Star of Extreme Colors is Cool
Astronomers discover cool stars in nearby space
What has excited astronomers are its very peculiar colors, which actually make it appear either very blue or very red, depending on which part of the spectrum is used to look at it.
The object is known as SDSS 1416+13B and it is in a wide orbit around a somewhat brighter and warmer brown dwarf, SDSS 1416+13A. The brighter member of the pair was detected in visible light by the Sloan Digital Sky Survey. By contrast, SDSS 1416+13B is only seen in infrared light. The pair is located between 15 and 50 light-years from the solar system, which is quite close in astronomical terms.
“We have to be a bit careful about this one because its colors are so different than anything seen before that we don’t really understand it yet. Even if it turns out that the low temperature is not quite record breaking, the colors are so extreme that this object will keep a lot of physicists busy trying to explain it.”
SDSS 1416+13B was first noticed by Dr. Ben Burningham of the University of Hertfordshire as part of a dedicated search for cool brown dwarfs in the UKIRT Infrared Deep Sky Survey (UKIDSS). The object appeared far bluer at near infrared wavelengths than any brown dwarf seen before. A near infrared spectrum taken with the Japanese Subaru Telescope in Hawaii showed that it is a type of brown dwarf called a T dwarf, which has a lot of methane in its atmosphere, but with peculiar features including a big gap at certain wavelengths.
“The fact that it is a binary companion to a warmer brown dwarf that also has an unusual spectrum is helping us to fill in some gaps in our understanding”, says Dr. Burningham. “It seems likely that both brown dwarfs are somewhat poor in heavy elements. This can be explained if they are very old, which also fits with the very low temperature of the faint companion.”
Too small to be stars, brown dwarfs have masses smaller than stars but larger than gas giant planets like Jupiter. Due to their low temperature these objects are very faint in visible light, and are detected by their glow at infrared wavelengths. They were originally dubbed “brown dwarfs” long before any were actually discovered, to describe the idea of bodies that were cooler, fainter and redder than red dwarf stars, with the color brown representing the mix of red and black.