A planetary model fails too
More new research also points away from categorizing the Orion free-floaters as planets. Geoff Bryden at NASA's Jet Propulsion Laboratory has modeled a scenario that shows solar systems are unlikely to kick out objects with masses similar to those of the free-floaters.
Instead, they might eject smaller objects, Bryden said.
"For this reason, our models do not account very well for observations of young, free floating, 10-Jupiter-mass objects," he said. "There are alternatives, such as the effect of other stars passing nearby, but probably the most promising way to form such objects is along the lines of Boss' paper."
Mark McCaughrean of the Astrophysical Institute in Potsdam, Germany, called Boss's approach "perfectly reasonable."
But he questioned the observational data -- from Lucas and Roche and others -- against which Boss is testing his new model, saying the free-floaters could be quite a bit more massive than those researchers claim.
"We still have a lot of work ahead of us to prove whether or not such objects [with masses below that of 13 Jupiters] really exist in star-forming regions," he said. "In any case, this knocks another wooden stake through the hearts of the P-word (planet) users: if fragmentation really can produce objects [with the same mass as Jupiter] floating freely like this, then there's even less justification for using the confusing P-word: 'sub-brown dwarfs' will do very nicely."
A new working definition
Birthright aside, can a planet-sized object that fails to orbit a star still be called a planet? The standards-setting International Astronomical Union (IAU) recently issued a provisional answer -- no way. Planets, by their new definition, must orbit a star. That definition could be revised as more data come in and the group continues to meet.
The new definition, released in February, is the result of a sometimes contentious months-long process that
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