By Ron Cowen
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Recent reports have sparked a vigorous debate about just what constitutes a planet.
The controversy escalated last summer when astronomers began unveiling images of star-forming regions showing a multitude of low-mass objects. Based on estimates of their mass alone, the bodies would seem to qualify as planets (SN: 10/7/00, p. 228). Yet, they roam freely and dont orbit a parent star.
Last month, British astronomers led by Philip W. Lucas of the University of Hertfordshire in Hatfield and Patrick F. Roche of the University of Oxford announced that infrared spectra of the roughly 20 roaming bodies they found in the Orion nebula contain signs of water vapor. This indicated that these objects are extremely lightweight, a hallmark of planethood. The team reports its findings in an upcoming Monthly Notices of the Royal Astronomical Society.