What's inside a star?

Even more incredibly, just by looking at starlight astronomers can discover what a star is made from.The light that we see is just one kind of radiation known as 'visible light'. Other kinds include X-rays, ultraviolet, microwaves, radio waves and infrared. Different stars give out varying amounts of these signals, known as their 'spectrum'.When measured, the spectrum appears as a series of bright and dark lines positioned at specific points or 'frequencies'. This is the blueprint of a star and provides a wealth of information about what is happening inside.As elements are heated inside the star, they absorb and emit energy, creating a 'blip' in the star's spectrum. So the position and strength of these lines reveal what elements are inside the star. Stars are classified into 'spectral types' according to the shape of this spectrum.Find out what happens inside a starLooking back in timeAlthough time travel isn't physically possible yet, we can see back in time just by looking out into space.Light from the Sun takes 8 minutes to reach Earth. So we are seeing what the Sun looked like 8 minutes ago. The faint Proxima Centauri, our nearest stellar neighbour, lags behind by 4.2 years. So, the further we look out into space, the further we are looking into the past.The distance that light travels in a year is called a 'light year'. The furthest that astronomers have ever seen are about 12 billion light years away, from a time just after the Big Bang, when the Universe was just a baby.