After more reading on this intriguing report I pass along these observations.
Astronomers uncover largest group of rogue planets yet,
https://phys.org/news/2021-12-eso-telescopes-uncover-largest-group.html
Reference paper, A rich population of free-floating planets in the Upper Scorpius young stellar association,
https://www.nature.com/articles/s41550-021-01513-x, 22-Dec-2021.
My observation. From the abstract cited, "Therefore, ejections due to dynamical instabilities in giant exoplanet systems must be frequent within the first 10 Myr of a system’s life." My note. All these possible rogue planets reported are dated very young in the area near the Sun studied (relative to the age of the Sun, some 4.6 billion years old), perhaps 10 million years old or less. One possible formation mechanism identified is ejection from other planetary systems that formed (obviously very recently too relative to the solar system age). This seems to require much catastrophism and violence during protoplanetary disk evolution events postulated to explain the origin of planets. Another question, what is the MMSN protoplanetary disk mass and size needed for large scale, planetary ejections to create a population of rogue planets in the MW? Recent studies on interstellar objects (much smaller than rogue planets) said to pass through our solar system, were ejected from massive disks. Our Sun MMSN is only about 3,330 earth masses or so in many models. My note, from the phys.org report, "We did not know how many to expect and are excited to have found so many,". This indicates that a specific origin model using gas clouds and protoplanetary disks, did not predict how many rogue planets could be found, so the exact formation of rogue planets is not certain, like heliocentric solar system astronomy. Example, measurements for the solar parallax based upon Mercury and Venus transits, used to define the distance between Earth and the Sun or observations of the phases of Venus. My note. The phys.org report states, The study suggests there could be many more rogue planets that have not been discovered. "There could be several billions of these free-floating giant planets roaming freely in the Milky Way without a host star," Bouy explains." My note. This suggest that billions of rogue planets may exist, free floating in the MW. Do observations like this impose constraints on the postulated evolutionary events in the solar, protoplanetary disk that Earth is said to evolve from? Example, what constrained our Earth from evolving, *naturally* into a wandering, rogue Earth in the MW?