Exoplanets have been found in a relatively small region of our galaxy, the Milky Way. According to NASA's Kepler Space Telescope, there are more planets in the universe than stars.
Our solar system's exoplanets comprise similar elements to our planets, but their mixtures may differ. By measuring the sizes (diameters) and masses (weights) of exoplanets, we can determine their compositions, which range from very rocky (like Earth and Venus) to very...