"They're probably brother and sister," Gagliuffi said, referring to the two object's similarity in size and age.
A brown dwarf is a star too small to burn its hydrogen in the way that our Sun burns. It is believed, however, that a brown dwarf can fuse deuterium, a heavy isotope of hydrogen, causing it to emit a very weak light. But young planets also produce heat from within as they cool.
While it could be assumed that the pair are stellar in nature, exact measurement is difficult with current astronomical tools.
There are many known binary stars, but only one known binary planet system; Pluto and its "moon" Charon. Astrobiologists are interested in dual planet systems because it is believed they have a higher chance of sustaining life.
If Gagliuffi's pair are planets, it is assumed that they must orbit a star, but that star (or absence thereof) has not been confirmed. The intriguing binary system is observed through what Gagliuffi calls "a whole zoo of different stars," making it hard to get accurate data.