The chemistry behind stars' colours The Orion Nebula. The colour of stars may seem counterintuitive based on our everyday experiences of linking colour to temperature (think colour-coding on taps: red for hot and blue for cold) but it’s the same principle as when metal is heated in a forge.įirst you’ll see it start to glow red, then as its temperature increases the metal glows a blue-white. I say cooler, but bear in mind that the surface temperature of Betelgeuse is still around 3,200✬, compared to Rigel’s 10,700✬. It’s the opposite to what you might think: red stars like Betelgeuse are actually cooler than blue stars like Rigel. The reason stars look different colours - some are red, some are blue - is all to do with their temperatures. Star Betelgeuse is a red giant, while Rigel appears bright blue. Why is this? What causes the different colours of stars? Colour can be seen in the stars of the Orion constellation. Look carefully at the star Betelgeuse – Orion’s right shoulder (assuming he’s facing us) – and you’ll notice that it has an orange-red tinge to it.Ĭompare this with the star Rigel, on Orion’s left foot, and you’ll see that Rigel appears much more blue-white. In the colder months, my favourite sight on a clear night is the familiar Orion constellation, and it’s within this pattern of stars that we can see a classic example of colours in the night sky. Take a quick glance up at the night sky and you can be forgiven for thinking that it only exists in black and white, with distant stars appearing as pinpricks of white light against a dark background.īut next time you're stargazing, look a bit closer and even with the naked eye, you’ll start to see that the Universe is awash with colour.įor more advice, read our guide to astronomy for beginners Red and blue stars captured by the Hubble Space Telescope Credit: ESA/Hubble/ NASA If you've ever noticed this, you might have wondered why. Have you ever noticed that stars have colour? Some stars appear red and some stars are blue.

Color coded periodic table of elements