Eli5: How do we know what other planets are like?

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I would like to know how do scientists know what other planets are like billions of light years away from us, i know there are powerful telescopes but even then the planets on the pictures are super tiny

How do they know there is water there or that it has an atmosphere,
Always wanted to ask thanks

In: Physics

3 Answers

Anonymous 0 Comments

There are many different tools scientists have to make estimations about what other planets and stars are like.

We can get an idea for a planet’s mass based on the orbit it has around it’s star, and how far away it is from the star. We can watch how far it orbits and how long it takes and use math to figure out the Mass from there.

If the planet passes between us and it’s star during it’s orbit we can also detect it’s size! We calculate how much light was being blocked from our view when the planet was in between us and it’s star. Kind of like a solar eclipse, but much farther away. We can calculate it’s diameter from that, which leads us to it’s size.

Now that we have size and mass, we can calculate density. This greatly narrows down the possible things the planet could be made of. If it’s a large low density planet, it’s likely a gaseous planet like jupiter. If it’s a high density planet it may have lots of metal.

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