On January 20, 2016, a release from California Institute of Technology (Caltech) stunned people around the world. It stated that, based on mathematical modeling and computer simulations, a massive ninth planet may exist in the outer Kuiper Belt. If such a world is orbiting out there, it must be very distant. The implications of its existence are profound, affecting our understanding of the Kuiper Belt and how this distant world may have formed in the infant Solar System and been "kicked out" to its present position.
The Discovery of Planet 9's Possible ExistenceDr. Konstantin Batygin and Dr. Michael Brown of Caltech worked together to decipher the odd orbital characteristics of strangely grouped objects in the outer Solar System, some observed by Gemini Observatory's Dr. Chad Trujillo. The Caltech scientists concluded that there must be an object herding these objects (Note 1). According to their simulations, it has to be much more massive than Earth and orbit in the outer reaches of the Kuiper Belt.
Previous studies have suggested that massive objects exist in the outer parts of the Solar System such as the one predicted by Dr. Patryk Sofia Lykawka and Dr. Tadashi Mukai of Kobe University in their 2008 paper (Note 2). They also provided the orbital information. Brown and Batygin's latest work implies that a truly planet-mass object exists. These studies are based on one of the most long-standing disciplines in the astronomy: celestial mechanics.
How Astronomers Will Find Planet 9Batygin and Brown have a rough orbital calculation for the object. Now, they and other astronomers must use modern instruments to look for this world, and confirm its existence.
That is why Dr. Brown keeps coming back to Hawaii – to look for objects beyond Neptune's orbit, in the outermost reaches of the Solar System. His next observation will use the Subaru Telescope in March. It is a time exchange program between the Subaru Telescope and the W. M. Keck Observatory. What is the camera of his choice at Subaru? Yes – it will be the Hyper Suprime-Cam (HSC) with sensitive CCDs, offering a very wide field of view equivalent of nine full moon areas. This makes it extremely suitable for finding a faint object if you are not sure of where it is, but have rough idea where it can be.
Dr. Chad Trujillo based at Gemini Observatory, is an expert on objects in the outer Solar System and says, "I'd be surprised if all of the telescopes on Maunakea aren't involved in studies of the 9-th Planet." He adds that large telescopes with wide-field capabilities will be needed to find the planet in the first place since it is probably very faint. "Once discovered, virtually every telescope on Maunakea, and around our planet, will be involved in characterizing the planet to learn properties such as its mass and composition," says Trujillo.
Dr. Jun-ichi Watanabe of the National Astronomical Observatory of Japan, the expert on the Solar System who also was a member of the Planet Definition Committee at the International Astronomical Union's General Assembly in 2006 (where "dwarf planet" category was established), is not only intrigued by this result but also excitedly awaits confirmation from the observations. The discovery may come from the existing telescopes such as the Subaru Telescope or other survey telescopes, some under construction. Which one of them is the most promising? It should be obvious. That is why he and his research team also keeps coming back to use the Subaru Telescope.
Konstantin Batygin and Mike Brown, "Evidence for a Distant Giant Planet in the Solar System", Astronomical Journal, 151, pp. 22-33, in February 2016.
Patryk S. Lykawka and Tadashi Mukai, "An Outer Planet beyond Pluto and the Origin of the Trans-Neptunian Belt Architecture", Astronomical Journal, 135, pp. 1161-1200, in April 2008.