The discovery of planetary systems beyond our solar system has posed
challenges to established theories of planetary formation. Planetary orbits
display a variety of architectures not predicted by first principles, and
free-floating planets appear ubiquitous. The recent discovery of candidate
Jupiter Mass Binary Objects (JuMBOs) by the James Webb Space Telescope (JWST)
further expanded this enigma. Here, by means of high-accuracy, direct N-body
simulations, we evaluate the possibility that JuMBOs may form as a result of
ejection after a close stellar flyby. We consider a system of two Jupiter-like
planets moving in circular orbits with velocities v1β and v2β at distances
a1β and a2β around a Sun-like star. The interloper is another Sun-like star
approaching with asymptotic velocity vββ. We find that JuMBOs can indeed
be formed upon ejection if the two planets are nearly aligned as the interloper
reaches the closest approach. The ratio of the cross section of JuMBOs
production to that of single ejected free-floating planets can approach βΌ20% for vββ/v2ββΌ0.1β0.2 and a1β/a2ββΌ0.75β0.8. JuMBOs
formed via this channel are expected to have an average semi-major axis
comparable to Ξa=(a2ββa1β) and high eccentricity, with a distinctive
superthermal distribution which can help to observationally identify this
formation channel and distinguish it from primordial formation. If the ejection
channel is confirmed for these or future JWST observations, these JuMBOs will
directly inform us of the conditions where these giant planets formed in
protoplanetary disks, putting stringent constraints on the giant planet
formation theory.Comment: 18 pages, 5 figures. Videos are available at
https://yihanwangastro.github.io/#posts