A strange rogue planet not far from Earth has provided researchers with a new mystery through its incredibly — and inexplicably — powerful magnetic field.
Initially thought to be a brown dwarf star, SIMP J01365663+0933473 is part of a cluster of brown dwarfs called the Carina-Near stellar moving group, about 20 light-years away. Brown dwarfs are a difficult to classify celestial body: at 13 to 80 times the mass of Jupiter, they’re too big to be called planets, but at the same time they’re not massive enough to initiate the nuclear fusion process necessary to become a star. However, SIMP’s mass was recently discovered to only be 12.7 more massive than Jupiter, so it has been proposed that it be considered a planet; as it doesn’t orbit a star, this would make it a rogue planet, drifting through the cosmos without a parent sun.
But SIMP J01365663+0933473’s rogue status is just part of a list of oddities displayed by this gas giant: It rotates quickly, with one day lasting only 2.4 Earth hours; changes in the light being emitted from the planet over the course of SIMP’s short days suggest that it has evolving weather patterns in its clouds; and it has a massive magnetic field, more than 200 times stronger than Jupiter’s magnetosphere; this results in auroras around SIMP strong enough for radio astronomers to pick up on their radio emissions.
To put SIMP J01365663+0933473’s magnetic field into perspective, Jupiter’s magnetosphere can be up to 64 times more powerful than Earth’s magnetic field, meaning that SIMP’s field is nearly thirteen thousand times stronger than Earth’s. This could lead to a new way of detecting exoplanets, through the radio emissions generated from their aurorae.
"This particular object is exciting because studying its magnetic dynamo mechanisms can give us new insights on how the same type of mechanisms can operate in extrasolar planets — planets beyond our solar system," explains lead study author Melodie Kao, an astrophysicist with Arizona State University. Researchers do not know what the source of such a strong magnetosphere would be, or the source of the auroras for that matter, but they are taking advantage of these unique properties to expand their understanding of how the magnetic fields of both planets and stars work.
"This object is right at the boundary between a planet and a brown dwarf, or ‘failed star,’ and is giving us some surprises that can potentially help us understand magnetic processes on both stars and planets," Kao continues. "We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets."