Free Astronomy Magazine March-April 2016

PLANETOLOGY ducted with the Japanese Subaru Telescope, located on Mauna Kea, Hawaii. With its single 8.2 meters diam- eter mirror, the capacity of observing in the near-infra- red and a field of view 75 times larger than that pro- vided by the neighbouring Keck telescopes, Subaru is considered the best instru- ment for confirming (or re- butting) the existence of Planet Nine. Involved with the observing campaign are also Trujillo and Sheppard, both strong supporters of Batygin and Brown’s the- ory. Obviously there are no certainties at the moment: the orbital clustering of the KBOs examined could just be an extraordinary coinci- dence and perhaps soon will be found objects of that kind with orbital charac- teristics incompatible with the existence of Planet Nine. What does not instead re- present a problem is the position of Planet Nine in such remote location, since it is in fact indisputable, as confirmed by the ob- servation of numerous extrasolar systems, that planets isolated in the outer outskirts are recurrent (just as recurrent are planets of 10-15 Earth masses, apparently absent in our solar system). Since they cannot have formed where we see them, it is likely that they arrived so far from their stars as a result of gravitational interactions with other significant size planets. Moreover, already in 2012, David Nesvorný (Southwest Research Institute, Department of Space Studies, Boulder, Col- orado) had shown through computer sim- ulations that most likely more than 4 bil- lion years ago there were 5 large sized planets in our system solar. What has be- come of the fifth one? Was it permanently ejected or just transferred itself to an outer orbit? 170 years ago celestial mechanics allowed to discover Neptune. Since then there has never been such strong evidence of the existence of a large unknown planet at the edge of our solar system. n O n the side, the Subaru telescope. With its 8.2 meters di- ameter monolith- ic mirror, breadth of the field of view (unmatched among large tele- scopes) and sen- sitivity to the infrared, it is the instrument most suited in the world to search for Planet Nine.