[ELI5] How can scientists know about the makeup of distant celestial bodies?

Question

I can understand the mass stuff since you can see how they attract/orbit etc, but how can they say stuff like “This planet has a thin atmosphere of 80% sulphur monoxide and 18% helium and it rains nano-diamonds periodically”.

How can you get all this stuff from looking through a telescope?

In: Physics

Answer 1

Like different colored filters for a camera, different materials will reflect/pass different bands of electromagnetic radiation.

By looking at these different reflected (or filtered if they’re passing through the body) waves and comparing them to the source star we can make an educated guess as to what it *might* be made of.