Are Coldest Brown Dwarfs Star-Planet Hybrids?

Astronomers from the Harvard-Smithsonian Center for Astrophysics conducted a study on brown dwarfs and found that they can be classified as stars as well as planets.

The brown dwarfs were first spotted with the help of NASA's WISE space telescope about two years ago. The exact temperature of their surface has been a mystery with some data even suggesting that the stars could have room temperatures.

But this recent study concludes that these brown dwarfs, also known as failed stars, which were labeled as the coldest known celestial bodies, are hotter with temperatures of  250-350 degrees Fahrenheit. The gravitational contraction of these bodies is said to be their sole source of energy. They take over a billion years to cool down and attain low temperatures and these bodies are said to weigh about five to 20 times of Jupiter's mass.

"If one of these objects was found orbiting a star, there is a good chance that it would be called a planet," stated Trent Dupuy, a Hubble Fellow at the Harvard-Smithsonian Center for Astrophysics.

 But because they probably formed on their own and not in a proto-planetary disk, astronomers still call these objects brown dwarfs even if they are "planetary mass."

These dwarfs are still not confirmed to be planets or stars as they contain a bit of both qualities. They emanate a faint light at infrared wavelengths because of their low temperature and small size.  

The astronomers used NASA's Spitzer Space Telescope to verify the exact temperature and luminosity of the brown dwarfs situated at a distance of 20 to 50 light-years from Earth.

The researchers need to know the exact distance of these brown dwarfs in order to obtain accurate temperatures. They tried establishing a link between the proximity of the brown dwarfs along with their temperature and brightness.

"To be able to determine accurate distances, our measurements had to be the same precision as knowing the position of a firefly to within 1 inch from 200 miles away," explains Adam Kraus, professor at the University of Texas at Austin and the other author of the study.

The new information created doubts in the minds of astronomers as the properties of these warm starts did not seemed to be linked with temperatures, contrary to other warmer brown dwarfs. Other factors like the chemical composition of the surface and the convective mixing appear to play major roles in altering the properties of these bodies.

 The data used for analysis in this research consisted of the early samples of the coldest brown dwarfs accumulated by WISE survey data. The remaining data collected over the past two years is yet to be observed, which might solve the mystery of these issues.