Stars are supposed to be hot stuff. But would you believe astronomers have just
discovered a class of stars as cool as — well — as cool as you are? They're
called "Y Dwarfs".
A NASA space telescope named WISE made the discovery. WISE is short for
"Wide-field Infrared Survey Explorer." It's an infrared observatory whose
recently concluded mission was to scan the heavens at wavelengths the human eye
WISE recently found six incredibly cool stars less than 40 light years from
Earth. One of these Y dwarfs, WISE 1828+2650, is the record holder for
stellar-cool with an estimated atmospheric temperature less than 80 degrees
Fahrenheit (25 degrees Celsius). WISE 1828+2650 is a room temperature star!
Other Y dwarfs were about the same temperature as a human body. How can a star
be so cool?
The Y's are the chilliest members of the brown dwarf family. Brown dwarfs are
sometimes referred to as "failed" stars. They are more massive than planets, yet
not quite massive enough to fuse atoms in their cores.
Brown dwarfs do not burn with the inner nuclear fires that keep stars like our
sun shining steadily for billions of years. Without fusion to keep them going,
brown dwarfs cool and fade with time, until what little light they do emit is at
infrared wavelengths perfect targets for a telescope like WISE.
"WISE scanned the entire sky for these and other objects, and was able to spot
their feeble light with its highly sensitive infrared vision," says William
Danchi, WISE Program Scientist at NASA Headquarters in Washington, DC.
If an astronaut could visit one of these stars, they would probably find a
lonely sphere of gas that looks a lot like Jupiter only bigger.
Make that a big purple Jupiter.
Researchers suspect that molecules in the atmosphere of Y Dwarfs give the stars
a purple or magenta color. No one knows for sure, though, because WISE can only
see these faint stars as distant pinpricks of infrared light.
Future space travelers might consider a visiting Y Dwarfs for a closer look. At
a distance of less than 40 light years, these stars are relatively nearby.
"Finding these objects so close to our sun is like discovering there's a hidden
house on your block that you didn't know about," says Michael Cushing, a WISE
team member at the Jet Propulsion Laboratory.
"It's thrilling to me to know we've got neighbors out there and maybe more yet
to be discovered. With WISE, we may even find a brown dwarf closer to us than
the closest known star, Proxima Centauri."
Now that would be pretty cool news.
For more information about stars, hot and cold, visit, science.nasa.gov