Last year, NASA announced that it had discovered 14 of the coldest stars it had ever recorded. The so-called "brown dwarfs" were, at that time, listed among the coldest known stars in our universe.
Now, employing the same instrumentation it used to detect last year's brown dwarfs, NASA has identified six new, even-cooler orbs known as "Y-dwarfs." Y-dwarfs are the coldest members of the brown dwarf family, which makes these stars the coolest of the cool. How cool you ask? Try cooler than the human body.
Brown dwarfs, and Y-dwarfs especially, are what astronomers often refer to as "failed stars;" the low density of these astral bodies prohibits them from fusing atoms at their cores, which in turn keeps them from burning with the enduring heat and intensity typical of other stars (our Sun, for example, has a surface temperature of around 10,000 Fahrenheit, a core temperature as high as 27 million degrees Fahrenheit, and will continue to burn for at least a few billion years).
But astronomers can still learn a lot from these stellar failures, so it's in their best interests to catalog as many of them as possible. Unfortunately, the same characteristics that make these brown dwarfs interesting to study makes them very difficult to find.
Because brown dwarfs lack the mass to keep burning for extended periods of time, they tend to gradually cool and fade, until the only light they emit is found at infrared wavelengths that are invisible to the human eye. In other words, searching for brown dwarfs with a visible-light telescope is damn near impossible. (The image up top is an artist's conception of what a Y-dwarf might look like.)
So how did NASA scientists find the dwarfs? Simple: they built an infrared telescope, and then they stuck it on a satellite. The combination satellite/telescope is called the Wide-field Infrared Survey Explorer, or WISE for short.
WISE's heat-and-IR-sensing capabilities are what allowed it to capture the infrared image pictured here (click to embiggen). The pale green dot at the very center of the photo is WISE 1828+2650, what NASA scientists are calling the record holder for the coldest brown dwarf ever discovered, with an estimated atmospheric temperature of less than 80 degrees Fahrenheit.
But what's really incredible about the discovery of WISE 1828+2650 and the other recently uncovered Y-dwarfs is their proximity to our own solar system. Some of the newly discovered Y dwarfs are a mere nine light years away (Proxima Centauri, the star closest to our solar system, is about four light-years away).
"Finding brown dwarfs near our sun is like discovering there's a hidden house on your block that you didn't know about," said Michael Cushing, a WISE team member at NASA's Jet Propulsion Laboratory. "It's thrilling to me to know we've got neighbors out there yet to be discovered. With WISE, we may even find a brown dwarf closer to us than [Proxima Centauri]."
All images via NASA/JPL