Alternatives The IAU's working definition is not always used. One alternate suggestion is that planets should be distinguished from brown dwarfs on the basis of their formation. It is widely thought that giant planets form through core accretion, which may sometimes produce planets with masses above the deuterium fusion threshold; massive planets of that sort may have already been observed. Brown dwarfs form like stars from the direct gravitational collapse of clouds of gas, and this formation mechanism also produces objects that are below the limit and can be as low as . Objects in this mass range that orbit their stars with wide separations of hundreds or thousands of Astronomical Units (AU) and have large star/object mass ratios likely formed as brown dwarfs; their atmospheres would likely have a composition more similar to their host star than accretion-formed planets, which would contain increased abundances of heavier elements. Most directly imaged planets as of April 2014 are massive and have wide orbits so probably represent the low-mass end of a brown dwarf formation. One study suggests that objects above formed through gravitational instability and should not be thought of as planets.
alternatives the iau's working definition is not always used one alternate suggestion is that planets should be distinguished from brown dwarfs on the basis of their formation it is widely thought that giant planets form through core accretion which may sometimes produce planets with masses above the deuterium fusion threshold; massive planets of that sort may have already been observed brown dwarfs form like stars from the direct gravitational collapse of clouds of gas and this formation mechanism also produces objects that are below the limit and can be as low as  objects in this mass range that orbit their stars with wide separations of hundreds or thousands of astronomical units (au) and have large star/object mass ratios likely formed as brown dwarfs; their atmospheres would likely have a composition more similar to their host star than accretion-formed planets which would contain increased abundances of heavier elements most directly imaged planets as of april 2014 are massive and have wide orbits so probably represent the low-mass end of a brown dwarf formation one study suggests that objects above formed through gravitational instability and should not be thought of as planets