JWST Just Found Something Scary Drifting Through Space That Shouldn't Exist

Microlensing surveys have spent thirty years finding planets that have no star. The MOA nine-year survey put terrestrial-mass free-floating planets at roughly twenty for every star in the Milky Way, which makes the dark, unlit world the default planet in this galaxy and the sunlit kind the exception. This is the full story: Einstein's 1936 throwaway paper, the 2011 result that was too big and got corrected, the 41.5-minute event that is the shortest ever recorded, Webb's unexplained pairs in Orion, and the ice giant our own solar system probably threw away. Primary sources referenced: Einstein, A. (1936), Science 84, 506 - lens-like action of a star Paczynski, B. (1986), ApJ 304, 1 - gravitational microlensing by the galactic halo Sumi, T. et al. (2011), Nature 473, 349 - unbound or distant planetary-mass population Mroz, P. et al. (2017), Nature 548, 183 - no large population of unbound Jupiter-mass planets Mroz, P. et al. (2020), ApJL 903, L11 - OGLE-2016-BLG-1928, terrestrial-mass candidate Sumi, T. et al. (2023), AJ 166, 108 - free-floating planet mass function, MOA-II nine-year survey Pearson, S. & McCaughrean, M. (2023) - JWST planetary-mass objects in the Trapezium Cluster Stevenson, D. (1999), Nature 400, 32 - life-sustaining planets in interstellar space Abbot, D. & Switzer, E. (2011), ApJL 735, L27 - the Steppenwolf planet Nesvorny, D. (2011), ApJL 742, L22 - young solar system's fifth giant planet Luhman, K. (2014), ApJL 786, L18 - WISE J0855-0714 Kao, M. et al. (2018), ApJS - radio aurorae on SIMP J01365663+0933473 Johnson, S. et al. (2020), AJ 160, 123 - predicted Roman free-floating planet yield