European astronomers led by Dr Federico Marocco from the University of Hertfordshire have discovered a brown dwarf with unusually red skies.

Brown dwarfs are too big to be considered as planets; yet they do not have sufficient material to fuse hydrogen in their cores to fully develop into stars. Sometimes described as failed stars, they are midway in mass between stars, like our Sun, and giant planets, like Jupiter and Saturn.

Using ESO’s Very Large Telescope in Chile and an innovative data analysis technique, Dr Marocco’s team detected a very thick layer of clouds in the upper atmosphere the brown dwarf ULAS J222711-004547.

“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. 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,” Dr Marocco said.

The giant planets of the Solar System, like Jupiter and Saturn, show various cloud layers including ammonia and hydrogen sulfide as well as water vapor.

The atmosphere observed in ULAS J222711-004547 is hotter – with water vapor, methane and probably some ammonia but, unusually, it is dominated by clay-sized mineral particles.

Getting a good understanding of how such an extreme atmosphere works will help us to better understand the range of atmospheres that can exist.

“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 Dr Avril Day-Jones from the University of Hertfordshire, who is a co-author of the paper published in the Monthly Notices of the Royal Astronomical Society (arXiv.org).

“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.”

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F. Marocco et al. The extremely red L dwarf ULAS J222711−004547 – dominated by dust. MNRAS, published online February 5, 2014; doi: 10.1093/mnras/stt2463