Australian Science Illustrated — Issue 54 2017

The Sun emits light and heat, because atomic nuclei fuse in its interior.

The surplus energy from the process is emitted as light particles.

At the centre of the Sun – from the centre and ¼ of the way

towards the surface – the temperature is up to 15 million

degrees and the pressure so huge that hydrogen atomic

nuclei can fuse. Often, the hydrogen nuclei will just pass by

one another, but sometimes, they fuse to generate energy.

Hydrogen is the most common element of the universe

and also the most simple one, as the nucleus only contains

one proton. In the Sun’s interior, protons collide, resulting

in nuclei from the second most common element in the

universe: helium.

But it's not that simple, when four protons form into a

helium nucleus made up of two protons and two neutrons.

The fusion process requires several stages and is not very

efficient. Luckily, this means that the Sun can burn for a

long time. Our star has been shining for 4.6 billion years

and can burn for another couple of billion years.

Which Processes

Keep the Sun Going?

THE SUN'S CORE

Only at the centre of the

Sun, the temperature

reaches the 10-15 million

degrees required for hydrogen

to fuse with helium.

600,000,000 T

of hydrogen are converted into helium in the Sun's

interior every second. Fortunately, the star's hydrogen

reserves are huge. The Sun weighs about 2 x 10^27 t and will

not run out of hydrogen in its core for another 5 billion years.

Ask Us

SCIENTISTS ANSWER

QUESTIONS FROM

OUR READERS