Stormy Weather: Brown Dwarf Star Could Model Extra-Solar Planet Atmosphere

Astronomers have observed extreme brightness changes on a nearby brown dwarf that may indicate a storm grander than any seen yet on a planet. This finding could new shed light on the atmospheres and weather on extra-solar planets. Credit: Art by Jon Lomberg.

Thanks to the help of the infrared camera on the 2.5m telescope at Las Campanas Observatory in Chile, astronomers are taking a very close look at a brown dwarf star named 2MASS J2139. During a recent survey they noticed something a little bit peculiar about this transitional solar system entity. Not only does it lay somewhere in-between being a dwarf star or a large planet – but it would appear to have a form of weather. Apparently there’s no place to escape clouds!

A University of Toronto-led team of astronomers had been doing a survey of nearby brown dwarfs, when they noticed that one in particular changed brightness in a matter of hours – the largest variation observed so far.

“We found that our target’s brightness changed by a whopping 30 per cent in just under eight hours,” said PhD candidate Jacqueline Radigan, lead author of a paper to be presented this week at the Extreme Solar Systems II conference in Jackson Hole, Wyoming and submitted to the Astrophysical Journal. “The best explanation is that brighter and darker patches of its atmosphere are coming into our view as the brown dwarf spins on its axis,” said Radigan.

The team quickly took into account all possibilities for the differences in magnitude – from the possibility of a binary companion to cool magnetic spots – but none of these answers were likely. What could be causing this difference in brightness that seemed to be rotational?

“We might be looking at a gigantic storm raging on this brown dwarf, perhaps a grander version of the Great Red Spot on Jupiter in our own solar system, or we may be seeing the hotter, deeper layers of its atmosphere through big holes in the cloud deck,” said co-author Professor Ray Jayawardhana, Canada Research Chair in Observational Astrophysics at the University of Toronto and author of the recent book Strange New Worlds: The Search for Alien Planets and Life beyond Our Solar System.

Using computer modeling, astronomers can hypothesize what may be going on as silicates and metals mix over a variety of temperatures. The result is a condensate cloud. Thanks to 2MASS J2139′s variability, we’re able to observe what may be evolving “weather patterns”. These models may one day help us to extrapolate extra-solar giant planet weather conditions.

“Measuring how quickly cloud features change in brown dwarf atmospheres may allow us to infer atmospheric wind speeds eventually and teach us about how winds are generated in brown dwarf and planetary atmospheres,” Radigan added.

Original Story Source: University of Toronto News. For Further Reading: High Amplitude, Periodic Variability of a Cool Brown Dwarf: Evidence for Patchy, High-Contrast Cloud Features.

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