Just 20 light-years from the Sun, a strange rogue planet without a star roams the Milky Way. And, according to a study published in The Astrophysical Journal, this strange, nomadic world has a magnetic field that is 4 million times stronger than Earth’s. Surprisingly, the exoplanet appears to be capable of producing spectacular auroras that would put our own northern lights to shame.
The new observations, made with the National Science Foundation’s Karl G. Jansky Very Large Array (VLA), are the first radio observations of a planetary-mass object outside our solar system, as well as the first time researchers have measured the magnetic field of such a body.
Sizing up SIMP
SIMP J01365663+0933473 (we’ll call it SIMP for simplicity’s sake) is a strange and untethered object that was first discovered in 2016. Simp was thought to be a brown dwarf at the time, an object that is too big to be a planet but too small to be a star. However, last year, another study showed that SIMP is just small enough, at 12.7 times the mass and 1.2 times the radius of Jupiter, to be considered a planet — albeit a mammoth one.
“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,” said Arizona State University’s Melodie Kao, who led the new study on SIMP, in a press release.
SIMP is also quite hot for a planet, with a surface temperature of over 1,500 degrees Fahrenheit (825 Celsius). The hottest planet in our solar system is Venus, with an average temperature of around 875 degrees Fahrenheit (470 degrees Celsius), while the Sun, a relatively small and cool star, has a surface temperature of around 10,000 degrees Fahrenheit (5,500 C). However, it’s important to note that Venus gets most of its heat from the Sun. And since solitary SIMP is not orbiting a star, its heat must be leftover from its initial formation some 200 million years ago. So, over time, the planetary goliath will continue to radiate away its warmth.
SIMP, according to the latest research, is not only gigantic by planetary standards, but it also has a magnetic field that is millions of times stronger than our own. Although the magnetic field aids SIMP in producing spectacular light shows, auroras are not generated in the same way they are on Earth.
Jupiter has, by far, the most powerful magnetic field in the solar system. Jupiter’s magnetic field is nearly 20,000 times stronger than Earth’s, resulting in stunningly bright auroras. Electrically charged particles are accelerated along Jupiter’s magnetic field lines before smashing into atoms in the planet’s upper atmosphere at speeds of around 3,000 miles (5,000 kilometers) per second.
The northern and southern lights are formed by a similar process on Earth; however, the charged particles that cause Earth’s auroras primarily come from the Sun in the form of solar wind. The charged particles on Jupiter, on the other hand, come primarily from its moon Io, rather than from the solar wind. Since SIMP does not have a star bombarding it with wind like Earth does, the researchers believe that SIMP’s auroras may be produced more like Jupiter’s, which means SIMP may have a moon.
To recap: SIMP seems to be a massive and magnetic exoplanet without a star that may have a moon that is generating brilliant auroras while wandering the Milky Way.
Whew. That’s impressive. But how will this fascinating find help astronomers learn more about the universe?
“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,” said Kao. “We think these mechanisms can work not only in brown dwarfs, but also in both gas giant and terrestrial planets.”
In other words, SIMP will help astronomers better understand how magnetic fields are generated in exoplanets. But wait, that’s not all!
“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,” said co-author Gregg Hallinan of Caltech.
So, there you have it. SIMP is a fascinating object in its own right, but more importantly, this new research opens the door to new insights into explanatory magnetic fields and auroras, as well as assisting in the search for exoplanets that seem to value their privacy.
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