Other solar systems; Other Earths

Our solar system has one star, the Sun, and many planets including Earth and dwarf planets, which orbit around the Sun.


The Universe is full of billions of stars, many of which also have planets orbiting around them. These planets are called Exoplanets. The word Exoplanet is defined as any planet that is outside of our solar system. The Latin root Exo means outside of and therefore describes a wide range of planets. Exoplanets are difficult to take pictures of directly, because they are small and dim compared with the stars that they orbit. The light from the star overwhelms our cameras, much like trying to take a picture of a bird as it crosses a bright sunlit sky. Learning more about planets around other stars, helps us to answer questions like how did our own solar system form and what kinds of land, air and temperatures might allow life to form and thrive on planets? Even though exoplanets are difficult to image directly, there are many ways to detect planets. NASA’s Kepler and TESS missions carefully measure starlight and detect tiny changes in the amount of light reaching their detectors. Those small, periodic decreases in light indicate that planets are blocking the star’s light as they orbit. Since there are so many stars visible in the night sky, and so many more visible through telescopes, NASA missions make the work of detecting exoplanets for the first time much more manageable. However, once there is an initial detection, some exoplanets are able to be detected, monitored and even better understood over time by simpler telescopes on Earth.