Sun.

 
The sun was born from the remains of a nearby supernova. Hydrogen gas swirled and collapsed under its own gravitational force creating incredible pressure and temperatures of well over one million degrees. Such conditions were right for the start of nuclear fusion reactions. Hydrogen began to fuse together and release an incredible amount of energy.

 

 

Our Sun is a type of star known as a yellow dwarf. Yellow because of its colour and dwarf because of its size relative to other stars in our Universe. The word dwarf may not give the right impression of the size of our Sun which can hold one million Earths in its volume.

The Sun produces more energy in one second than was consumed in the entire history of civilisation on Earth.

 

Hydrogen is the fuel used by our Sun. However the reactions that take place are nuclear and give off a great deal of heat. Hydrogen nuclei, under extreme pressure and heat, are fused together to produce helium nuclei. This reaction gives off a great deal of energy.

Each second 600 million tons of hydrogen are fused to form 595 million tons of helium deep in the core of the Sun. The 5 million tons lost in the process is converted into energy, according to the equation E=mc2 which is released into space and powers life on Earth. Click to read a slightly more detailed explanation of this.

 

 

 

The light that we see coming from the Sun has taken a long time, about ten days, to emerge from deep within the core of the Sun. Photons that are released during a nuclear reaction are absorbed and emitted by hydrogen nuclei, in the dense inner core, millions of times, as they make there way to the surface of the Sun. As the photon moves outward from the core through the many layers of the Sun it speeds up as the density of hydrogen atoms becomes less and hence the frequency of its absorption and re-emission also becomes less and less.

 
The photon eventually emerges from the surface of the Sun and along with other highly energised particles takes about 8 minutes to travel 150 million kilometres to Earth. Energy from the Sun powers the weather and is the energy source for life on Earth

 
If light takes 8 minutes to travel to Earth what is its speed in m/s?
Explain what happens to photons that are created in the core of the Sun before leaving the Sun's surface on their journey into space.
What would happen to the Sun if its fuel, hydrogen, was burnt in a conventional manner much like we burn petrol here on Earth?
What conditions need to be present for a nuclear reaction to occur?
What happens during a nuclear fusion reaction?
Is nuclear fission possible in our Sun?

Currently the most accepted scientific theory about the origin of the chemical elements states that the elements hydrogen and helium were created shortly after the Big Bang, about 15 billion years ago. All other elements were created and are still being created in the high pressure and high temperature conditions found within stars.

A particular compound found in our body contains iodine as well as hydrogen, carbon and nitrogen.

The elements in this compound were created
a) in the body.
b) in the cores of stars only.
c) by plants during photosynthesis.
d) from the Big Bang and in the cores of stars and during supernovae.

Sunspots are dark regions that appear on the surface of the Sun..

The graph on the left shows how the average number of sunspots visible on the Sun's surface has varied over time.

a) During which year between 1950 and 2010 was the average number of sunspots highest?

b) According to the trend shown on the graph, when is the next period of peak activity most likely? Click to see a larger image of the graph.
Continue with Iron a deadly astronomical element.
Continue