Scientists have found a small and icy object, designated 2023 KQ14 and nicknamed "Ammonite". It is far beyond Neptune and is currently orbiting the Sun. Ammonite, a name based on fossilised sea creatures, has been classified as a sednoid, not a planet or dwarf planet. Scientists have previously explained that a sednoid is a trans-Neptunian object (TNO) with a large semi-major axis, a distant perihelion and a highly eccentric orbit. This TNO is the fourth sednoid ever found.
The object was discovered using the Subaru Telescope in Hawaii as part of the FOSSIL (Formation of the Outer Solar System: An Icy Legacy) survey project. It was first spotted in March, May and August 2023 and confirmed in July 2024.
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As per a paper published in Nature Astronomy on July 14, the object is estimated to be 300-700 km in diameter and likely composed of ice, rock and organic compounds.
When it comes to orbital characteristics, the object has a perihelion of 66 astronomical units (AU). One AU is the average distance between the Earth and the Sun. Meanwhile, aphelion is 252 AU. The object has followed a stable orbit for at least 4.5 billion years.
"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," the authors explained in their paper.
"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," Dr Yukun Huang of the National Astronomical Observatory of Japan (NAOJ), who is also a co-author of the paper, said in a press release.
"It is possible that a planet once existed in the Solar System but was later ejected, causing the unusual orbits we see today."
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According to study co-author Dr Fumi Yoshida, Neptune is the only known massive object near the outer Solar System that could have shaped the orbits of the TNOs and Sednoids. However, Ammonite is quite far away.
"2023 KQ14 was found in a region far away where Neptune's gravity has little influence. The presence of objects with elongated orbits and large perihelion distances in this area implies that something extraordinary occurred during the ancient era when 2023 KQ14 formed," Yoshida said.
The object is considered a "fossil" from the early solar system as it supposedly preserves conditions from 4.5 billion years ago. Scientists aim to use Ammonite's discovery to fill a longstanding gap in the basic understanding of distant orbits.
