This article was originally published on The Conversation. Read the original article. Ever since enthusiasm started growing over the possibility that there could be a ninth major planet orbiting the sun beyond Neptune, astronomers have been busy hunting it. One group is investigating four new moving objects found by members of the public to see if they are potential new solar system discoveries. As exciting as this is, researchers are also making discoveries that question the entire prospect of a ninth planet.
One such finding is our discovery of a minor planet in the outer solar system: 2013 SY99. This small, icy world has an orbit so distant that it takes 20,000 years for one long, looping passage. We found SY99 with the Canada-France-Hawaii Telescope as part of the Outer Solar System Origins Survey. SY99’s great distance means it travels very slowly across the sky. Our measurements of its motion show that its orbit is a very stretched ellipse, with the closest approach to the sun at 50 times that between the Earth and the sun (a distance of 50 “astronomical units”). READ MORE