Sigma: 2020-04-07

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The Solar System Beyond Pluto: The Hunt for Planet X

Scott S. Sheppard

April 7, 2020 at 7:30 P.M. at the Virginia Air and Space Center in downtown Hampton, Virginia


The Kuiper Belt, which has Pluto as the largest member, is a region of comet-like objects just beyond Neptune. This belt of objects has an outer edge, which we are only now able to explore beyond in detail with new modern cameras and large telescopes. Our team is performing the largest and deepest survey ever attempted to search for distant solar system objects. The ongoing search has discovered the most distant object ever orbserved in our Solar System and several of the largest known objects after the major planets. The survey has shown that the most extremely distant objects, which are beyond the Kuiper Belt and influence of the known major planets, are strangely grouped closely together in space. This suggests a yet unobserved planet more massive than the Earth is shepherding these extreme trans-Neptunian objects into similar orbits. I will discuss the most recent discoveries at the fringes of our solar system.


Scott S. Sheppard is an astronomer at the Carnegie Institution for Science in Washington, DC. He obtained his PhD from the University of Hawaii. Scott studies small bodies in our solar system in order to understand how the planets formed and migrated. If Guinness World Records had a record for the most moon discoveries, Sheppard would hold it as he has discovered over 100 moons around Jupiter, Saturn, Uranus and Neptune. Sheppard also discovered the first Neptune Trojan that trails behind Neptune in Neptune’s orbit as well as several dwarf planets that reside beyond Neptune. The asteroid 17898 Scottsheppard as well as three comets are named after him. Sheppard was lead discoverer of the most distant object ever observed in our solar system, 2018 VG18. In 2014, Sheppard along with colleague Chad Trujillo noticed all the extremely distant known small bodies have similar orbits. From this observation, they predicted a Super-Earth mass planet likely exists in our solar system some ten times further out than Pluto and it is shepherding these extremely distant smaller objects into their similar orbits.

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