The brightest, most intense aurora ever observed was recorded above a brown dwarf found 18 light years away from Earth.
As the captivating play of hues was being recorded by the telescopes, scientists were chalking down more arguments to the nature of brown dwarfs, a puzzling question for decades. Ar they indeed failed stars as most would label them, or should we see brown dwarfs more akin to planets?
With the red, yellow and green hues shining one million times more intense above the brown dwarf than the northern lights above Earth, scientists drew closer to drawing a conclusion. Brown dwarfs, the massive yet poorly lit and cold outer-solar system celestial bodies are closer to planets than to stars.
According to Professor of Astronomy at the California Institute of Technology and author of the study, Gregg Hallinan:
“What defines a star is if it’s big enough to fuse hydrogen at its core. Brown dwarfs don’t quite have enough mass to burn hydrogen throughout their lifetime; they’re liked failed stars. So the question you might ask: is a brown dwarf more like a planet or more like a star?”
A possible answer might stem from studying the magnetic fields of the brown dwarf under question, titled LSRF 1835+3259. These have different manifestations if they surround a star or if they surround a planet.
Within our own solar system, all planets that also have magnetic fields, exhibit bright aurorae above the surface. These are typically associated with radio pulses transmitted at the same time as the aurora is taking place.
Three telescopes were thus pointed in the direction of LSRF 1835+3259, lying in the Lyra constellation. They would record the radio pulses of the brown dwarf and pick up all optical data they could.
The telescopes are the Very Large Array Telescope of the National Radio Astronomy Observatory, as well as the W.M. Keck Observatory Telescope and the Palomar Hale Telescope. With their aid, the researchers observed that every 2.48 hours, as the brown dwarf was completing one rotation, it would emit radio pulses. At the same time, an aurora, 10,000 times more intense than any observed on Jupiter would light the celestial body’s surface.
This was the first time that aurorae were recorded outside of the solar system.
Gregg Hallinan gave us an idea of how bright these aurorae are:
“In the case of the brown dwarf, the aurora is so much more powerful than anything we’ve seen in our Solar System. Jupiter’s aurorae are 1,000 times more powerful than the Earth’s aurorae. Well, this brown dwarf has aurorae that are at least 10,000 times more powerful than Jupiter’s aurora.”
Brown dwarfs are typically between 75 and 80 times the mass of Jupiter. This particular brown dwarf also comprises 80 Jupiter masses, albeit it being approximately the same size as the planet.
As it is poorly lit, observing it with the naked eye is impossible. Not even the brightest aurorae ever recorded can aid it from that perspective. Despite its impressive mass, it cannot fuse hydrogen at its core as a star would. But the aurorae point towards the existence of magnetic fields that would bring the celestial body closer to planets than to stars.
Also, it could be the existence of another planet in the deep magnetic field, but unobserved so far that sparks the aurorae. In combination with the rapid rotation of the brown dwarf, the aurorae lit up the celestial body.
The exciting discovery is explained in detail in the study featuring in the journal Nature.
Photo Credits bbc.co.uk