Planet 9 From Outer Space | 9am Tues, Apr 15, 2025

[Grigory Bronevetsky]

Modeling Talks

Planet 9 From Outer Space Konstantin Batygin, Caltech Tues, April 15, 2025 | 9am PT Meet | Youtube Stream Hi all, The presentation will be via Meet and all questions will be addressed there. If you cannot attend live, the event will be recorded and can be found afterward at https://sites.google.com/modelingtalks.org/entry/planet-9-from-outer-space More information on previous and future talks: https://sites.google.com/modelingtalks.org/entry/home Abstract: Over the past two decades, observational surveys have unveiled the complex 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, a distant portion of the trans-Neptunian objects exhibit behavior that defies explanation. Important details of the orbits of certain Kuiper belt objects and their detachment from Neptune's influence, along with the mysterious origins of highly inclined/retrograde long-period orbits pose significant challenges to conventional models of the Solar System. The peculiar dynamics of these distant solar system objects points to the presence of a yet-undetected planet, estimated to have a mass five times that of the Earth, with an orbital period of approximately ten thousand years. In this talk, I will review the observational evidence and dynamical arguments that underpin this hypothesis, and introduce exciting new evidence that further supports the case for Planet Nine. Bio: Professor Konstantin Batygin is a theoretical astrophysicist whose research focuses primarily on planetary astrophysics — in particular, the formation and evolution of solar systems throughout their lifespans. He also studies exoplanets and physical processes that occur in planetary interiors and atmospheres.  He received his bachelor’s in physics from UC Santa Cruz in 2008 before pursuing graduate studies at Caltech and joining the faculty in 2014. Batygin has been a visiting scientist at the Observatoire de la Cote D’Azure in Nice, France, and a prize postdoctoral fellow at Harvard University. In 2017, he was named a Packard Fellow in Science and Engineering. In his free time, he moonlights as a singer and guitarist for the rock band The Seventh Season.

[Grigory Bronevetsky]

Video: https://youtube.com/live/p0afD3U44sE

Slides:

- pdf: https://drive.google.com/file/d/1JI1riCvpomU65BKkXY4O97W0_qal5n3j/view?usp=sharing

- keynote: https://drive.google.com/file/d/1sfLCNpTUlbAfacRZ3vPzMAgf-qDfQp7o/view?usp=sharing

Summary:

• Solar system:

  • Planets

  • Asteroid belt

  • Kuyper belt: asteroids on the edge of the solar system beyond NEptune, shaped like a large donut

• Question: why does the Kuyper belt exist

• History:

  • The gas giant started in smaller orbits and there was debris beyond their orbits

  • As the debris was tossed around by the planets, the orbits of the gas giants became more eccentric

  • Then, dynamical friction stabilized them

• Observation:

  • Many objects in Kuyper belt have eccentric elliptical orbits that are tilted in a consistent way relative to the solar system’s orbital plant

  • To reproduce the data we need a body of 5 Earth Masses on a 20k year obit

  • Must have a specific inclination relative to the solar system’s plane to pull the bodies out in this pattern

  • Only objects along the plane of this body stay in stable orbits; others get ejected by Neptune

  • There is a population of bodies with variable angles relative to the orbital plane

• Simulations show that given the normal 8 planets there should be few objects with closest approach to the sun within the orbit of Neptune (the gas giants should toss them out)

  • However, it turns out that we do see many such objects

  • Such a population could be sustained by a new body

  • Data (still sparse) shows many objects with closest approach within Neptune orbit

  • Caveat: objects that come closer to the sun are easier to discover but this bias can be controlled for

• LSST: https://www.lsst.org/

  • Survey of long-period Kuyper belt objects

  • In a few years we should know of ~40k such objects

  • We hope that this dataset will be sufficient to settle this question either via direct detection or by statistics

  • Chellenge:

    • We know Planet 9’s orbit and mass

    • We don’t know where it is on its path right now

    • LSST is in the southern hemisphere, may not be pointing in the right direction

    • We also don’t know how reflective it is