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. Image: Jon Lomberg |
A University of Toronto-led team of astronomers has observed
extreme brightness changes on a nearby brown dwarf that may indicate a storm
grander than any seen yet on a planet. Because old brown dwarfs and giant
planets have similar atmospheres, this finding could shed new light on weather
phenomena of extra-solar planets.
As part of a large survey of nearby brown dwarfs—objects
that occupy the mass gap between dwarf stars and giant planets—the scientists used
an infrared camera on the 2.5m telescope at Las Campanas Observatory in Chile
to capture repeated images of a brown dwarf dubbed 2MASS J21392676+0220226, or
2MASS 2139 for short, over several hours. In that short time span, they
recorded the largest variations in brightness ever seen on a cool brown dwarf.
“We found that our target’s brightness changed by a
whopping 30 per cent in just under eight hours,” says PhD candidate
Jacqueline Radigan, lead author of a paper 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,” says Radigan.
“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,” says coauthor Professor
Ray Jayawardhana, Canada Research Chair in Observational Astrophysics at the
University of Toronto.
According to theoretical models, clouds form in brown dwarf
and giant planet atmospheres when tiny dust grains made of silicates and metals
condense. The depth and profile of 2MASS 2139’s brightness variations changed over
weeks and months, suggesting that cloud patterns in its atmosphere are evolving
with time.
“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 adds.
