Ancient “ammonite” objects found in deep freezing of the solar system

Astronomers have discovered a distant trans-North River object (TNO), which has a rare orbit that may help solve the lingering mystery about the formation of the solar system. Nicknamed “Ammonite”, the object was appointed 2023 kq14 with a fence distance of 66 astronomical units (AU) and a half-hair axis of 252 AU, placing it in an elusive SEDNA-like object.

The findings are reported in journals Natural Astronomy Researchers surveyed by Fossil II use the Subaru telescope.

Why ammonia is important

Only three other known objects have similar distant places, and these orbits are largely not affected by Neptune’s gravity. These SEDNA-like bodies provide rare clues to the early structures of the solar system, and there may be an undiscovered giant planet that goes far beyond Neptune.

Ammonite is unique because it fills the previously empty orbital space area called the “encircled spiral gap” that spans 50 to 75 au. Its stable orbit has been confirmed by 4.5 billion years of simulations that it has been largely undisturbed since the infancy of the solar system.

Key points of discovery

• Ammonite is the fourth known SEDNA-like object and the third largest distance from the enclosure ratio (66 au).
• According to numerical simulations, its orbit is dynamically stable within 4.5 billion years.
• This object helps bridge gaps in known orbits, thus perfecting the model of early solar system evolution.
• Its orbit does not match the clustering of previously observed sedna-like objects.

What makes this track unusual?

Unlike SEDNA and others, the fence longitude of the amino group is almost opposite, indicating that it may belong to a separate orbital population. This challenges existing models that show that all such objects are affected by the same external forces, such as the now-shrouded rogue planet or the hypothetical “Nine Planets.”

Interestingly, when ammonia ore was included in simulations of early orbit clustering, the researchers observed loose alignments about 4.2 billion years ago, suggesting the possibility of a common primitive origin. However, this alignment is weaker than previous objects, raising new questions about Sedna-like orbital diversity.

Researched quotes

“Our analysis suggests that amino groups and other SEDNA-like objects may have shared original orbital clustering around 4.2 GA,” the authors wrote. They noted that Ammonite’s orbital “filled with previously unexplained ‘Q-GAPs in distant TNO distributions.”

Meaning and next steps

The discovery of ammonia has given scientists a rare observation in a remote and informed space area. By amplifying known high-rise Tnos populations, it reinforces efforts to test the hypothesis of original orbit clustering and the potential existence of potential giant planets.

In-depth investigations in the future, including ongoing observations from the Subaru telescope and new tools such as the Vera C. Rubin Observatory, may discover more of these objects. Each new discovery helps refine the architecture of the solar system and may be exposed to long-term planetary effects lurking outside known planets.

doi: 10.1038/S41550-025-02214-3

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