Other Worlds, Other Stars
We used to be able to count the number of known planets on the ﬁngers of both hands. Then astronomers developed ways to ﬁnd worlds around other stars. We are discovering new ones all the time, as shown on the counter above. Our solar system isn’ t alone in the galaxy anymore.
We haven’t found a planetary system that exactly matches our Sun’s collection of planets, moons, asteroids, and comets. The ﬁrst extrasolar worlds we discovered are the size of Jupiter. The search continues for even smaller, more Earthlike planets orbiting other stars.