The Sun - power house

Live image: click to enlarge.
Source: Hawai'i Institute for Astronomy

Middle Aged

The Sun has existed for 5 billion (5,000,000,000, or 5×10⁹) years. It is one of 150 billion stars in our galaxy, The Milky Way. Despite consuming 5 million tonnes of Hydrogen every second, there is enough material left for it to exist for another 5 billion years.

A Typical Star

Stars can exist with between 1/20 and 70× the mass of our Sun, making it somewhat average. Heavier stars have much shorter lifetimes, since their greater gravity increases the rate of fusion. This also makes them hotter and brighter than our Sun, whose surface temperature is about 6000K. More on stars.

Fusion Perfected

On Earth, humans use Nuclear Fission to produce energy for some of our electricity supply. This is somewhat inefficient, and produces very dangerous nuclear waste. The Sun uses the technically more difficult Nuclear Fusion to produce its energy: 3×10²⁶ joules per second! (3×10²⁶ W).

Fig. 1: Fusion of Hydrogen into Helium

In studying the Sun, we humans have learned how to produce energy from Nuclear Fusion. This century, it may become our main source of energy.

• UK Fusion Programme - excellent graphics
• ITER - International Fusion Project

Revealing Spectrum

Once it was learned that the Sun is just an ordinary star, scientists on earth realised that if we learned about the sun, we were learning about the stars. In the diagram below, the spectrum of the Sun is shown. As you can see, there are lots of unexpected black lines.

Fig. 2: The Solar Spectrum

Spectral Lines

The black lines seen in the solar spectrum are Fraunhofer lines. They indicate the presence of chemical elements in the Sun. Light from other stars is similar - from their spectra we learn about what they're made from. Click for more.

Top Right ^^

Sunspot Revealed!

This photo was taken in 2002 by the Swedish 1-metre solar telescope on La Palma, and is the most detailed picture ever of the Sun's surface. Sunspots are caused by twists in the Sun's magnetic field. A new page will appear here shortly! Source: Institute for Solar Physics, Stokholm

Spectacular Auroras!

SOHO Success

Death of the Solar System

In 1 billion years, the Sun will be bigger and hotter than it is today. The Earth's oceans will have boiled away into space. Stars start to die when they stop burning hydrogen. The sun, a yellow, G-2 star, will (in 5 billion years) then become a red giant encompassing the orbit of Mercury. Mercury will disappear and Venus will lose its atmosphere and become a burnt out planet. The Earth will suffer the same fate, even though it is outside the red giant's immediate reach.

Life Cycles of Stars

An active tale. Check it out!

GCSE Material