![]() And, because heavier molecules form under cooler conditions, the spectra also reflect the object's temperature. To confirm that the new objects truly had cool, planet-like temperatures, the team used measurements from spectrographs on the Keck telescopes in Hawaii to study the range, or spectrum, of energy emitted by three of their candidates.īecause different types of molecules emit characteristic spectra, these measurements can tell researchers about an object's chemical makeup. Planets never become massive enough, and thus not hot enough, to host the nuclear reactions that take place inside stars and brown dwarfs.īut, a brown dwarf also can emit light that looks red from Earth if it's veiled by a dusty cloud. Their results turned up 18 different objects, whose relatively dim, reddish light suggests the cool temperatures of planets. ![]() ![]() They studied surveys of this region performed by visible and infrared light-detecting "cameras" on telescopes in mainland Spain, the Canary Islands, and Hawaii. The researchers selected the sigma Orionis star cluster for their planet hunt because it's nearby, young, and largely free of dust and gas clouds that might obstruct the view. The team also is the first to collect spectrographic information about the planets' temperature and composition. In this case, however, the Science authors detected light emitted directly from the 18 objects. Typically, researchers infer the planets' presence by measuring the wobbling of their central stars caused by the planets' gravitational pull. Reports of planets outside our solar system have been rolling in at an accelerating pace recently-the current tally is well over 50-but Zapatero Osorio's group is among the first to identify its candidates directly. "The formation of young, free-floating, planetary-mass objects like these are difficult to explain by our current models of how planets form," said lead author Maria Rosa Zapatero Osorio, of the Instituto de Astrofísica de Canarias, in Tenerife, Spain, and currently working at the California Institute of Technology, in Pasadena, California. They lack a central star like our sun, and they are part of a star cluster, sigma Orionis, that is no more than five million years old. The objects discovered by the Science researchers seem to have quite a different origin and evolutionary history. Planets are generally thought to form over tens of millions of years, as gas and dust in the disk swirling around a star condenses and clumps together.
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