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Space

'Fossil' Discovered Beyond Pluto Implies 'Something Dramatic' Happened 400M Years Ago (space.com) 20

"The distant reaches of the Solar System are still mysterious," writes ScienceAlert. "Not much sunlight pierces these regions, and there are strong hints that undiscovered objects lurk there. The objects that astronomers have discovered in these dim reaches are primordial, and their orbits suggest the presence of more undiscovered objects."

And now thanks to the giant 8.2-meter Subaru telescope at Hawaii's Mauna Kea Observatory, astronomers have discovered "a massive new solar system body located beyond the orbit of Pluto," reports Space.com. The weird elongated orbit of the object suggests that if "Planet Nine" exists, it is much further from the sun than thought, or it has been ejected from our planetary system altogether.

The strange orbit of the object, designated 2023 KQ14 and nicknamed "Ammonite," classifies it as a "sednoid." Sednoids are bodies beyond the orbit of the ice giant Neptune, known as trans-Neptunian objects (TNOs), characterized by a highly eccentric (non-circular) orbit and a distant closest approach to the sun or "perihelion." The closest distance that 2023 KQ14 ever comes to our star is equivalent to 71 times the distance between Earth and the sun... This is just the fourth known sednoid, and its orbit is currently different from that of its siblings, though it seems to have been stable for 4.5 billion years.

However, the team behind the discovery, made using Subaru Telescope as part of the Formation of the Outer Solar System: An Icy Legacy (FOSSIL) survey, thinks that all four sednoids were on similar orbits around 4.2 billion years ago. That implies something dramatic happened out at the edge of the solar system around 400 million years after its birth. Not only does the fact that 2023 KQ14 now follows a unique orbit suggest that the outer solar system is more complex and varied than previously thought, but it also places limits on a hypothetical "Planet Nine" theorized to lurk at the edge of the solar system.

There's "no viable transfer mechanisms" to explain the observed orbits "with the current configuration of planets," according to the team's recently-published paper. But since those orbits are stable, it "suggests that an external gravitational influence beyond those of the currently known Solar System planets is required to form their orbits." So where does that leave us? ScienceAlert summarizes the rest of the paper — and where things stand now: Astronomers have proposed many sources for this external gravitational influence, including interactions with a rogue planet or star, ancient stellar interactions from when the Sun was still in its natal cluster, and the capture of objects from other lower-mass stars in the Solar System's early times. But the explanation that gets the most attention is interactions with a hypothetical planet, Planet Nine.

If Planet Nine exists, it has a huge area to hide in. Some astronomers who have studied its potential existence think it could be the fifth largest planet in the Solar System. It would be so far away that it would be extremely dim. However, we may be on the cusp of detecting it, if it exists. The Vera Rubin Observatory recently saw first light and will begin its decade-long Legacy Survey of Space and Time (LSST). The LSST will find transient events and objects in the Solar System like no other telescope before it. It's purpose-built to find hard-to-detect objects, and not even an elusive object like Planet Nine may be able to hide from it.

'Fossil' Discovered Beyond Pluto Implies 'Something Dramatic' Happened 400M Years Ago

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