Discovery and dynamics of a Sedna-like object with a perihelion of 66 au

Ying-Tung Chen^1*, Patryk Sofia Lykawka², Yukun Huang³, JJ Kavelaars^4,5,6, Wesley C. Fraser^1,4,5, Michele T. Bannister⁷, Shiang-Yu Wang¹, Chan-Kao Chang¹, Matthew J. Lehner^1,8, Fumi Yoshida^9,10, Brett Gladman⁶, Mike Alexandersen¹¹, Edward Ashton¹, Young-Jun Choi¹², A. Paula Granados Contreras¹, Takashi Ito^3,10, Youngmin JeongAhn¹², Jianghui Ji¹³, Myung-Jin Kim¹², Samantha M. Lawler¹⁴, Jian Li^15,16, Zhong-Yi Lin¹⁷, Hong-Kyu Moon¹², Surhud More^18,19, Marco Muñoz-Gutiérrez²⁰, Keiji Ohtsuki²¹, Lowell Peltier⁵, Rosemary E. Pike¹¹, Tsuyoshi Terai²², Seitaro Urakawa²³, Hui Zhang²⁴, Haibin Zhao¹³, Ji-Lin Zhou¹⁶

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

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

Trans-Neptunian objects (TNOs) with large perihelion distances (q > 60 au) and semi-major axes (a > 200 au) provide insights into the early evolution of the Solar System and the existence of a hypothetical distant planet. These objects are challenging to observe, and thus their detections are still rare, yet they play a crucial role in constraining models of Solar System formation. Here we report the discovery of a Sedna-like TNO, 2023 KQ₁₄, nicknamed ‘Ammonite’, with q = 66 au, a = 252 au and inclination i = 11°. The orbit of Ammonite does not align with those of the other Sedna-like objects and fills the previously unexplained ‘q-gap’ in the observed distribution of distant Solar System objects. Simulations demonstrate that Ammonite is dynamically stable over 4.5 Gyr. Our analysis suggests that Ammonite and the other Sedna-like objects may have shared a primordial orbital clustering around 4.2 Ga. Furthermore, the stable orbit of Ammonite favours larger orbits (~500 au) rather than closer ones for a large hypothetical planet in present-day trans-Neptunian space.

Keywords: Sedna-like object, Trans-Neptunian object (TNO), Kuiper belt, Solar System dynamics, Early Solar System formation