Free Astronomy Magazine March-April 2016

of observations in the search for any feed- back, but since only 20% of the entire sky has been recorded in this mode, it will thus also be necessary to rely on luck. Meanwhile, Batygin is constantly refining the parameters of the simulations, in order to restrict as much as possible the area of sky within which to search for the planet. For his part, Brown has arranged a five- year observational campaign to be con- MARCH-APRIL 2016 PLANETOLOGY T his diagram compares the orbits of the outer planets with those of the more distant KBOs and that of the hypothetical Planet Nine. On this latter it is shown the path along which, according to Brown and Batygin, we will be more likely to see the planet. [JPL; Batygin and Brown/Caltech; A. Cuadra/Science] and that has not yet been covered by more deeper photographic surveys. If it were near the aphelion, Planet Nine would then be moving very slowly and would have a magni- tude around 22 (if not weaker) and would have therefore been off-limits to all large past surveys. A punctiform image of the planet might nevertheless already exist and be hidden in the WISE (Wide-field Infrared Survey Ex- plorer) database, within a limited number of observations conducted at the most ex- treme infrared wavelengths accessible by this instrument. The above-mentioned Luh- man is at present looking into that series B elow left, the dome of the Subaru telescope, and more to the right the ones of the Keck twin telescopes. On the Subaru are pinned the hopes of finding Plan- et Nine. [NAOJ]