20 light years away, the most Earthlike planet yet

[Schneed10]

Originally Posted by FRPLG

I dont get how they decide what the hell this planet is like? Or what anything is rally like that we can't actually really see. Seems like a lot of supposition to me.

It's a bunch of astrophysics stuff. They examine the star and calculate the size. Given that it's a red dwarf, they know the approximate density of it.

They then measure the pattern of fluctuations in the shape of the star, and they can determine that an object of x size orbiting the star would have enough gravity to pull on the star and cause the observed level of fluctuations in the star's shape. They can also calculate the approximate distance from the star that the object would have to be in order to cause the variances in the star's surface.

So they established the size of the object (about as big as Earth), they established that it is orbiting the star, and they've established how far away it is. Now, since they know how much heat a red dwarf star of that size generates, and they know how far away from the star this planet is, they can calculate the expected temperature on this planet's surface. They've determined the temperatures would be earth-like.

We don't have the technology to see something as small as an earth-like planet from 20 light years away. But we can detect and measure the size of stars from that distance. So they just study the star real closely and extrapolate the rest of the information based on the behavior exhibited by the star.