Planets Orbiting White or Brown Dwarfs Are Poor Candidates for Life

A new finding by a U.S. astronomer suggests that there is a very slim possibility of life on the extra solar planets, the white dwarf and the brown dwarf.

White dwarfs are basically what stars like our Sun become when they exhaust their nuclear fuel. As a star approaches the end of its nuclear burning stage, it expels most of its outer material until the hot core remains. Example of a white dwarf is 'Sirius B',  detected in 1862. 

A brown dwarf is a failed star. This star is of a size between that of a giant planet like Jupiter and a small star. It was from 1995 that astronomers were able to detect a few nearby brown dwarfs. All the brown dwarfs detected so far are parts of a binary system.

No terrestrial or Earth like planets have been confirmed orbiting these white and brown dwarfs but there is no valid evidence to support this, according to reports.

The new research, by Rory Barnes of the University of Washington and Rene Heller of Germany's Leibniz Institute for Astrophysics Potsdam, hints that planets orbiting white or brown dwarfs will prove poor candidates for life support.

He says both the white and brown dwarfs are bright enough to theoretically support a habitable zone. Because the swath of space is just right for an orbiting planet's surface water to be in liquid form, thus giving hints of supporting life.

The white and brown stars are different from the normal star sun. They slowly cool down and become less luminous over time. During this process, their habitable zones gradually shrink inward.

Because of their past, such planets would "face a difficult path to habitability, even if they're discovered right in that habitable zone" Barnes said.

"These planets, if we find them today in a current habitable zone, previously had to have gone through a phase which sterilized them forever," Barnes said. Heller added, "So, even if they are located in the habitable zone today, they are dead."

Barnes is the lead author of a paper published in November in the journal Astrobiology; and Heller is co-author.