our only contact with the distant stars is their lights that's journeyed across the universe to reach us and
Encoded in that light is the key to understanding what the universe is made of and it's all down to a particular property
Of the chemical elements you see when you heat the elements when you burn them then they give off light
And each element gives up its own unique set colors
So this strontium and it burns
with a beautiful red color
sodium is yellow
Potassium is lila and Copper is blue
Each element has [its] own characteristic color
it's this property that tells us what the stars are made of
But it's a little more complicated than simply looking at the color of the light that each star emits
You can see why by looking at the light [from] our nearest star the sun?
This is a spectrum of the light taken from our sun, and you know at first glance. It looks very familiar
it looks like a stretched out rainbow because that's [exactly] what a rainbow is is the
spectrum of the light from the Sun in the sky
But if you look a bit more closely, then you see that this spectrum is covered in Black Lines
These are called absorption Lines
Each element within our sun that only emits light at a certain color it also absorbs light at the same color
By looking for these black lines in the sun's light. We can simply read off a list of its constituent elements like a barcode
For example these [two] black lines in the yellow bit of the spectrum
sodium you can see
Iron
right down here
You can see hydrogen so by looking at these lines in precise detail you can work out exactly
What elements are present in the sun and it turns out that that's about 70% hydrogen
28% helium and
2% the rest and you can do this not only for [the] sun
But for any of the stars you can see in the sky and you can measure
exactly, what it made of
so
That star there is Polaris [pulstar]
and you can see that because all the other stars in the night sky [theater] rotate around it now it's
[430] [Light] [Years] away
But we know just by [looking] at the light that it has about [the] same heavy element abundance as our sun
But it's got markedly less carbon and a lot more nitrogen
and the same applies for other stars
Vega [the] second brightest star in the Northern sky has only about 1/3 of the metal content of our sun
Whereas other stars and metal heavy
Sirius the dog star contains three times as much iron as the sun
And Proxima Centauri is rich in magnesium
But although the quantities of the elements may vary wherever we look across space
We only ever [find] the same 92 elements that we find on Earth