There are no physical boundaries in space. The solar system consists of eight planets orbiting around one star: the Sun. Neptune, the farthest planet from the Sun, orbits approximately 30astronomical units from the Sun. An astronomical unit is a unit of length used by astronomers. One astronomical unit equals the distance from Earth to the Sun: 93 million miles (149 million km). Some of the comets associated with the solar system travel on orbits that take them much farther from the Sun than Neptune.
HubbleSite and STScI are not responsible for content found outside of hubblesite.org and stsci.edu