Remarkably, there appears to be no live contract on either Kalshi or Polymarket on the existence of Planet Nine.

Had those venues existed in 2016, there certainly would have been plenty of liquidity and a tight spread. When the reporter called, I tried to come on like a scientist, “I believe that the probability that Planet Nine exists is 68.3%.”

It might still be out there, biding its time. I asked an agent to propagate the 21,740 synthetic Brown-Batygin Planet Nine orbits that survive survey cuts to November 1, 2026. At each point on a 0.5° sky grid, the agent counted the fraction of the corpus lying within a 10° angular radius, then plotted that fraction in color on the Mollweide projection of the sky. The darkest point contains 13.5% of the surviving orbits within 10°:

As expected, the sweetest spot continues to lie in the region where the ecliptic intersects the galactic plane. As Galileo remarked in 1610, “Upon whatever part of it the telescope is directed, vast crowds of stars is immediately presented to view.” Luhman 16AB provides inspiration. It’s a remarkable low-mass binary brown dwarf just 6.5 light years away, yet its position near the plane allowed it to elude detection for years.

It caught my eye last week when I read that a bright KBO, 2026 ED138 was extracted from the LSST survey in a region near the galactic plane on the fringe of the Planet Nine search space. Moreover, a preprint by Han et al. note that it’s recoverable in the TESS data.

The key trick is to subtract the expected PSFs of all the Gaia stars in each frame. When one does that (or more precisely when one’s agent does that) the S/N is massive.

Here’s the trajectory for Orcus, which lies in an uncrowded region away from the galactic plane. Dealing with stars behind the track is not particularly daunting:

Compare that to what one is up against near the plane:

The technique of subtracting the Gaia PSFs makes recovery of the known KBOs look like fish in a barrel:

S/N of 40 at magnitude 20.46 is impressive. The list keeps going but one gets the point.

Currently the fan of the M4 is highly audible. And agents don’t sleep…