Brown dwarf stars host powerful aurora displays, astronomers discover

July 29, 2015
Artist's impression of the aurorae on the brown dwarf LSR J1835+3259. Credit: Chuck Carter and Gregg Hallinan/Caltech

Brown dwarf stars host powerful aurora displays just like planets, astronomers have discovered.

The so-called failed stars, which are difficult to detect and also remain hard to classify, are too massive to be planets but physicists from the Universities of Sheffield and Oxford have revealed that they host powerful auroras just like Earth.

The international team of researchers made the discovery by observing a brown dwarf 20 light years away using both radio and optical telescopes. Their findings provide further evidence that suggests these stars act more like supersized planets.

Dr Stuart Littlefair, from the University of Sheffield's Department of Physics and Astronomy, 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".

"We already know that brown dwarfs have cloudy atmospheres - like planets - although the clouds in brown dwarfs are made of minerals that form rocks on Earth now we know host powerful auroras too."

He added: "Sometimes the best thing about a scientific result is simply the thrill of discovering something exciting and cool. The northern lights on Earth are one of the most spectacular and beautiful things you can see.

Artist's impression of the aurorae on the brown dwarf LSR J1835+3259. Credit: Chuck Carter and Gregg Hallinan/Caltech

"I've always wanted to see them, but have never got the chance. It's particularly ironic that I got to discover an auroral light show which is vastly more powerful and many light years away!"

Auroral displays result when charged particles manage to enter a planet's magnetic field. Once within the magnetosphere, those particles get accelerated along the planet's magnetic field lines to the planet's poles where they collide with gas atoms in the atmosphere, producing the bright emissions associated with auroras.

During the study the international research team, led by Professor Gregg Hallinan from the California Institute of Technology, conducted an extensive observation campaign of a brown dwarf called LSRJ1835+3259.

The team used the most powerful radio telescope in the world, the National Radio Astronomy Observatory's Karl G. Jansky Very Large Array (JVLA) in New Mexico, as well as including Palomar's Hale Telescope and the W.M Keck Observatory's telescopes to make their ground breaking observations.

Using the JVLA they detected a bright pulse of radio waves that appeared as the brown dwarf rotated around. The object rotates every 2.84 hours, so the team were able to watch nearly three full rotations over the course of a single night.

The astronomers worked with the Hale Telescope and observed the brown dwarf varied optically on the same period as the radio pulses. The team found that the object's brightness varied periodically, indicating that there was a bright feature on the brown dwarf's surface. Dr Garret Cotter, from the University of Oxford, who also took part in the study said: "It was incredibly exciting to track the optical light form the aurora during the night with the Hale Telescope in California, one of the most venerable telescopes in the world, while simultaneously tracking the radio emission with the JVLA, one the world's newest radio telescopes."

Finally, the researchers used the Keck telescopes to precisely measure the brightness of the brown dwarf over time which was no simple feat given that these objects are extremely faint, many thousands of times fainter than our own Sun. The astronomers determined that the bright optical feature was likely to be caused by electrons hitting the hydrogen-dominated atmosphere of the brown dwarf to produce auroras.

The findings from the study, published in the journal Nature offer astronomers a convenient stepping stone for further study into exoplanets, planets orbiting stars other than our own sun.

Dr Cotter said: "In science, new knowledge often challenges our understanding. We know how controversial the situation was with Pluto, where astronomers had to look hard to try to decide if it is fundamentally one of the major planets of the solar system, or the first of the Kuiper Belt objects. Now, up at the other end of the size scale, we are challenged by seeing objects that traditionally would have been classified as stars, but seem to be showing more and more properties that make them look like super-sized ."

Explore further: Brown Dwarfs Beaming Like Pulsars

More information: Nature, DOI: 10.1038/nature14619

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17 comments

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rossim22
1.7 / 5 (6) Jul 29, 2015
The electrical interpretation of star formation does such a better job explaining why we should expect to see powerful aurora on 'failed stars' or red dwarfs.
carlo_piantini
1 / 5 (4) Jul 29, 2015
Well damn...this is really interesting. On the one hand, the demonstration of aurora *is* clearly planetary activity, if it's assumed that Birkeland currents are exclusively intra-solar system phenomena - they only flow *from* the Sun *to* the planets, and there is no galactic scale Birkeland currents interacting with the Sun itself.

But then you've got this: http://phys.org/n...tml#nRlv

Brown dwarfs behaving like stars again, and likewise, behaving similarly to galaxies - unless there is a profound difference between the jets being described in the link and the kind emitted from galactic centers.

Gotta love it when more electromagnetic phenomena is discovered in space!
carlo_piantini
1 / 5 (4) Jul 29, 2015
You're thinking like I'm thinking rossim. Both the aurora and the jets recently discovered are electrical phenomena, which should simply help prove the point that jets emanating from galactic centers are *likewise* caused by the flow of electric currents - which shouldn't be surprising, given the recent discovery from Herschel of helically-shaped magnetic field lines wrapping around spiral arms and moving inward toward the center. - http://phys.org/n...tml#nRlv

Unless the plasma of a galaxy is a superconductor, those field lines aren't frozen-in. Meaning that they're definitely being formed from some kind of current - either a Birkeland current or some other kind. This is why as an amateur astronomer, I'm really interested in Alfven's ideas. No, they probably aren't 100% right (historically they never were), but they are definitely working in the right direction.
bschott
1 / 5 (3) Jul 29, 2015
Carlo, check out the Ulysses solar probe data sometime. The thermal profile of the poles, the particle flow data and where all the helium concentrations are. Then imagine what the solar model was when they reviewed that data and how what they were seeing must have made them feel. A whole team of scientists coming to the realization that the real thing is almost nothing like the model.

A Birkland current is any current following a magnetic field "line" (god I hate that description), they don't generate the line they follow. If the sun wasn't as bright across the spectrum as it is, it would have aurorae as well.
carlo_piantini
1 / 5 (4) Jul 29, 2015
@bschott: Once my mathematics skills are up-to-par, my first order of business is rigorously going over all of the data taken in by the multitude of space-crafts we've sent out into space in the last ~70 years, beginning with Ulysses and the Voyager crafts.

Could you tell me a bit more about what you're talking about? Particularly the particle flow data? Did it strongly resemble the same flow/temperature profile that we see in our own aurora, and can you provide me with any references or links to the data?
bschott
1 / 5 (4) Jul 29, 2015
I will see what I can find. I have a colleague who has an extensive folder of original releases that all the creative googling one can do will not get you. It's actually strange because some of his downloads have been removed from the sites where he obtained them.
carlo_piantini
1 / 5 (2) Jul 29, 2015
I'd really, really appreciate it, and likewise, I find that particularly bizarre. That said, if I can't corroborate the information with any other source, I will have to take with a grain of salt, simply for the sake of healthy skepticism. I hope you understand. Likewise, would I be able to find the critical information about particle flow at the poles anyway, or are you saying that this info can't be found anymore?

My email is: carlo.piantini@gmail.com, if you'd like to send me anything you can find there. Not sure if you'd be able to provide it here of PO. Thanks!
wduckss
not rated yet Jul 29, 2015
Original article (and science today), the more it tends to brown dwarf is a big planet, not a star yet. This is also the a new realistic thinking (http://www.nature....18048). No mention of "failed" stars.
I would agree with Carlo_piantini, that this is a geological activity and not about Aurora, because missing of radiation or is definition of auroras incorrect.
HannesAlfven
1 / 5 (5) Jul 29, 2015
I really enjoy seeing authentic discussions about electrical cosmology, but it should be emphasized for people who are not so tuned into these ideas why brown dwarfs matter so much ...

There are certain types of brown dwarfs, it has been pointed out, which appear to have all of the key ingredients for life:

... water in their atmospheres

... diffuse electrical atmospheres

... and the part which the conventional theorists have not tuned into just yet is that they have these really puffed-out diffuse electrical atmospheres.

What the mainstream is not quite latching onto yet is that PLANETS CAN POTENTIALLY ORBIT WITHIN THESE ILLUMINATED PLASMA ENVELOPES.

You guys need to think carefully about the implications of that ...

No seasons.

No nights.

Possibly only marginal variation in temperatures.

Brown dwarfs are the best candidates for the origin of life we've seen to-date, some better than others, of course.
Enthusiastic Fool
5 / 5 (2) Jul 30, 2015
From the Nature preview:
we report simultaneous radio and optical spectroscopic observations of an object at the end of the stellar main sequence, located right at the boundary between stars and brown dwarfs, from which we have detected radio and optical auroral emissions both powered by magnetospheric currents. Whereas the magnetic activity of stars like our Sun is powered by processes that occur in their lower atmospheres, these aurorae are powered by processes originating much further out in the magnetosphere of the dwarf star that couple energy into the lower atmosphere


I am confused. Is there an expert around? The summary says it's on the end of the main sequence and refers to it as a dwarf star but the commentary in the article and the article title indicates that it's a brown dwarf. I wish I had the full paper.
Brown Dwarfs not main sequence?
https://en.wikipe...wn_dwarf
Main Sequence Dwarf Stars
https://en.wikipe...sequence
wduckss
1 / 5 (3) Jul 30, 2015
On the way to becoming the solar body, ... Jupiter and Earth, will become two types of brown dwarfs. At first it was not life as opposed to the other.
Part dwarfs orbiting a star (they can have the aurora), is part of the central body... It is important that a large variety of bodies in the universe can not identify with 2 or 3 types, each body is characteristic and different from the other, we see this in the solar system.
One should always examine statements that have no basis in fact confirmed in our system.
TechnoCreed
5 / 5 (4) Jul 30, 2015
@Enthusiastic Fool
I am confused. Is there an expert around?
With the continuous turd class discussions taking place on Physorg, why would you expect any expert to hang around? Would the answer of what is called here a main stream science amateur be good enough for you?

On the Wiki link (you gave) on brown dwarfs click on 3.1.1 you can read:
'Classification of brown dwarfs
Spectral Class M: There are brown dwarfs with a spectral class of M6.5 or later. They are also called late-M dwarfs.' https://en.wikipe..._class_M

Cont.
TechnoCreed
5 / 5 (4) Jul 30, 2015
...
This brown dwarf's spectral type is M8.5. Here is an early survey of this object. http://www.academ..._the_Sun
Here is an article on the same subject on space.com http://www.space....tem.html
And finally here is the paper you want to read: http://www.nature...DZreb-Qt
Enthusiastic Fool
5 / 5 (4) Jul 31, 2015
Thanks TechnoCreed.
Your answer was as good as can be expected. Good find on the links. I too lament the lack of expertise around here. It's quite a chore to keep up with the high density of "alternate science" posts here and it's not exactly civil discourse either.
Enthusiastic Fool
not rated yet Jul 31, 2015
I have a question in regards to the radio emission's correlation with aurora:
Is the source of the radio signal the aurora or is it deeper in the celestial body? I know radio of the Northern Lights can be picked up on Earth in the higher latitudes. Is the radio in this article analogous to picking up Earth's aurora or is this a larger phenomenon unique to gas giants?
jonesdave
4 / 5 (4) Jul 31, 2015
Amazing how they have actually managed to see this electrical activity from such a distance. Fair play. Strange that they can't actually see the alleged electric currents that are supposed to be powering the Sun in this solar system. Very weird.
rossim22
1 / 5 (1) Aug 02, 2015
Amazing how they have actually managed to see this electrical activity from such a distance. Fair play. Strange that they can't actually see the alleged electric currents that are supposed to be powering the Sun in this solar system. Very weird.


Strange how scientists cannot observe the electric currents which connect the earth to the Sun and are known to exist (against early predictions) as they power the aurora. Very weird.

So, to produce the aurora on earth, you need electric currents from the Sun... but this "failed star" can produce much stronger aurora... without electric currents? Very weird.

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