The Oort cloud is a vast, spherical region of space thought to surround the Sun, with a radius
measured in thousands of astronomical units (1 AU being the Earth-Sun distance). Evidence for it
comes from the orbits of long-period comets, which seem to hail from a great distance from the Solar
System. This schematic shows how the Solar System is an insignificant part of the Sun's family.
Solar System and Oort Cloud