Brown dwarfs are not quite stars. Some aspects of them resemble planets, like the fact that they have their own versions of “northern lights,” which can be seen from very far away. One of these distant auroras has been captured in the video above

One of the major benefits to living on the Earth is shelter from cosmic rays. Cosmic rays are small charged particles hurtling through the universe. When they hit the Earth’s magnetosphere, they tend to get channeled towards the poles. The gas molecules they hit along the way, especially as they’re spiraling near the pole, start glowing. We see this glow, from below, as auroras—otherwise known as the northern or southern lights.


Through a radio-telescope, we can see other planet’s auroras as well. What we see pulsing above is not a planet, though. It’s a brown dwarf. When material condenses, due to gravity, it heats. Enough material squeezing tightly enough will initiate the fusion of hydrogen, turning what was a ball of gas into a star. When there isn’t quite enough material to start fusion, the would-be star is considered a brown dwarf. There are all kinds of brown dwarfs at many different temperatures—one of them isn’t even hot enough for water to boil on its surface.

But what’s the difference between brown dwarfs and regular planets? That’s a question that a lot of scientists are debating. Brown dwarfs have some characteristics that make them seem like stars and some that make them seem like planets. These auroras are pushing them more towards the planet end of the spectrum.


[Source: Magnetospherically driven optical and radio aurorae at the end of the main sequence]

Video:Stephen Bourke/Caltech. Image: Chuck Carter and Gregg Hallinan/Caltech.