En (ny) nionde stor planet upptäckt

"the work does not explain the "Kuiper cliff," the lack of objects with orbit semimajor axes between 50 and 70 AU. It would be very nice (from an aesthetic standpoint, anyway) if the same planet could also be blamed for those apparently missing worlds. But it can't, at least not yet:

Another curious feature of the distant scattered disk is the lack of objects with perihelion distance in the range q = 50–70 AU. It is yet unclear if this property of the observational sample can be accounted for by invoking a distant eccentric perturber such as the one discussed herein. Indeed, answering these questions comprises an important avenue toward further characterization of our model.

http://www.planetary.org/blogs/emily...-planet-9.html


Based on estimations of the primordial mass required to form Uranus and Neptune, as well as bodies as large as Pluto (see below), earlier models of the Kuiper belt had suggested that the number of large objects would increase by a factor of two beyond 50 AU,[61] so this sudden drastic falloff, known as the "Kuiper cliff", was completely unexpected, and its cause, to date, is unknown. In 2003, Bernstein and Trilling et al. found evidence that the rapid decline in objects of 100 km or more in radius beyond 50 AU is real, and not due to observational bias. Possible explanations include that material at that distance was too scarce or too scattered to accrete into large objects, or that subsequent processes removed or destroyed those that did.[62] Patryk Lykawka of Kobe University has claimed that the gravitational attraction of an unseen large planetary object, perhaps the size of Earth or Mars, might be responsible

https://en.wikipedia.org/wiki/Kuiper_belt