WISE 1828+2650, the coldest brown dwarf known so far, is denoted by a green dot in very center of this infrared image. The chilly star-like body isn't even as warm as a human body, at less than about 26 degrees Celsius.
Credit: NASA/JPL-Caltech/UCLA
This artist's conception illustrates what a 'Y dwarf' might look like. Y dwarfs are the coldest star-like bodies known, with temperatures that can be even cooler than the human body.
Credit: NASA/JPL-Caltech
This artist's conception illustrates what brown dwarfs of different types might look like to a hypothetical interstellar traveler who has flown a spaceship to each one. Brown dwarfs are like stars, but they aren't massive enough to fuse atoms steadily and shine with starlight - as our Sun does so well.
Credit: NASA/JPL-Caltech
MARYLAND: Six star-like bodies with temperatures as cool as the human body have been discovered after more than a decade of hunting.
When viewed with a visible-light telescope, these 'Y dwarfs' are nearly impossible to see. NASA's Wide-field Infrared Survey Explorer's (WISE) infrared vision allowed the telescope to finally spot their faint glow. The Y dwarfs relatively close to our Sun, within a distance of about 40 light-years.
"WISE scanned the entire sky for these and other objects, and was able to spot their feeble light with its highly sensitive infrared vision," said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington.
"They are 5,000 times brighter at the longer infrared wavelengths WISE observed from space than those observable from the ground."
Moving out of the kitchen
The Y's are the coldest members of the brown dwarf family. Brown dwarfs are sometimes referred to as 'failed' stars. They are too low in mass to fuse atoms at their cores and thus don't burn with the fires that keep stars like our Sun shining steadily for billions of years. Instead, these objects cool and fade with time, until what little light they do emit is at infrared wavelengths.
Astronomers study brown dwarfs to better understand how stars form, and to understand the atmospheres of planets beyond our Solar System. The atmospheres of brown dwarfs are similar to those of gas-giant planets like Jupiter, but they are easier to observe because they are alone in space, away from the blinding light of a parent star.
So far, WISE data have revealed 100 new brown dwarfs. More discoveries are expected as scientists continue to examine the enormous quantity of data from WISE.
"The brown dwarfs we were turning up before this discovery were more like the temperature of your oven," said Davy Kirkpatrick, a WISE science team member at the Infrared Processing and Analysis Centre at Caltech and lead author of a paper in the Astrophysical Journal Supplement Series. "With the discovery of Y dwarfs, we've moved out of the kitchen and into the cooler parts of the house."
Hidden house on our block
The Y dwarfs are in our Sun's neighborhood, from approximately nine to 40 light-years away. One dwarf is approximately nine light-years away, WISE 1541-2250, and may become the seventh closest star system, bumping red dwarf star Ross 154 back to eighth. By comparison, the star closest to our Solar System, Proxima Centauri, 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 the Jet Propulsion Laboratory in California. "It's thrilling to me to know we've got neighbours out there yet to be discovered."
Once the team identified brown dwarf candidates, they turned to NASA's Spitzer Space Telescope to narrow their list. To definitively confirm them, they used some of the most powerful telescopes and spectrometers on Earth to split apart the objects' light and look for telltale molecular signatures of water, methane and possibly ammonia.
Illuminated
How the heck can something with that temperature radiate visible light?
Please explain this to me. Last time I checked object as cold as the human body tend to be rather dark in the dark.