Eli5: how can they tell the composition, mass etc of planets in other solar systems?

Question

For example in they found a planet called “55 Cancri e” which is believed to have a diamond core and its 40 light years away.

Or

A planet called “HD 149026b” which has a temperature of 2,000C and is approximately 250 light years away.

How do they work out this information from so far away?

In: Physics

Answer 1

There are different ways of figuring these out.

For example if they already know the distance / mass of a different star. And this planet passes the star, they can calculate mass through light reduction.

Composition can be detected through the radiation in the air or deduction.

An easy one for example is Earth. We have oxygen so we must have water / carbon. (This works both ways, we have water so we must have oxygen)