A mystery ‘small world’ has been discovered in our solar system, according to scientists.

‘Ammonite’ is the nickname given to the new 380-kilometer world discovered by the Subaru Telescope at the Mauna Kea Observatory in Hawaii.

It is regarded as a “fossil” with preserved “memories of the solar system’s infancy” and becomes the fourth member of the sednoids, a collection of small bodies with odd orbits around the solar system’s edge, according to the scientists.

The history of senoids began in 2003 when NASA scientists discovered Sedna, a dwarf planet located around eight billion miles from Earth and at the time the most distant object in the solar system.

According to a 2021 research, Sedna was most likely formed in the solar system “at the early stage of its evolution,” and dynamic processes that followed the sun’s creation within a crowded star cluster caused its orbit to alter.

Other explanations include the possibility that Sedna originated from a low-mass star or that the orbit was altered by a stellar encounter, such as Scholz’s star passing roughly 70,000 years ago at a distance of 52,000 astronomical units from the Sun.

In any case, Ammonite’s presence gives space scientists some answers to their questions—and more.

“In recent years, spacecrafts have been sent to various small bodies in the Solar System for close observation and sample collection. However, these spacecrafts have only explored limited regions of the Solar System,” Dr Fumi Yoshida, of the University of Occupational and Environmental Health and the Chiba Institute of Technology and leader of the Formation of the Outer Solar System: An Icy Legacy (FOSSIL) project, said in a statement.

“Most of the vast Solar System remains unexplored. Wide-field observations with the Subaru Telescope are steadily pushing back the frontier,” the doc added.

In March, May, and August of 2023, the telescope detected a possible object in the solar system’s outskirts. More recent observations made with the telescope in July of last year confirmed the object, which is thought to have a diameter of between 220 and 380 kilometers, as well as its orbit.

Astronomers searching through the archives discovered that the object had been observed at the Kitt Peak National Observatory in 2005, more than 20 years ago, and in 2021 and 2014.

“These findings have enabled the compilation of 19 years of observational data, significantly improving the accuracy of Ammonite’s orbit,” the researchers added.

It’s intriguing that Ammonite now ‘follows an orbit different from the other sednoids’, indicating that ‘the outer solar system is more diverse and complicated than previously imagined’. This, in particular, calls into question the possibility of the fictitious planet in the farthest regions of the solar system.

The strange orbital clustering of several far-off, ice objects was eventually explained by the theory.

Dr Yukun Huang at the Center for Computational Astrophysics (CfCA) of NAOJ, who conducted simulations of Ammonite’s orbit, said: “The fact that Ammonite’s current orbit does not align with those of the other three sednoids lowers the likelihood of the Planet Nine hypothesis. It is possible that a planet once existed in the Solar System but was later ejected, causing the unusual orbits we see today.”

Dr Yoshida added: “Ammonite 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 Ammonite formed.”

“Understanding the orbital evolution and physical properties of these unique, distant objects is crucial for comprehending the full history of the Solar System.”

“At present, the Subaru Telescope is among the few telescopes on Earth capable of making such discoveries. I would be happy if the FOSSIL team could make many more discoveries like this one and help draw a complete picture of the history of the Solar System.”