Planet Formation Before Solar Formation
Location: Outside U.S.
Date: April 2011
Is it possible that some planets could have formed before the sun ignited?
Yes, it is possible, but unlikely. The planets in our solar system
began to accrete from dust left over from the Sun's ignition, after
the Sun ignited.
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighboring region of planetesimals.
So no. The definition we have assigned to the word "planet" requires a star to orbit around.
See the following URL for amplification:
The general consensus is that stars form prior to their attendant
planets. So while prior planets could form (as far as I know that does not
violate any physical laws) to my knowledge such reverse formation has not
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Update: June 2012