[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

Each element (hydrogen, nitrogen, helium, etc) have their own “fingerprint” of specific colours, specifically their frequency. By splitting the light that passes through a planet’s atmosphere from the host star, you can identify what elements are present.