I as a Brad here at ANU and in astronomy we do a lot with light how we discover and what we understand the universe And I'm here with Lish from ABC Canberra and Abby and Caitlin and they're gonna show us how we actually use light in astronomy Yeah, so the white light that we see from the sun and from light bulbs is actually broken up into a lot of different colors that we can't see We can demonstrate that right here with these three torches. We've got the primary colors blue red and yellow Do you hold that Lish and you hold that on Caitlin? So when we shine it on the table we can see that there's three different colors, but when we move it together They create white light. Yeah, so what is something in nature that have a lot of different colors? What does it remind you of a rainbow? Yeah, so a rainbow is like nature's spectrum after a rainfall the water drops in the atmosphere Break up the white light from the sun into a lot of different colors So how can we use a spectra to understand more about space? Yeah, well that's an interesting question. So we attach this instrument which is a spectroscope to our telescopes We look at far away objects like the sun like a star and we can see what they're made of We actually have an example of that here to show you so as you can see here This is actually the spectrum of the sun so you can see the entire rainbow Going down here, but do you notice anything kind of strange about it? Yeah, there's a lot of color, but lots of black lines like a like a grid Yeah, exactly and those black lines are actually because the sun is surrounded by a layer of gas It's called the photosphere. It's a bit like the atmosphere that surrounds our own earth And what happens is when the light leaves the core of the star it actually crashes into that Photosphere the gas surrounding and gets trapped some of the light doesn't make it to earth and those black lines that you tear actually Gats in the spectrum where the light hasn't Got out. It's the light's actually missing what we know is that every element has its own unique pattern of these dark lines So we can analyze this this entire pattern of all the different gases in the photosphere compare them to what we know about the periodic table and Figure out what it's made of so every single animal element has a Spectrum a bit like a I suppose a fingerprint every individual has a finger Exactly so it's a bit like we're looking up if someone's fingerprint in the database and we can see who it belongs to So we can actually look at this as if we were in a lab So here is our gas bowl. It's got some mercury in it have a look through and you can see the spectrum of mercury Yeah, what are you seeing there tell us? Everything is black. I'm like this and I see a line of orange a line of green and a line of that indigo blue Yeah, so that's because there's actually two types of spectrum This is called an emission spectrum. It's where the object in this case mercury emits the light itself And that's different to an absorption spectrum like we talked about with the Sun where the Element whatever happens to be it could be mercury is absorbing and blocking parts of the light So how else can we use this spectra to study astronomy? Yeah, well using the combination of the two different kinds of spectra We can look at so many different things in the universe They can look at nebulae giant clouds of dust and gas and they give of emission spectra We can look at a star which gives us absorption spectra or planets and galaxies which have both you know We can look at the atmosphere of a far away planet See if it might have elements to support life We can look at where stars are born where they die how galaxies move just so many different things So you can really see that spectra is one of the basis of astronomy and it's really the key to making discoveries in space Cool You