found in the Orion Nebula. And the latter have divided some astrophysicists into two camps -- planet believers and planet debunkers.
The new work by the Carnegie Institution's Alan Boss lands firmly on the side of planet debunkers by recognizing the role that magnetic fields could play in relaxing the gravitational gas collapses that are thought to yield stars and then solar systems.
The low-mass, free floating objects form like stars, so they are not planets, Boss said. Instead, they should be called sub-brown dwarfs -- objects that are smaller than typical
-- which are failed stars too small to shine and burn their fuel.
"This model suggests that free floating planetary mass objects in Orion could have formed in [the] same process as stars and just continued down to lower masses," Boss said in an interview. "So they should be considered part of the star-formation process rather than as being planets which have been ejected from a protoplanetary disk."
If widely agreed on, the model could strike an intellectual blow to certain scientists, including Patrick Roche of the University of Oxford and Philip Lucas of the University of Hertfordshire, who have
such low-mass bodies and labeled them planets. Findings like theirs tend to attract extra attention from reporters and the public excited about the prospects for worlds, and life, beyond our planet and solar system.
Too bad for the search for life
Boss's explanation for the free-floaters builds on his previous work and introduces the new magnetic fields variable.
"Magnetic fields are a part of the puzzle that theorists like to leave out because they complicate matters, but observers know they are there," Boss said. "This is a first attempt to include them in a crude approximation."
Previous models of star formation suggest that the process could only yield stars and other bodies with masses no less than 13 times the mass of Jupiter.
In conventional models, planets (smaller, colder and incapable of burning fuel or shining) form later around stars when a massive leftover dust disk spins around a central star and cools, with small bodies eventually coalescing, colliding and gaining mass to become planets.
In Boss' model, as the dust and gas of a protostellar disk collapses, magnetic fields help stop the cloud from fusing into a single object at the center of the cloud. The cloud remains distended and then breaks up into smaller mass objects. On top of that, the magnetic tension helps the cloud rebound from its center as it cools, again assisting the formation of smaller objects, Boss said.
Four or more prestellar objects, each with a mass as low as Saturn, may form in this way, he said. Eventually such an unstable system could eject single fragments that would continue to gather a bit of mass to reach those reported among the "Orion free-floaters."
"These little objects, if they form in a multiple system, won't become stars," Boss said. "They are tossed out at such an early phase that they lack the gas to become big stars. They are stellar embryos. They end up with a mass you'd associate with planetary mass even though they form like stars."
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