Ever wonder how astronomers know the composition of distant stars, galaxies and nebulas? It's easily done by breaking down the light from these distant objects using a prism. Different elements produce different sprectra, so star light can be broken down too.
Here is a video that explains how we know the composition of every star and galaxy at which we can point a telescope.
Here is a great video from Dr. Brian Cox from BBC who explains how different elements give off different light spectra and absorption spectra. It is the dark bands of absorption spectra that are the codes for the elements being fused in each star.
By interpreting light sprectra from all the stars in the sky, astronomers have determined that they all contain the same 92 elements found on Earth!
In other words, we are all made of the same "Star Stuff". This links the Earth and all life as we know it, to the rest of the universe.
Astronomers can also use light spectra to determine a star's temperature, distance, composition and they can tell if it is moving away from Earth or moving towards us.
This is light physics at its best.
Maddalena Environmental Inc.