Brown Dwarf with Bizarre Red Atmosphere Spotted by ESO's Very Large Telescope

From the Atacama Desert in northern Chile, the European Southern Observatory's Very Large Telescope has spotted a distant brown dwarf with an unusual red atmosphere.

Brown dwarfs are peculiar celestial bodies, too big to be classified as planets yet lacking the material to fully fuse hydrogen in their cores to form into proper stars. They are cold, faint space objects that do not produce heat at their cores. (Brown dwarfs are often called failed stars.)

Astronomers from the University of Hertfordshire's Centre for Astrophysics Research used the VLT to spot the odd brown dwarf, which is extremely red compared to "normal" brown dwarfs, and further investigate its puzzling hue.

Writing in the journal Monthly Notices of the Royal Astronomical Society, lead astronomer Federico Marocco reports that the brown dwarf, officially recognized as ULAS J222711-004547, is red because of an unusually thick layer of clouds in its upper atmosphere.

"These are not the type of clouds that we are used to seeing on Earth. The thick clouds on this particular brown dwarf are mostly made of mineral dust, like enstatite and corundum," Marocco said. "Not only have we been able to infer their presence, but we have also been able to estimate the size of the dust grains in the clouds."

The red sky of the brown dwarf suggests that the atmosphere there is loaded with moisture and packed with clay-sized grains of dust.

"If our morning skies are red, it is because clear skies to the east permit the Sun to light the undersides of moisture-bearing clouds coming in from the west," the researchers said in a statement. "Conversely, in order to see red clouds in the evening, sunlight must have a clear path from the west in order to illuminate moisture-bearing clouds moving off to the east."

For the new brown dwarf, however, the atmospheric conditions there create a scenario where the sky is always red.

By observing the red brown dwarf's atmospheric conditions, astronomers hope to better understand how the extreme conditions there came to be and how a range of similarly extreme atmospheres can exist throughout the universe.

"Being one of the reddest brown dwarfs ever observed, ULAS J222711-004547 makes an ideal target for multiple observations to understand how the weather is in such an extreme atmosphere," said Hertfordshire astronomer Avril Day-Jones.

"By studying the composition and variability in luminosity and colors of objects like this, we can understand how the weather works on brown dwarfs and how it links to other giant planets," she said.