A mysterious large object is floating around outside our solar system and researchers aren’t sure exactly what it is – although it could be a rogue planet.
In the first radio-telescope detection of a planetary-mass object beyond our solar system, astronomers have found the strange celestial body has 12.7 times the mass of Jupiter. It doesn’t appear to orbit a parent star, however, and is only 20 light-years away from Earth.
“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,” study lead astronomer Melodie Kao said.
A brown dwarf is an object too large to be a planet, but isn’t big enough to sustain the nuclear fusion of hydrogen in its core that is vital to stars.
The object, which has been named SIMP J01365663+0933473, was first detected in 2016, but was thought to be a brown dwarf. The latest data reveals it’s younger than first thought at a relatively youthful 200 million years old, and its mass is smaller, so it could be classified as a planet. Its temperature is also far cooler than the sun, at 825 degrees Celsius. It also has a strong magnetic field, 200 times the strength of Jupiter.
The researchers were able to pick up on the object’s magnetic activity using a powerful radio astronomy observatory called the Very Large Array, a National Science Foundation facility in New Mexico.
The methods used suggest the researchers may have “a new way of detecting exoplanets, including the elusive rogue ones not orbiting a parent star,” researcher Gregg Hallinan said.
Subsequent observations showed that some brown dwarfs have strong auroras, similar to those seen in our own Solar System’s giant planets. The auroras seen on Earth are caused by our planet’s magnetic field interacting with the solar wind. However, solitary brown dwarfs do not have a solar wind from a nearby star to interact with. How the auroras are caused in brown dwarfs is unclear, but the scientists think one possibility is an orbiting planet or moon interacting with the brown dwarf’s magnetic field, such as what happens between Jupiter and its moon Io.
The strange object in the latest study, called SIMP J01365663+0933473, has a magnetic field more than 200 times stronger than Jupiter’s. The object was originally detected in 2016 as one of five brown dwarfs the scientists studied with the VLA to gain new knowledge about magnetic fields and the mechanisms by which some of the coolest such objects can produce strong radio emission. Brown dwarf masses are notoriously difficult to measure, and at the time, the object was thought to be an old and much more massive brown dwarf.
The difference between a gas giant planet and a brown dwarf remains hotly debated among astronomers, but one rule of thumb that astronomers use is the mass below which deuterium fusion ceases, known as the “deuterium-burning limit”, around 13 Jupiter masses.
Simultaneously, the Caltech team that originally detected its radio emission in 2016 had observed it again in a new study at even higher radio frequencies and confirmed that its magnetic field was even stronger than first measured.
“When it was announced that SIMP J01365663+0933473 had a mass near the deuterium-burning limit, I had just finished analyzing its newest VLA data,” said Kao.
The VLA observations provided both the first radio detection and the first measurement of the magnetic field of a possible planetary mass object beyond our Solar System.
Such a strong magnetic field “presents huge challenges to our understanding of the dynamo mechanism that produces the magnetic fields in brown dwarfs and exoplanets and helps drive the auroras we see,” said Gregg Hallinan, of Caltech.
“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. We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets,” Kao said.
“Detecting SIMP J01365663+0933473 with the VLA through its auroral radio emission also means that we may have a new way of detecting exoplanets, including the elusive rogue ones not orbiting a parent star,” Hallinan said.
James E Windsor, Overpasses News Desk
August 3rd, 2018