STAR SORT
Stars come down the chute and you sort them by colour. Blue ones are the hottest, red ones the coolest — which is the opposite of every tap you have ever used.
What this machine is actually teaching
A star’s colour is a thermometer. Blue is hot — around 30,000°C. Red is cool — around 3,000°C. Our Sun sits in the middle at about 5,500°C and reads yellow-white.
That feels backwards, because red taps and red buttons mean hot to us. But it is true of anything glowing: heat a piece of iron and it goes red, then orange, then white, then blue-white. Astronomers use exactly this to know a star’s temperature from light that left it thousands of years ago.
The classes have names, in order from hottest to coolest: O B A F G K M. Generations of astronomers have remembered them with a silly sentence. Make up your own.