Standard candle

A standard candle is something that scientists use to measure how far away things are in space. You know when you blow out a birthday candle and it gets really tiny and starts to fade away? That's because the flame is getting smaller and smaller until it finally goes out completely.

Well, standard candles are kind of like really, really big versions of birthday candles. They are special types of stars that always give off the same amount of light. Scientists can use this to figure out how far away things are in space.

It's just like how you can tell how far away a car is by how loud it sounds. If you know how loud something is when it's really close to you, you can figure out how far away it is when it gets quieter. With standard candles, the scientists know how bright they are when they're really close, so they can figure out how far away they are by how bright they look from far away.

So basically, when scientists find a star that's a standard candle, they can use it to measure how far away other things are in space by comparing their brightness to the brightness of the standard candle. Cool, huh?