2025-07-15 国立天文台
2023 KQ14（赤線）と他の3つのセドノイドの軌道（白線）。この天体は軌道上で太陽に近い、太陽から71天文単位の位置で発見されました。黄色い点は2025年7月時点の位置を表します。（クレジット：国立天文台）
＜関連情報＞
- https://www.nao.ac.jp/news/science/2025/20250715-subaru.html
- https://subarutelescope.org/jp/results/2025/07/14/3573.html
- https://www.nature.com/articles/s41550-025-02595-7
近日点距離66 auのセドナ型天体の発見とダイナミクス Discovery and dynamics of a Sedna-like object with a perihelion of 66 au
Ying-Tung Chen,Patryk Sofia Lykawka,Yukun Huang,JJ Kavelaars,Wesley C. Fraser,Michele T. Bannister,Shiang-Yu Wang,Chan-Kao Chang,Matthew J. Lehner,Fumi Yoshida,Brett Gladman,Mike Alexandersen,Edward Ashton,Young-Jun Choi,A. Paula Granados Contreras,Takashi Ito,Youngmin JeongAhn,Jianghui Ji,Myung-Jin Kim,Samantha M. Lawler,Jian Li,Zhong-Yi Lin,Hong-Kyu Moon,Surhud More,… Ji-Lin Zhou
Nature Astronomy Published:14 July 2025
DOI:https://doi.org/10.1038/s41550-025-02595-7
Abstract
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.
