Free Astronomy Magazine March-April 2016

PLANETOLOGY however not lim- ited to only pro- vide a possible ex- planation of the orbital behaviour of the analyzed KBOs sample, as they also created some objects ar- ranged on orbits almost perpen- dicular to that of Neptune. In effect, of those objects there are in reality at least 5, and their un- usual orbits (in- explicable so far) and individual po- sitions on the orbit are perfectly in agree- ment with the simulations, such that they acquire consistency. But one thing is find- ing what it is looked for in a targeted way, and quite another is that also the com- putational by-products replicate real sce- narios in which all protagonists are already known. To date, no alternative hypothesis to the presence of a planet with the character- istics identified by Batygin and Brown can explain the orbital properties of the 6 most distant KBOs of the solar system. Confi- dent in its existence, the two researchers decided to informally call it Planet Nine and began to explore the possibility to ob- serve it directly; and thus effectively dis- cover it and not only virtually. The main obstacle is the very vague know- ledge of its orbit, so much so that Planet Nine could follow a large number of sig- nificantly different orbits, all equally valid for the purpose of the performed simula- tions. Moreover, there is the need to under- stand, at least in broad outlines, at which point of the orbit it is. If it were near the perihelion, then perhaps it would have al- ready been discovered. According to Brown it is instead more like- ly that it lies in intermediate positions or even at the aphelion, a region expected to project itself in a portion of sky that in- cludes the crowed plane of the Milky Way T he Palomar Observatory image that made possible the dis- covery of Sedna (centre of the cir- cle), the KBO that along with 2012 VP 113 renewed the hypothesis of the existence of a new trans-Neptu- nian planet. The brightest star just above Sedna is as bright as Pluto. I n this diagram are represented, by bundles of black lines, the possible positions, dis- tances, magnitudes and apparent speed of Planet Nine. The red lines demarcate the Milky Way, while the blue line is the ecliptic. It is easy to guess that the search for that hy- pothetical object will take a rather long time. [Konstantin Batygin & Mike Brown]