Exoplanets are planets located outside our solar system. Currently, more than 5,000 exoplanets have been discovered. These planets are expected to orbit stars in a manner similar to the planets in our solar system. However, some exoplanets seem to be “free-floating” in space, not orbiting any particular star. The mystery of their formation deepened in the fall of 2023 when astrophysicists, using the James Webb Space Telescope, identified massive floating binary objects about the size of Jupiter, which they named JuMBOs (Jupiter-mass binary objects).
These newly reported objects have puzzled astrophysicists. However, astrophysicist Rosalba Perna from Stony Brook University, along with colleagues Yihan Wang and Zhaohuan Zhu from UNLV, proposed a new theory. In a paper published in Nature Astronomy, they demonstrated through N-body simulations – a common tool for describing the dynamics of cosmic particles – that JuMBOs can be formed as a result of ejection following a close flyby with another star.
“These exoplanets cannot be easily explained by standard theories of planetary formation,” says Perna, a Professor in the Department of Physics and Astronomy. “Our recent work highlights stellar interactions as an important factor in the development of unusual planetary systems in dense stellar environments, and it suggests free-floating binary planets may be formed in such regions.”
Essentially, she explains, the idea based on our theory is that two planets are originally in outer orbits of a planetary system.
“Our simulations demonstrate that close encounters can lead to a ‘kick’,” adds Yihan Wang, “resulting in the ejection of a pair of giant planets, a fraction of which remains bound and gives rise to JuMBOs”.
The research leading to this theory and the paper are supported in part by the National Science Foundation, NASA, and the Nevada Center for Astrophysics.