You might be thinking about a giant trilobite found on Pluto, or maybe a dinosaur skeleton on the planet. However, when astronomers use the word “fossil” for 2023 KQ14, they are not referring to a bone in rock, but an orbit that appears to have survived largely unchanged since the Solar System was young.

Found by the Subaru Telescope’s FOSSIL survey and nicknamed Ammonite, this world loops around the Sun on a path so distant and detached that Neptune can’t easily tug it, making it a pristine record of ancient dynamics.

What is this “outer space fossil” like?

Its key stats read like a dare: perihelion ≈66 astronomical units, semimajor axis ≈252 AU, period ≈4,000 years, and an inclination of about 11°. It’s only the fourth member of the ultra-rare sednoid clan.

Sednoids matter because they shouldn’t be easy to make. Anything that swings much closer than ~40 AU gets sculpted by Neptune. Push perihelion past 60 AU, though, and you enter a dynamical quiet zone where objects keep their original marching orders. That’s why researchers call Ammonite a fossil: model runs suggest its orbit has drifted by over billions of years. In a Solar System famous for shuffling the deck, this card stayed put.

What is Planet Nine?

For years, a handful of distant objects seemed to “aim” their closest-approach directions the same way, a curious lineup that some teams argued could be shepherded by a hidden giant planet far beyond Neptune. Ammonite complicates that neat picture because its perihelion points the other way.

Far from killing the idea, the new fossil forces a rewrite: any real Planet Nine would have to sit farther out or elsewhere than earlier fits allowed—or the clustering was a mirage born of small-number statistics and discovery bias. Either way, this fossil tightens the screws on theory.

How do we know Ammonite is real and not a fleeting blip? First, the discovery team dug up precovery images (older pictures where the object was hiding in plain sight)stretching its observation arc across many years.

Second, the Minor Planet Center issued an MPEC with a robust orbit solution. And then, Subaru and NAOJ released analyses showing that when you integrate its motion forward and backward for the age of the Solar System, the fossil barely budges. That long-term calm means Ammonite is an unusually clean test particle for probing the deep past.

On the Planet Nine question, smart money now splits in two. One camp says the fossil calls for a different planet—colder, dimmer, and in a new orbital orientation—to keep the rest of the sednoids stable without disturbing Ammonite.

The other camp argues the clustering was never compelling; add one fossil that points the opposite way and the pattern dissolves..

How it was discovered?

You might wonder how a team finds a dot this faint so far away. The Subaru Telescope combines a huge mirror with a wide camera to sweep the outer Solar System, then software hunts for slow movers night after night. When the FOSSIL survey flagged 2023 KQ14, astronomers pulled archival images to extend its track, improving the orbit enough to predict where the fossil would be months later. With each added position, the uncertainty shrank, and the object’s odd, high-perihelion path came into focus.

Numbers to pocket: at discovery, Ammonite was near 71 AU from the Sun; its brightness suggests a diameter of a few hundred kilometers (exact size depends on reflectivity). The object takes ~4 millennia to loop the Sun once and won’t approach the planets closely. That’s perfect for a fossil—quiet, slow, stubbornly informative.

What’s next? The Vera C. Rubin Observatory will soon pour out a decade of deep, wide images, likely turning four sednoids into dozens. If more align with the older group, Planet Nine gets a second wind; if many look like Ammonite, the clustering case fades and early-epoch explanations gain ground. Either outcome is a win, because each new fossil adds a line to the Solar System’s origin story.