Monday, 26 February 2018

When do aging brown dwarfs sweep the clouds away?


Brown dwarfs, the larger cousins of giant planets, undergo atmospheric changes from cloudy to cloudless as they age and cool. A team of astronomers led by Carnegie's Jonathan Gagné measured for the first time the temperature at which this shift happens in young brown dwarfs. Their findings, published by the Astrophysical Journal Letters, may help them better understand how gas giant planets like our own Solar System's Jupiter evolved.

When do aging brown dwarfs sweep the clouds away?
Artist's conception of a different brown dwarf to the one studied by Jonathan Gagné and his team. The brown
dwarf depicted here is also part of a moving group, although a different one than AB Doradus
[Credit: NASA/JPL, slightly modified by Jonathan Gagné]
Brown dwarfs are too small to sustain the hydrogen fusion process that fuels stars and allows them to remain hot and bright for a long time. After formation, brown dwarfs slowly cool down and contract over time--at some point shifting from heavily cloud covered to having completely clear skies.

Because they are freely floating in space, the atmospheric properties of brown dwarfs are much easier to study than the atmospheres of exoplanets, where the light of a central star can be completely overwhelming.

In this paper, Gagné and his colleagues--Katelyn Allers of Bucknell University; Christopher Theissen of University of California San Diego; Jacqueline Faherty and Daniella Bardalez Gagliuffi of the American Museum of Natural History, and Etienne Artigau of Institute for Research on Exoplanets, Université de Montréal--focused on an unusually red brown dwarf called 2MASS J13243553+6358281, which they were able to determine is one of the nearest known planetary mass objects to our Solar System.

The redness of this object had previously been suggested to indicate that it was actually a binary system, but the research team's findings indicate that it is a single free floating planetary mass object.

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