The Largest Rock Known
There, that faint dot in the center - that's the largest rock known. It is larger than every known asteroid , moon , and comet nucleus . It is larger than any other rocky planet . (Nobody knows for sure what size rocks lie at the cores of Jovian planets , or orbit other stars.) The Voyager 1 spacecraft took this picture in 1990 from the outer Solar System . This rock is so large its gravity makes it nearly spherical, and holds heavy gases near its surface. Yesterday, this rock started another orbit around its parent star , for roughly the 5 billionth time, spinning over 350 times during each trip. Happy Gregorian Calendar New Year to all the human inhabitants of this rock we call Earth .