Twin Brown Dwarfs at 6 light years. Ken Croswell @PhysicsWorld

May 27, 01:55 AM


(Photo:NASA/JPL-Caltech -

This artist's conception illustrates the brown dwarf named 2MASSJ22282889-431026. NASA's Hubble and Spitzer space telescopes observed the object to learn more about its turbulent atmosphere. Brown dwarfs are more massive and hotter than planets but lack the mass required to become sizzling stars. Their atmospheres can be similar to the giant planet Jupiter's. Spitzer and Hubble simultaneously observed the object as it rotated every 1.4 hours. The results suggest wind-driven, planet-size clouds. )

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Twin Brown Dwarfs at 6 light years. Ken Croswell @PhysicsWorld .

Cooler than the Sun

Brown dwarfs are much cooler than the Sun and therefore shine most profusely at infrared wavelengths. On 10 February 2013 Kevin Luhman of Pennsylvania State University was examining images from NASA’s Wide-field Infrared Survey Explorer (WISE) spacecraft when he discovered the nearest brown dwarf to Earth. It is so close that only two star systems are nearer: the triple-star Alpha Centauri, which is 4.4 light-years away; and Barnard’s Star, which is 6.0 light-years distant. Luhman then found that our new neighbour – named “Luhman 16” – is actually a couple: two brown dwarfs orbiting each other.

“Until now, all brown dwarfs were too far away and too faint,” says Ian Crossfield of the Max Planck Institute for Astronomy in Heidelberg, who led the team that has taken images of clouds on one of these brown dwarfs. “We just couldn’t study them in enough detail to resolve features on their surfaces.”

Because of its proximity, Luhman 16 boasts the brightest brown dwarfs that are known. They are about twice as far apart as Mars is from the Sun and orbit each other roughly every quarter century. Although similar in temperature – Luhman 16 A, the brighter one, is at 1500 K, whereas Luhman 16 B is at 1450 K – their atmospheres differ. Luhman 16 A’s light does not fluctuate, suggesting a featureless atmosphere. So Crossfield and colleagues focused their attention on Luhman 16 B, whose light does vary. Because the brown dwarf is in the southern constellation Vela, the researchers observed its near-infrared spectrum with the Very Large Telescope in Chile.