Evidence of controversial Planet 9 uncovered in sky surveys taken 23 years apart

Paper and claimed detection

• Commenters link the arXiv paper and note its amusing leftover title (“Overleaf Example”), but otherwise treat it as a serious attempt to cross‑match IRAS (1983) and AKARI (2006) infrared data.
• One reader who examined the figures says the object is obvious in IRAS but not visibly apparent in the AKARI image; they’re told the second detection is in the catalog data, not visually obvious in that plot.

Is this the Planet 9?

• A strong critique cites that if the two detections are the same object, its inferred orbit must have high inclination, which is incompatible with the low‑inclination body required by the Batygin & Brown Planet 9 hypothesis that explains Kuiper Belt object clustering.
• Consensus in that subthread: even if real, this object is “super interesting” as a massive trans‑Neptunian or Oort‑cloud‑like body, but likely not the canonical Planet 9.

Pluto, “dwarf planets,” and what counts

• Large subthread revisits Pluto’s demotion: some insist Pluto “will always be the 9th planet” and argue the current definition (orbit‑clearing, etc.) is arbitrary and pedagogically motivated.
• Others reply that similar reclassification already happened with Ceres and the asteroids; calling Pluto a Kuiper Belt object is analogous and avoids having to treat hundreds of TNOs as planets.
• Various alternative classification schemes are proposed: grandfather Pluto only; add Eris, Ceres, and several others as full planets; or accept that “all definitions are wrong, some are useful.”

Primordial black hole Planet 9

• Many are fascinated by the idea that Planet 9 might be a primordial black hole (PBH) with Earth‑scale mass and centimeter‑scale radius.
• Enthusiasts emphasize its scientific value: nearby lab for quantum gravity, tests of black‑hole physics, and extreme Oberth maneuvers.
• Others push back: at the distances involved, even a normal cold planet is nearly invisible; a PBH isn’t needed to explain non‑detection, and its Hawking radiation would be undetectably faint at planetary masses.
• Safety concerns are discussed; multiple comments stress that a black hole’s gravitational effects at a distance are no worse than any object of the same mass.

Distance, scale, and capture

• There’s extensive debate on how best to convey “700 AU”: 15× Pluto’s distance, ~0.01 light‑years, ~4 light‑days, ~4× Voyager 1’s distance are all proposed.
• Some are amazed the Sun can bind an object so far away; others point out it’s still ~400× closer than the nearest star.
• Capture mechanics provoke a mini‑lesson in orbital dynamics: two‑body capture is impossible without energy loss or third‑body interactions, contrary to some initial intuitions.

Utility and missions

• Several speculate on missions: with travel times scaled from New Horizons, a probe might reach such a planet within a human lifetime if future propulsion improves.
• A few dream about using a PBH for power or time‑dilation experiments, but others note the immense technical gap and that fusion is a far nearer‑term goal.