Stars and Galaxies

Stars are enormous balls of glowing gas, like our Sun. They look tiny only because they are incredibly far away from us. Deep inside every star, hydrogen is being squeezed and turned into helium in a process called nuclear fusion — and that is what makes a star shine so brightly.

Why do stars seem to twinkle? It is not the stars themselves — it is our air. As starlight passes through Earth's moving atmosphere, the light gets bent this way and that, making the star appear to shimmer. Above the atmosphere, in space, stars shine with a steady, unblinking light.

Stars come in different colours, and the colour tells us how hot a star is. The hottest stars glow blue-white, medium stars like our Sun shine yellow, and the coolest stars glow red or orange. This is the opposite of what many people expect — blue is hotter than red!