system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How do scientists determine the possible habitability of exoplanets?

With the search for possible Earth analogs in our universe going on still, how to scientists determine whether or not a planet is habitable even tho often times they can't physically see the planet?
gpt
They can tell how bright the star is fairly easily. From this information they can determine how much energy the star is putting out. Then, they look at how fast the planet is orbiting around its star by measuring how often the planet causes the star's light to dim or wobble. From information about how fast the planet is orbiting they can determine how close it is to its host star.

Now that they have the energy output of the star they can determine if the planet is in the range where water can be liquid. If the planet is too close then all water will evaporate but if it's too far then the water will all freeze.