smaller atoms to create one larger one.

In the core, the sun’s large gravitation force compresses hydrogen atoms together and fuses their nuclei creating helium atoms.

Each second the Sun converts about 600,000,000 tons of hydrogen nuclei into helium nuclei.

The fusion reaction creates an explosion in the core that causes massive amounts of energy to travel from the interior outwards.

1 p+

0 no

e-

1 p+

0 no

e-

2 p+

2 no

e-

e-

Nuclear Fusion

force of gravity

explosion due to nuclear fusion The collapse of the Sun from its own gravity is balanced by the nuclear explosions at its core.

An enormous amount of heat and light moves through several layers or zones toward the outer atmosphere of the sun.

The Sun formed 4.5 billion years ago, and will run out of fuel (hydrogen) in about 5 billion years.

The ratio of hydrogen to helium is changing as nuclear reactions continue to take place.

When this happens, the Sun will explode into a planetary nebula, a giant shell of gas that will destroy the planets in the Solar System (including Earth).

How do we know what elements (e.g.hydrogen and helium) are present in the sun and other stars?

One of the most useful devices that astronomers use to look at light given off by the sun and other stars is a called a spectroscope.

A spectroscope is a device that splits light into a pattern of colours so that we can see them as separate lines of colours.

Works similar to a prism.

Each element that is heated or energized produces its own unique line pattern of colours that can be seen when you look through a spectroscope.