Some scientists are surprised to find evidence for many more loose planetary bodies, not connected with a stellar system, than they had assumed existed. The rest of this post is excerpts:
...a new study, published in today's [May 20, 2011] issue of Nature,[and reviewed by Sky and Telescope] suggests that a complete census of "big bodies" drifting loose in our galaxy might actually total nearly one trillion — because Jupiter-mass "planets" in interstellar space might well outnumber the stars themselves....
Theorists are chuckling, "We told you so!" They've argued for years that the galaxy should teem with unbound planets. Some have proposed that objects with masses almost as low as Jupiter's form the way normal stars do, directly from collapsing clouds of gas and dust. Think of these as undersized brown dwarfs. Others point out that the chaos that seems to prevail in many just-formed solar systems must cause many close encounters among planets that yield "winners" (those that remain in orbit) and "losers" (those that get flung out of the system entirely).
...statistics imply that most of the loose planet-mass objects aren't just low-mass stellar wannabes — there are too many of them. Instead, the researchers believe they're finding bodies that have been ejected from unstable planetary families — and, by extension, that planetary systems should be the norm, not the exception, for the Milky Way's hundreds of billions of stars.
This also implies that early chaos in planetary systems is common. Exoplanet researchers had already concluded that this is the case from the large number of explanets that have been left in highly eccentric orbits, which they could not have formed with.
...a new study, published in today's [May 20, 2011] issue of Nature,[and reviewed by Sky and Telescope] suggests that a complete census of "big bodies" drifting loose in our galaxy might actually total nearly one trillion — because Jupiter-mass "planets" in interstellar space might well outnumber the stars themselves....
Theorists are chuckling, "We told you so!" They've argued for years that the galaxy should teem with unbound planets. Some have proposed that objects with masses almost as low as Jupiter's form the way normal stars do, directly from collapsing clouds of gas and dust. Think of these as undersized brown dwarfs. Others point out that the chaos that seems to prevail in many just-formed solar systems must cause many close encounters among planets that yield "winners" (those that remain in orbit) and "losers" (those that get flung out of the system entirely).
...statistics imply that most of the loose planet-mass objects aren't just low-mass stellar wannabes — there are too many of them. Instead, the researchers believe they're finding bodies that have been ejected from unstable planetary families — and, by extension, that planetary systems should be the norm, not the exception, for the Milky Way's hundreds of billions of stars.
This also implies that early chaos in planetary systems is common. Exoplanet researchers had already concluded that this is the case from the large number of explanets that have been left in highly eccentric orbits, which they could not have formed with.
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