Astronomers Discover ‘Ammonite’: A New Sednoid in Our Solar System

Astronomers using the Subaru Telescope in Hawaii have identified a new celestial object, designated 2023 KQ14 and nicknamed 'Ammonite,' which orbits the sun beyond Pluto. This discovery, announced in a paper published on July 15, 2025, in the journal Nature Astronomy, not only expands our understanding of the solar system but also raises questions regarding the existence of a theoretical Planet Nine.

Ammonite is classified as a sednoid, a term denoting objects located beyond Neptune with highly eccentric orbits, akin to the known dwarf planet Sedna. Sednoids are particularly intriguing to astronomers as they provide insights into the dynamics of the outer solar system. According to Dr. Yukun Huang, a researcher at the National Astronomical Observatory of Japan, Ammonite's orbit does not align with those of the existing sednoids, which might challenge the prevailing theories surrounding Planet Nine.

Historically, the search for a ninth planet has gained momentum due to the peculiar clustering of certain minor bodies in the Kuiper Belt. A study conducted in June 2025 by researchers from Rice University and the Planetary Science Institute estimated a 40% probability for the existence of such a planet. These findings stem from the gravitational effects that appear to 'herd' various objects into their current orbits.

Ammonite follows a unique trajectory, coming as close as 66 astronomical units (AU) from the sun and reaching distances of up to 252 AU. This contrasts with Sedna's orbit, which ranges from about 76 AU to a staggering 900 AU. The significance of Ammonite's discovery lies not just in its classification but also in the implications it holds for understanding the gravitational influences at play in the far reaches of our solar system. As Dr. Huang noted, “The fact that 2023 KQ14’s current orbit does not align with those of the other three sednoids lowers the likelihood of the Planet Nine hypothesis.”

The object was discovered as part of the FOSSIL (Formation of the Outer Solar System: An Icy Legacy) survey project, which aims to study the icy bodies in the outer solar system. The name 'Ammonite' draws inspiration from the ammonite fossils, which are remnants of ancient cephalopods that perished approximately 66 million years ago. The discovery process involved multiple observations, with findings confirmed in July 2024 using the Canada-France-Hawaii Telescope, and even archival images dating back 19 years provided critical data for computing Ammonite's orbit.

In summary, the discovery of Ammonite (2023 KQ14) not only adds to the catalog of known celestial bodies but also fuels ongoing discussions about the structure and composition of our solar system. As researchers continue to analyze the implications of this new sednoid, the mystery of Planet Nine remains tantalizingly unresolved, with Ammonite's unique characteristics possibly reshaping our understanding of distant planetary dynamics. Future observations will be crucial in determining the full impact of this discovery on our knowledge of the solar system and its many secrets.