Discovery and Dynamics of a New Sedna-like Object with a Perihelion of 66 au

Ying-Tung Chen^1*, Patryk Sofia Lykawka², Yukun Huang³, JJ Kavelaars^4,5, Wesley C. Fraser^4,1, Michele T. Bannister⁶, Shiang-Yu Wang¹, Chan-Kao Chang¹, Matthew J. Lehner^1,7, Fumi Yoshida^8,9, Brett Gladman¹⁰, Mike Alexandersen¹¹, Edward Ashton¹, Young-Jun Choi¹², A. Paula Granados Contreras¹, Takashi Ito^9,13, Youngmin JeongAh¹², Jianghui Ji¹⁴, Myung-Jin Kim¹², Samantha M. Lawler¹⁵, Jian Li^16,17, Zhong-Yi Lin¹⁸, Hong-Kyu Moo¹², Surhud More^19,20, Marco Muñoz-Gutiérrez²¹, Keiji Ohtsuki²², Lowell Peltier⁵, Rosemary E. Pike¹¹, Tsuyoshi Terai²³, Seitaro Urakawa²⁴, Hui Zhang²⁵, Haibin Zhao^14,26, Ji-Lin Zhou¹⁶

¹Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Taiwan
²Kindai University, Higashiosaka, Osaka, Japan
³National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan
⁴Herzberg Astronomy and Astrophysics Research Centre, National Research Council of Canada, Victoria, BC, Canada
⁵Department of Physics and Astronomy, University of Victoria, Victoria, BC, Canada
⁶School of Physical and Chemical Sciences, University of Canterbury, Christchurch, New Zealand
⁷Department of Physics and Astronomy, University of Pennsylvania, ph, USA
⁸University of Occupational and Environmental Health, Kitakyusyu, Japan
⁹Planetary Exploration Research Center, Chiba Institute of Technology, Narashino, Chiba, Japan
¹⁰Department of Physics and Astronomy, University of British Columbia, Vancouver, BC, Canada
¹¹Center for Astrophysics / Harvard & Smithsonian, Cambridge, MA, USA
¹²Korea Astronomy and Space Science Institute, Daejeon, Korea
¹³Center for Computational Astrophysics, National Astronomical Observatory of Japan, Mitaka, Tokyo, Japan
¹⁴CAS Key Laboratory of Planetary Sciences, Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing, China
¹⁵Campion College and the Department of Physics, University of Regina, Regina, SK, Canada
¹⁶School of Astronomy and Space Science, Nanjing University, Nanjing, China
¹⁷Key Laboratory of Modern Astronomy and Astrophysics in Ministry of Education, Nanjing University, Nanjing, China
¹⁸Institute of Astronomy, National Central University, Zhongli, Taoyuan, Taiwan
¹⁹Inter-University Centre for Astronomy and Astrophysics, Pune, India
²⁰Kavli Institute for the Physics and Mathematics of the Universe (WPI), Kashiwa, Chiba, Japan
²¹Instituto de Astronomía y Ciencias Planetarias, Universidad de Atacama, Copiapó, Chile
²²Department of Planetology, Kobe University, Kobe, Japan
²³Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI, USA
²⁴Japan Spaceguard Association, Bisei Spaceguard Center, Ibara, Okayama, Japan
²⁵Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai, China
²⁶CAS Center for Excellence in Comparative Planetology, Hefei, China

* Presenter:Ying-Tung Chen, email:ytchen@asiaa.sinica.edu.tw

Trans-Neptunian objects with large perihelion distances (q > 60 au) and semi-major axes (a > 200 au) provide important constraints on early solar system evolution and the existence of hypothetical distant planets. We report the discovery of a new Sedna-like trans-Neptunian object, ``Ammonite", with q = 66 au, a = 251 au, and i = 10.98°. Dynamical simulations show Ammonite's orbit is highly stable over 4.5 Gyr, with less than 1% variation in its semi-major axis. Simulations also suggest a primordial clustering of orbits around 4.2 Gyr ago for Ammonite and the other three largest-q objects. Ammonite's stability is sensitive to the semi-major axis of a hypothetical planet, being unstable with a_Planet ~ 380 au but much less perturbed with a_Planet ~ 500 au. These findings offer insight into the dynamical behaviors of distant solar system objects and provide constraints on the orbits of a hypothetical planet.

Keywords: Solar System, Trans-Neptunian objects, Detached objects, Planetary dynamic, Orbit determination