Can planet–planet binaries survive in star-forming regions?

ABSTRACT Significant numbers of free-floating planetary-mass objects have been discovered in nearby star-forming regions by the JWST, including a substantial number (42) of Jupiter Mass Binary Objects (‘JuMBOs’) in the Orion Nebula Cluster (ONC). The JuMBOs have much wider separations than other populations of substellar binaries, and their existence challenges conventional theories of substellar and planetary-mass object formation. Whilst several theories have been proposed to explain their formation, there has yet to be a study that determines whether they could survive the dynamical encounters prevalent within a dense star-forming region. We place a population of planet–planet binaries in N-body simulations of dense star-forming regions and calculate their binary fraction over time. We find that between 50 and 90 per cent of planet–planet binaries are destroyed on time-scales of a few Myr, which implies that many more must form if we are to observe them in their current numbers. Furthermore, if the ONC was much more dense at formation, the initial separation distribution of the JuMBOs must have been even wider (and less similar to other substellar binaries) than the observed distribution.