Phil Plait at Slate pointing out the similarities and differences of our planet and Kepler-78b, the “another Earth” exoplanet discovered via space telescope:
“Kepler-78b, it turns out, has a mass of 1.7 times that of the Earth. That may sound like a lot, but remember, Kepler-78b is bigger, too. When you do the math, you find that its density is almost exactly the same as Earth’s!
This means Kepler-78b is most likely made of roughly the same stuff as Earth, and in roughly the same proportion. It may very well have a dense iron core and a lighter rocky mantle just as Earth does.
That’s amazing.
However, the resemblance ends there. With a daytime temperature in the thousands of degrees, the surface of the planet is almost certainly molten rock, so it’s not exactly a vacation spot. But it does show that the Earth is not a one-off planet; the Universe is quite capable of making Earth-sized planets that have the same physical characteristics as well.”
Tags: Phil Plait