How do we know so much about planets that are thousands of not millions of light years away eg their weight, temperature, mass etc
In: Physics
By looking at them. Their color indicates their temperature (blue stars are the hottest, yellow and red are cooler). We can guess their speed by detecting a change in the wavelength they emit, just like a radar speed detector for cars. If the wave length is shifting a lot, it indicates that planets are turning around the star.
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