As cool as the human body: Wise mission discovers coolest class of stars

Aug 24, 2011
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. Image credit: NASA/JPL-Caltech

(PhysOrg.com) -- Scientists using data from NASA's Wide-field Infrared Survey Explorer (WISE) have discovered the coldest class of star-like bodies, with temperatures as cool as the human body.

Astronomers hunted these dark orbs, termed Y dwarfs, for more than a decade without success. When viewed with a visible-light telescope, they are nearly impossible to see. WISE's infrared vision allowed the telescope to finally spot the faint glow of six 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 ," said Jon Morse, Astrophysics Division director at Headquarters in Washington. "They are 5,000 times brighter at the longer infrared wavelengths WISE observed from space than those observable from the ground."

The Y's are the coldest members of the brown dwarf family. 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.

NASA's Wide-field Infrared Survey Explorer, or WISE, has uncovered the coldest brown dwarf known so far (green dot in very center of this infrared image). Image credit: NASA/JPL-Caltech/UCLA

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 .

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 telescope performed the most advanced survey of the sky at to date, from Jan. 2010 to Feb. 2011, scanning the entire sky about 1.5 times.

Of the 100 brown dwarfs, six are classified as cool Y's. One of the Y dwarfs, called WISE 1828+2650, is the record holder for the coldest brown dwarf, with an estimated atmospheric temperature cooler than room temperature, or less than about 80 degrees Fahrenheit (25 degrees Celsius).

"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 Center at the California Institute of Technology in Pasadena, Calif. "With the discovery of Y dwarfs, we've moved out of the kitchen and into the cooler parts of the house."

Kirkpatrick is lead author of a paper appearing in the Astrophysical Journal Supplement Series, describing the 100 confirmed brown dwarfs. Michael Cushing, a WISE team member at NASA's Jet Propulsion Laboratory in Pasadena, Calif., is lead author of a paper describing the Y dwarfs in the Astrophysical Journal.

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. Image credit: NASA/JPL-Caltech

The Y dwarfs are in our sun's neighborhood, from approximately nine to 40 light-years away. The Y dwarf approximately nine light-years away, WISE 1541-2250, may become the seventh closest star system, bumping 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," Cushing said. "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 our closest known star."

Once the WISE team identified brown dwarf candidates, they turned to NASA's Spitzer Space Telescope to narrow their list. To definitively confirm them, the WISE team used some of the most powerful telescopes on Earth to split apart the objects' light and look for telltale molecular signatures of water, methane and possibly ammonia. For the very coldest of the new Y dwarfs, the team used NASA's Hubble Space Telescope. The Y dwarfs were identified based on a change in these spectral features compared to other brown dwarfs, indicating they have a lower atmospheric temperature.

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User comments : 18

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Thecis
5 / 5 (2) Aug 24, 2011
This is great. A whole bunch of mass that one couldn't see before. WIth (Y class) brown dwarfs, I wonder what the source of energy is? The mass is to small to ignite fusion but what powers this star type then? Do they just cool down as earth will do? Are they then to be classified as gas giants (as Jupiter) or "planets" instead of stars.

I wonder what its surface would look like. With some Y-class brown dwarfs it is nice and cosy with its almost room temperature.
Mayday
5 / 5 (1) Aug 24, 2011
It would be great to know the location in the sky of some of the closer ones. Any sources for that information? And of course these objects could have planets, right? And something akin to our own Oort cloud? It appears that there is a lot out there to run into.
EarthlingX
5 / 5 (4) Aug 24, 2011
Here are papers from arxiv.org :
The Discovery of Y Dwarfs Using Data from the Wide-field Infrared Survey Explorer (WISE)
http://arxiv.org/abs/1108.4678

and

The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE)
http://arxiv.org/abs/1108.4677

Enjoy :)
epsi00
3.9 / 5 (7) Aug 24, 2011
This is your dark matter secret.
Husky
4.5 / 5 (2) Aug 24, 2011
source of energy is radiactrive decay and friction from contracting gas, both will level off eventually
Yelmurc
3 / 5 (4) Aug 24, 2011
The universe is a amazing place. Who knows what we will find tomorrow.
Shootist
1.8 / 5 (5) Aug 24, 2011
Is there a hunk o' neutronium in the core of this almost star, Oliver?
krundoloss
3.3 / 5 (6) Aug 24, 2011
epsi - Spot on man. There is so much we dont know about the universe, we just have to accept that we cant complete the picture just yet, instead of making up stuff like Dark Energy.
Jaeherys
4.4 / 5 (14) Aug 24, 2011
@krundoloss
If dark matter and dark energy were renamed "missing mass particle(s) that are very faint or invisible" and the "weak repulsive force of the universe" would there be a difference of how people respond? Of course, because they don't sound "crazy" and from Star Trek. People get hung up on the names which are just arbitrary and at this point in time it's just childish.

Dark energy exists because we can see the universe being pushed apart which is a name given to a phenomenon with the mechanics of this push unknown (AFAIK). We could have named it Effect XityZed-1916 and there'd be no difference!

People just don't make this stuff up for shits and giggles, JESUS!
Jeddy_Mctedder
2 / 5 (4) Aug 24, 2011
what's the estimated mass of these y dwarfs? now the key is to look for things between Jupiter size and dwarf size.
jsdarkdestruction
3.7 / 5 (6) Aug 24, 2011
Jaeherys, It says i only gave you a 5 star rating but in my head you got a 50 star rating. Thank you, i get so tired of hearing people get hung up on the word dark and dont realize we say dark because like it suggests we are not completely aware of what it is, but it is an observable effect.
finitesolutions
1 / 5 (5) Aug 24, 2011
Jesus has been mentioned and maybe we name a star on his name and maybe all this idolatry over a convicted and executed roman criminal will cool down. regards.
yyz
5 / 5 (2) Aug 24, 2011
"what's the estimated mass of these y dwarfs? now the key is to look for things between Jupiter size and dwarf size."

See Table 6 (pg 26) of the paper on Y dwarfs for the masses (relative to Jupiter) of the new discoveries: http://arxiv.org/...78v1.pdf
Nik_2213
not rated yet Aug 24, 2011
Thanks for those links, folks !!
Quarl
2 / 5 (3) Aug 24, 2011
IMHO, Dark Energy and Dark Matter are just fancy names for variables instead of the usual "x" and "y" any algebra student remembers. They allow for equations to be solved without actually knowing what the variable is, but it can be substituted whenever it's actually found.
HannesAlfven
1.5 / 5 (6) Aug 27, 2011
Body-temperature brown-dwarf stars play a very central role in David Talbott's Saturnian reconstruction. The diffusely illuminated atmospheres of these bodies can apparently expand to great distances, far beyond the orbits of planets. This is a very important fact, as that would suggest that those planets have neither seasons nor days -- the perfect location for the origin of life.

These things are mentioned in Wal Thornhill's book, "The Electric Universe".
ROBTHEGOB
1 / 5 (4) Aug 28, 2011
Weren't there some "y" dwarfs in the Clinton administration? Or maybe it was the Carter administration.
Shootist
1.2 / 5 (5) Aug 28, 2011
Weren't there some "y" dwarfs in the Clinton administration? Or maybe it was the Carter administration.


There is a debauched dwarf in Game of Thrones.

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