Clouds on nearby brown dwarf mapped

Technique that revealed failed star’s weather could do the same for exoplanets

CLOUD COVER  Cloudy (dark) and clear (yellow) patches persist on the brown dwarf Luhman 16B as it rotates. Images show the failed star’s cloud layer in infrared wavelengths at roughly 48-minute intervals. 

I. Crossfield/European Southern Observatory

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One of the first maps of clouds on an object outside the solar system appears in the Jan. 30 Nature.

The clouds surround Luhman 16B, a brown dwarf just 6.5 light-years away in the constellation Vela. Brown dwarfs are gaseous objects larger than planets but too small to fuse hydrogen as true stars do. Previous studies hinted that brown dwarfs’ ultrahot atmospheres contain clouds of molten iron and silicates.

To see Luhman 16B’s clouds, a team led by Ian Crossfield of the Max Planck Institute for Astronomy in Heidelberg, Germany, used the Very Large Telescope in Chile.

The researchers gathered infrared light as Luhman 16B rotated on its axis. Darker areas indicated higher, colder clouds (but still hot enough to melt iron) and lighter patches indicated either lower, hotter clouds or hydrogen gas on the dwarf’s surface, visible through gaps in the upper layer. The team saw cloudy and clear patches lasting roughly five hours, which is the length of one day on Luhman 16B.

Because brown dwarfs are similar in composition to gas giants like Jupiter, Crossfield thinks his team’s technique will help astronomers interpret weather on planets circling distant stars.

Editor’s Note: This story was updated February 4, 2014, to correct the description of the infrared light collected and to correct the compounds suggested to exist in brown dwarf atmospheres.

CLOUDY DWARF  High clouds (dark patches) around brown dwarf Luhman 16B part to reveal gaps (yellow patches), in an animation of infrared light gathered from nearly one full rotation of the failed star. Credit: I. Crossfield/European Southern Observatory

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