“Weather on Other Worlds” is an observation program that uses the Spitzer Space Telescope to study brown dwarfs. So far 44 brown dwarfs have fallen under its purview as scientists try to get a read on the conditions found on these ‘failed stars,’ which are too cool to sustain hydrogen fusion at their core. The variation in brightness between cloud-free and cloudy regions on the brown dwarf gives us information about what researchers interpret as torrential storms, and it turns out that half of the brown dwarfs investigated show these variations.
Given the chance nature of their orientation, this implies that most, if not all, brown dwarfs are wracked by high winds and violent lightning. The image below could have come off the cover of a 1950’s copy of Astounding, though there it would have illustrated one of Poul Anderson’s tales with Jupiter as a violent backdrop (“Call Me Joe” comes to mind). Brown dwarfs are, of course, a much more recent find, and in many ways a far more fascinating one.
Image: This artist’s concept shows what the weather might look like on cool star-like bodies known as brown dwarfs. These giant balls of gas start out life like stars, but lack the mass to sustain nuclear fusion at their cores, and instead, fade and cool with time. Credit: NASA/JPL-Caltech/University of Western Ontario/Stony Brook University.
Storms like these inevitably suggest Jupiter’s Great Red Spot, too, but we want to be careful with analogies considering how much we still have to learn about brown dwarfs themselves. What we can say is this: Brown dwarfs are too hot for water rain, leading most researchers to conclude that any storms associated with them are made up of hot sand, molten iron or salts.
The idea that brown dwarfs have turbulent weather is not surprising, but it is interesting to learn that such storms are evidently commonplace on them. Even more interesting is what the Spitzer work has revealed about brown dwarf rotation. Some of the Spitzer measurements found rotation periods much slower than any previously measured. Up to this point the assumption had been that brown dwarfs began rotating quickly shortly after they formed, a rotation that did not slow down as the objects aged. Aren Heinze (Stony Brook University) had this to say:
“We don’t yet know why these particular brown dwarfs spin so slowly, but several interesting possibilities exist. A brown dwarf that rotates slowly may have formed in an unusual way — or it may even have been slowed down by the gravity of a yet-undiscovered planet in a close orbit around it.”
Whatever the case, brown dwarfs do seem to be opening a window into weather systems in exotic places, systems that can be studied and characterized by their variations in brightness. Heinze presented this work at the 223rd annual meeting of the American Astronomical Society in Washington for principal investigator Stanimir Metchev (University of Western Ontario).