Orion has scientists puzzling anew over what constitutes a planet. Three of the areas within the Orion constellation where the free-floating objects, unhitched to any star, have been discovered. The free-floating objects have masses from five to 15 times that of Jupiter. Generally, objects 13 times the mass of Jupiter or less are classified as planets. But unlike a planet, the orphans are unattached to any central star, such as Earth's sun.
Astronomers say the find is raising fundamental questions about the origins of planet-size objects.
Other astronomers have found about 50 planets outside the solar system, but those planets were in the orbit of a central star. Like stars, they are thought to form when interstellar gas clouds contract and fragment to become the seeds for star birth. Less-powerful nuclear reactions can heat larger brown dwarfs, but below a certain mass, even those fires don't ignite and the dwarfs are heated only because gravity compresses them. To some astronomers, such an absence of nuclear reactions represents a defining point between planet and brown dwarf, according to Adam Burrows, an astrophysicist at the University of Arizona in Tucson. Instead, he says, origins should define the two types of objects.