What are standard candles?

Standard candles are tools scientists use to measure how far away things are in space, just like a real candle helps you see how bright something is.

Imagine you have two identical flashlights. One is right next to you, and the other is across the room. The one that's farther away looks dimmer, even though both are the same brightness. That’s because light spreads out as it travels, the farther it goes, the less bright it seems.

Standard candles work in a similar way. They’re objects we know how bright they really are, like a flashlight we’ve tested before. When scientists look at these objects from far away, they can tell how far they are based on how dim they appear. If something looks dimmer than expected, it must be farther away!

Scientists use standard candles to measure the distance to stars and even galaxies. One common type is a supernova, which is like a really bright explosion from a star. Because we know how bright these explosions are when they happen, scientists can figure out how far away the stars are, just like you can tell how far away your flashlight is by how bright it looks!