The new aurora finding shows that these kinds of objects seem to have an odd mix of star and giant planet-like features. And the successful observation of the an aurora on this distant brown dwarf gives researchers hope of spotting them on distant exoplanets, too.
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Now, a new study is strengthening the “planet” argument.
Auroras, the radiant displays of colors in the sky known on Earth as the northern or southern lights, are also seen on all of the other planets with magnetic fields in the solar system.
But particles from the sun aren’t necessary for auroras to exist; Jupiter’s auroras are caused by particles that come from the planet’s many moons. The light they illuminate is so dim, it can only be observed in the infrared.
While in graduate school, in 2006, Hallinan discovered that brown dwarfs can actually pulse at radio frequencies. Yet what really confuses astronomers is how small these stars are – landing somewhere between 15 and 75 times the mass of Jupiter. Image via Chuck Carter and Gregg Hallinan, Caltech.
“Sure enough, we saw it”, Hallinan said.
One way scientists have gone about answering this question is by studying the magnetic activity of brown dwarfs; magnetic fields manifest differently when surrounding a star versus a planet.
Here on Earth, auroras form when charged particles carried by stellar winds push through the planet’s atmosphere and collide with gas atoms at altitudes ranging from 90 to 300 kilometers (56 to 186 miles). Earth’s magnetic field, however, acts something like a shield from this solar activity.
British astronomer Dr Stuart Littlefair, a member of the team from the University of Sheffield, said: “Brown dwarfs span the gap between stars and planets and these results are yet more evidence that we need to think of brown dwarfs as beefed-up planets, rather than “failed stars”. Hallinan and his team were able to establish that this hydrogen emission is a signature of auroras near the surface of the brown dwarf.
According to a CNET article, it was not until 2001 that scientists discovered that brown dwarfs generate radio waves. Rather, they were reddish, like Jupiter’s – though far stronger, because the brown dwarf has a much stronger magnetic field than Jupiter does. These telescopes enabled the researchers to detect that the brown dwarf star, LSR J1835+3259, had auroras.
The astronomers observed the object, called LSR J1835+3259, using the Karl G.
While it can’t be seen with the naked eye, scientists believe it would appear bright red – in contrast to the dancing green, purple or blue light seen on Earth and produced by the interaction between sun’s solar winds and our planet’s magnetic field.
“All the magnetic activity we see on this object can be explained by powerful auroras”, Gregg Hallinan of the California Institute of Technology said in a release. In comparison, these newfound auroras are more than 10,000 times – and maybe 100,000 times – brighter than Jupiter’s, Hallinan said.
Finally, Hallinan and his colleagues used the Keck telescopes to measure precisely the brightness of the brown dwarf over time-no simple feat given that these objects are many thousands of times fainter than our own Sunday.
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The source of the aurora could also be totally new to us. But in the case of the brown dwarfs, the process of the electrons interacting with the hydrogen is what is more commonly seen around the larger planets in our solar system like Jupiter and Saturn. Burgasser was not involved with the Nature study.
