Brown dwarfs are curious objects. Although they can weigh up to 80 Jupiter masses, they are too small to be called stars yet too big to be called planets. Until the late 1980′s they were purely theoretical objects.
However, as our observational capabilities improved - allowing astronomers to look deeper into space, detecting cooler objects - many of these "failed stars" (or could they be called "successful planets"?) were found to be floating around our galaxy.
Now a team of astronomers, using the United Kingdom Infrared Telescope (UKIRT) in Hawaii, may have spotted the coolest brown dwarf yet.
"This looks like being the fourth time in three years that the UKIRT has discovered made a record breaking discovery of the coolest known brown dwarf, with an estimated temperature not far above 200 degrees Celsius," said Dr Philip Lucas at the University of Hertfordshire's School of Physics, Astronomy and Mathematics, UK.
200 degrees Celsius (or nearly 400 degrees Fahrenheit) is only twice as hot as the cup of tea I have cooling on my desk, so it is little wonder brown dwarfs are known as "sub-stellar" objects. (For an object to be "stellar," it needs to be a star, burning fuel through nuclear fusion. Brown dwarfs are too small to do this for long periods of time.)
The previous "Coolest Sub-Stellar Object" prize went to a brown dwarf called Wolf 940B, located 40 light years from Earth. Wolf 940B was measured to have a surface temperature of 300 degrees Celsius by Australian astronomers.