Searching for Black Holes in the Outer Solar System with LSST

TL;DR

This paper explores the potential of LSST to detect or rule out black holes in the outer solar system, including Planet Nine, by observing accretion flares from impacts and constraining dark matter black holes.

Contribution

It demonstrates that LSST can rapidly test the black hole hypothesis for Planet Nine and other subsolar mass black holes in the Oort cloud, improving current dark matter constraints.

Findings

LSST can confirm or exclude Planet Nine as a black hole within a year.

LSST could significantly tighten limits on dark matter black holes in the outer solar system.

Impacts of Oort cloud objects produce detectable accretion flares for LSST observations.

Abstract

Planet Nine has been proposed to potentially be a black hole in the outer solar system. We investigate the accretion flares that would result from impacts of small Oort cloud objects, and find that the upcoming LSST observing program will be able to either rule out or confirm Planet Nine as a black hole within a year. We also find that LSST could rule out or confirm the existence of trapped planet-mass black holes out to the edge of the Oort cloud, indirectly probing the dark matter fraction in subsolar mass black holes and potentially improving upon current limits by orders of magnitude.