Ever since Pluto was demoted from planet to dwarf planet in 2006, astronomers have been wondering whether Neptune really is the most distant planet from the sun. Now, a new telescope could uncover what lies in the farthest reaches of the solar system. The Vera C Rubin Observatory released its first images this week, and soon the world’s most powerful digital camera will be pointing across the whole of the night sky. Scientists are hopeful that if planet nine exists, the telescope will find it within its first year of operation. Ian Sample is joined by Dr Scott Sheppard, an astronomer at the Carnegie Institution for Science, to find out how Pluto lost its planetary status, why scientists think there could be another super-Earth, and why planet nine has been so hard to find