An object within a 200-million-year-old group of stars known as Carina-Near thought to be a brown dwarf when it was discovered is actually a rogue planet, according to a group of researchers who published their findings in The Astrophysical Journal Letters.
Brown dwarfs make up the lowest level of stellar classification. They are larger and more massive than giant planets and fuse deuterium, an isotope of hydrogen, in their cores, for a limited time.
While they cannot sustain the fusion, they remain hot and bright for a long time before gradually cooling and contracting. Their temperatures, therefore, are a function of their ages. Young brown dwarfs can be as hot as stars while old ones are as cool as planets, explained study co-author Jackie Faherty of the American Museum of Natural History (AMNH).
SIMP J013656.5+093347, also known as SIMP0136, was discovered in a location where brown dwarfs are often found, a cluster of stars all approximately the same age moving together.
Knowing their ages and temperatures are the same or close to those of the other stars in the cluster enables scientists to determine brown dwarfs’ masses.
Led by Jonathan Gagne of Carnegie Science, researchers from AMNH, the Institute for Research on Exoplanets (iREX) at Universite de Montreal, and the University of California at San Diego, determined the object has a mass 13 times that of Jupiter, putting it at the boundary between brown dwarfs and planets.
This surprised other scientists who had already been studying SIMP0136 and found it to have rapidly changing weather patterns on its surface.
“The implication that the well-known SIMP0136 is actually more planet-like than we previously thought will help us to better understand the atmospheres of giant planets and how they evolve,” Gagne said.
While rogue or free floating planets such as SIMP0136 are similar to other gas giant exoplanets, they are easier to study because the light they emit is not obscured by that of host stars.