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 diagram above illustrates our solar system. Distances to planets are to scale, the sizes of the planets are not. Credit: www.spaceplace.nasa.gov
On the right is a video of our Sun from NASA’s XXX satellite it shows sun spots rotating into view. The Sun rotates once every 24 days.

The Universe is full of billions of stars, many of which also have planets orbiting around them. These planets are called exoplanets, which means that they are outside of our solar system. Exoplanets are difficult to image directly, because they are small and dim compared with the stars that they orbit. The light from the star overwhelms our detectors, 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 such as: How did our own solar system form? and What are the conditions needed for 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. These small, periodic decreases in light indicate that planets are blocking some of 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 discovering exoplanets much more manageable. However, once there is an initial detection, many exoplanets are better able to be monitored and studied by using telescopes on Earth.


This plot shows the mass of the exoplanet vs. its orbital period around the companion star. There are over 4000 confirmed exoplanets to date, color-coded by the method of discovery.
This plot shows the mass of the exoplanet vs. its orbital period around the companion star. There are over 4000 confirmed exoplanets to date, color-coded by the method of discovery.
Credit: NASA Exoplanet Archive https://exoplanetarchive.ipac.caltech.edu/exoplanetplots/