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Astronomers find extreme weather on an alien world

September 12, 2011

Cosmic oddball may harbour a gigantic storm

TORONTO, ON – 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,” 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.

“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.

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 added.

The paper describ­ing the find­ings, titled High Ampli­tude, Peri­od­ic Vari­abil­i­ty of a Cool Brown Dwarf: Evi­dence for Patchy, High-Con­trast Cloud Fea­tures, is avail­able online now.

Oth­er co-authors of this work are David Lafrenière and Éti­enne Arti­gau at the Uni­ver­sité de Mon­tre­al, Didi­er Saumon at Los Alam­os Nation­al Lab­o­ra­to­ry, and Mark Mare­ly at NASA Ames Research Cen­ter.

The research was sup­port­ed by a Vanier Cana­da Grad­u­ate Schol­ar­ship award­ed to Radi­gan, and a Research Tools and Instru­men­ta­tion grant, a Dis­cov­ery grant, a Stea­cie Fel­low­ship and the Cana­da Research Chairs pro­gram, all award­ed to Jayaward­hana from the Nat­ur­al Sci­ences and Engi­neer­ing Research Coun­cil of Cana­da.

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For more infor­ma­tion, please con­tact:

Jacque­line Radi­gan
Depart­ment of Astron­o­my and Astro­physics
Uni­ver­si­ty of Toron­to
415–812-2229 © from Sept. 12–17

Ray Jayaward­hana
Depart­ment of Astron­o­my and Astro­physics
Uni­ver­si­ty of Toron­to
857–334-3406 ©

Sean Bet­tam
Com­mu­ni­ca­tions, Fac­ul­ty of Arts & Sci­ence
Uni­ver­si­ty of Toron­to