NASA: WISE Mission Discovers Coolest Class of Stars

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NASA: WISE Mission Discovers Coolest Class of Stars

Post by bystander » Wed Aug 24, 2011 5:02 am

NASA's WISE Mission Discovers Coolest Class of Stars
NASA JPL-Caltech | WISE | 2011 Aug 23
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 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."

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 telescope performed the most advanced survey of the sky at infrared wavelengths 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.

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.

The Discovery of Y Dwarfs Using Data from the Wide-field Infrared Survey Explorer (WISE) - MC Cushing et al The First Hundred Brown Dwarfs Discovered by the Wide-field Infrared Survey Explorer (WISE) - JD Kirkpatrick et al
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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by StarCuriousAero » Thu Aug 25, 2011 1:40 am

What exactly distinguishes a small brown dwarf like this from a planet like Jupiter? Also, has it been ruled out that stars like this aren't at least partially contributing to the elusive dark matter problem? I would very much enjoy a discussion on this topic... :-D

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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by bystander » Thu Aug 25, 2011 2:24 am

StarCuriousAero wrote:What exactly distinguishes a small brown dwarf like this from a planet like Jupiter? Also, has it been ruled out that stars like this aren't at least partially contributing to the elusive dark matter problem? I would very much enjoy a discussion on this topic... :-D
Mass, if over 10 Jupiter masses. it is unlikely to be a planet. Currently, anything over 13 Jupiter masses is considered a star.

Distinguishing low-mass brown dwarfs from high-mass planets
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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by neufer » Thu Aug 25, 2011 2:25 am

StarCuriousAero wrote:
What exactly distinguishes a small brown dwarf like this from a planet like Jupiter?
A lone object in space that is at room temperature (~ 300K) or more is assumed to be a star heated by internal fusion.
http://en.wikipedia.org/wiki/Brown_dwarf wrote:

<<Ways to distinguish brown dwarfs from planets:
  • 1) Mass, if over 10 Jupiter masses, means a body is unlikely to be a planet.

    2) X-ray and infrared spectra are telltale signs. Some brown dwarfs emit X-rays; and all "warm" dwarfs continue to glow tellingly in the red and infrared spectra until they cool to planetlike temperatures.
Brown dwarfs are sub-stellar objects which are too low in mass to sustain hydrogen-1 fusion reactions in their cores, which is characteristic of stars on the main sequence. Brown dwarfs have fully convective surfaces and interiors, with no chemical differentiation by depth. Brown dwarfs occupy the mass range between that of large gas giant planets and the lowest-mass stars; this upper limit is between 75 and 80 Jupiter masses (MJ). Currently there is some debate as to what criterion to use to define the separation between a brown dwarf and a giant planet at very low brown dwarf masses (~13 MJ ), and whether brown dwarfs are required to have experienced fusion at some point in their history. In any event, brown dwarfs heavier than 13 MJ do fuse deuterium and those above ~65 MJ also fuse lithium.>>
StarCuriousAero wrote:
Also, has it been ruled out that stars like this aren't at least partially contributing to the elusive dark matter problem? I would very much enjoy a discussion on this topic... :-D
There would have to be many thousands of these observed within 40 light years of the earth if they are going to play an important role in the dark matter problem.
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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by Ann » Thu Aug 25, 2011 2:46 am

bystander wrote:
StarCuriousAero wrote:What exactly distinguishes a small brown dwarf like this from a planet like Jupiter? Also, has it been ruled out that stars like this aren't at least partially contributing to the elusive dark matter problem? I would very much enjoy a discussion on this topic... :-D
Mass, if over 10 Jupiter masses. it is unlikely to be a planet. Currently, anything over 13 Jupiter masses is considered a star.

Distinguishing low-mass brown dwarfs from high-mass planets
Personally I'm curious about the excitement. It seems pretty obvious to me that astronomers are hunting for objects that are at the dividing line between planets and stars. But so what? I can imagine the announcements:

"Today astronomers have found an object which is believed to contain only 13.5 Jupiter masses.

Today astronomers have found an object believed to contain only 13.4 Jupiter masses.

Today astronomers have found an object containing only 13.3 Jupiter masses.

Today astronomers have found an object containing only 13.2 Jupiter masses.

Today astronomers have found..."


Image

I was looking for an image of a really bored yawn, but this kitty was prettier.













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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by Beyond » Thu Aug 25, 2011 3:16 am

Awww... what a purrfect widdle puddy tat. :D Ann, you were WISE to post that coolest cat-star picture :D 8-) :D
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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by neufer » Thu Aug 25, 2011 3:53 am

Ann wrote:
I was looking for an image of a really bored yawn, but this kitty was prettier.
[list][list]King Henry IV, part II Act II, scene I[/list]
FALSTAFF: I'll tickle your catastrophe.[/list]
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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by Ann » Thu Aug 25, 2011 9:21 am

Beyond wrote:Awww... what a purrfect widdle puddy tat. :D Ann, you were WISE to post that coolest cat-star picture :D 8-) :D
Thanks!! :D Glad you like it!

But Art, what do you mean that my cat (which isn't my cat) is a cat-astrophe? :evil:

(Although it would be tempting to tickle it a little.

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Re: NASA: WISE Mission Discovers Coolest Class of Stars

Post by neufer » Thu Aug 25, 2011 11:30 am

Ann wrote:
Art, what do you mean that my cat (which isn't my cat) is a cat-astrophe? :evil:

(Although it would be tempting to tickle it a little.)
It's the only way to get it out from under that snake:
http://en.wikipedia.org/wiki/Earthquake wrote:
<<In Norse mythology, earthquakes were explained as the violent struggling of the god Loki. When Loki, god of mischief and strife, murdered Baldr, god of beauty and light, he was punished by being bound in a cave with a poisonous serpent placed above his head dripping venom. Loki's wife Sigyn stood by him with a bowl to catch the poison, but whenever she had to empty the bowl the poison dripped on Loki's face, forcing him to jerk his head away and thrash against his bonds, which caused the earth to tremble.>>
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