Our parochial view of planets orbiting a central star — so familiar because it is the layout seen in the solar system — could be irrevocably shattered by new research that suggests giant, free-floating planets could form their own planetary systems. If true, that also means planetary systems may exist with no parent star.
These rogue planetary systems would also be much smaller than the solar system, possessing just a fraction of the total mass of our cosmic neighborhood.
The finding came about when a team of researchers used the James Webb Space Telescope (JWST) to examine young, isolated objects in space that are believed to have between five and 10 times the mass of Jupiter. These objects, unlike the planets of the solar system, were also unbound to a star and therefore free-floating in the universe.
These bodies could have formed in the same way stars form from collapsing clouds of gas and dust, hence their isolated nature. Yet, unlike stars, the free-floating planetary bodies would have failed to gather enough mass to trigger nuclear fusion in their cores, the process that defines what a main-sequence star is. That makes them akin to so-called “failed star” brown dwarfs, but with lower masses. Brown dwarfs have masses that range from 13 to 80 times the mass of Jupiter.
Alternatively, some free-floating planets are believed to have formed around stars from classic, swirling donuts of gas and dust called protoplanetary disks. They would’ve then been ejected from their home systems by gravitational interactions with their sibling planets and even with passing stars.
“These discoveries show that the building blocks for forming planets can be found even around objects that are barely larger than Jupiter and drifting alone in space,” Belinda Damian, lead author of the research and a scientist at the University of St. Andrews, said in a statement. “This means that the formation of planetary systems is not exclusive to stars but might also work around lonely starless worlds.”
The right stuff to spot planetary rogues
Believed to be the lowest mass bodies that can form from isolated clouds of gas and dust, free-floating planets are difficult to spot and study due to the fact that they emit very little light of their own. But the electromagnetic radiation free-floating planets do emit is mostly infrared light, the wavelength of light that the JWST is sensitive to.
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