ABSTRACT

Over the past two decades, observational surveys have progressively unveiled the complex orbital structure of the Kuiper Belt, revealing a myriad of icy bodies orbiting the Sun beyond Neptune. While many orbital behaviors within this region adhere to predictions based on the known eight-planet Solar System, a distant portion of the trans-Neptunian object (TNO) census exhibits dynamics that defy explanation. Notably, the physical clustering of orbits with semi-major axes exceeding ~250 AU, the detachment of perihelia of certain Kuiper belt objects from Neptune's influence, and the mysterious origins of highly inclined/retrograde long-period orbits pose significant challenges to the conventional Solar System model. The peculiar dynamical architecture of these distant solar system objects suggests the presence of a yet-undetected planet, estimated to have a mass M9 ~ 5M⊕, orbiting on moderately inclined orbit with a semi-major axis a9 ~ 400−800 AU and eccentricity e9 ~ 0.2−0.6. In this talk, I will review the observational evidence and dynamical arguments that underpin this hypothesis, and introduce a new line of evidence that further substantiates the case for Planet Nine.

About the Speaker:

Professor Konstantin Batygin received his bachelor's degree in Astrophysics from University of California, Santa Cruz in 2008, before pursuing graduate studies in Planetary Science at Caltech and receiving a Ph.D. in 2012. Batygin's research is primarily aimed at understanding the formation and evolution of planetary systems, including our own. Prior to joining the faculty at California Institute of Technology in 2014, Batygin was a postdoctoral scholar at Observatoire de la Cote d'Azur in Nice, France, and Harvard University. When not science-ing, he plays in the rock band The Seventh Season.