Discovery: Record Breaker: Very Cold Brown Dwarf Discovered

[bystander]

Record Breaker: 'Very Cold' Brown Dwarf Discovered
Discovery Space News | Ian O'Neill | 2011 Mar 09

[i]Image Credit: NASA, ESA and G. Bacon (STScI)[/i]

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A brown dwarf, about 75 light-years from Earth, has hit a new low. In fact, its temperature is so low that it is about the same temperature as the cup of tea sitting at my desk. Ladies and gentlemen, meet "CFBDSIR J1458+1013B," the sub-100 degree Celsius (212 F) failed star.*

A group of astronomers headed by Michael Liu, of the University of Hawaii, used the awesome power of adaptive optics on the 10-meter Keck II Telescope on Mauna Kea to probe the very faint infrared signature of this brown dwarf -- which exists as a brown dwarf binary, orbiting with its partner, CFBDSIR J1458+1013A -- revealing that the object may belong to a notoriously rare type of brown dwarf. This object is the faintest brown dwarf spotted by far and it is estimated to be only 6-15 times the mass of Jupiter.

Brown Dwarfs = Stellar Failures?

You may have heard brown dwarfs being referred to as "failed stars" as they are not massive enough to support nuclear fusion in their cores, and yet they can't be called "planets" as they don't exhibit chemical differentiation with depth and have convective flows -- a very star-like quality. Therefore, they exist in a stellar hinterland, where they are neither a star or a planet, and yet exhibit characteristics of both.

But astronomers still classify brown dwarfs by their spectral type (a scale of letters assigned to the luminosity of stars), which relates to their temperature. At the lowest, coolest end of the scale, radiating in infrared wavelengths, are the oddball brown dwarfs.

So far, the coolest brown dwarfs observed exist at the lowest end of the scale, with a spectral class of "T." However, there is a theoretical class "Y" that is even cooler than the T-class brown dwarfs -- they are predicted to have a temperature less than 225 degrees Celsius (440 F).

More Like a Planet? More Like a Star?

Although Y-class candidates have been spotted by other instruments, the Keck telescope has put a very tight constraint on the temperature of CFBDSIR J1458+1013B and it looks as if this brown dwarf has more "planet-like" qualities than "star-like" qualities, with a temperature of 97 degrees Celsius (give or take 40 degrees C).

Could CFBDSIR J1458+1013B be the missing link between stars and planets? How can we work out if this object is more like Jupiter, say, or more like the sun?

Usually, water will exist in a gaseous state in brown dwarf atmospheres. But at such low temperatures, it is expected that water in the brown dwarf's atmosphere will condense to form clouds. Although it is hard to detect condensing water in this brown dwarf's atmosphere, it is certainly a prime "Y" class candidate.

Regardless, CFBDSIR J1458+1013B is the coolest brown dwarf in the cosmic neighborhood and it could help us understand the point at which a star becomes a star and a planet becomes a planet.

*Although brown dwarfs are known as "failed stars," I like to refer to them as "overachieving planets." Whoever said that becoming a star was the pinnacle of stellar living anyway?

Cooler-Than-Steam Brown Dwarf Blurs The Line Between Star & Planet
Discover Blogs | 80beats | 2011 Mar 10

[i]Image Credit: NASA[/i]

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Planetar. Substar. Failed star. Sub-stellar object. Astronomers have pinned each of these monikers on brown dwarfs, a category that has always perplexed scientists because it raises questions about what it means to be a star or a planet. And if that wasn’t enough, now they’ve discovered the coldest brown dwarf yet, blurring the line between planet and star even further.

It’s name is CFBDSIR J1458+1013B, and may be cooler than the boiling point of water (at the pressure of Earth’s atmosphere). This strange body is about 75 light-years from us, where it orbits its binary partner, another brown dwarf. Using the infrared capabilities of the 10-meter Keck II Telescope on Mauna Kea, University of Hawaii researcher Michael Liu and his team estimated the brown dwarf’s temperature, and have a ballpark range for its mass: between 6 and 15 times the mass of Jupiter.

It’s special because it may be a class Y dwarf (temperature less than 225 degrees Celsius (440 F)), a type of object whose existence astronomers had predicted but never actually found. Before this candidate arose, the coolest known brown dwarf was in the T spectral class; while there have been a few Y-class candidates in the past, scientists have a better grasp on the temperature of this one: 97 degrees Celsius, plus or minus 40C.

Another cool (ahem) thing about this particular brown dwarf is its mass. An object less than 13 Jupiter masses is too light to fuse atoms of deuterium, a heavy isotope of hydrogen; objects above 13 Jupiter masses can fuse deuterium. The uncertainty over CFBDSIR’s mass—estimated as between 6 and 15 Jupiter masses—could put it on either side of the line. And to top it off, it may be so cool that its gases could form clouds, a very planet-like thing to do.

So much still remains to be known about this particular brown dwarf and brown dwarfs in general, but one thing is set, at least for now: It’s the coolest one we’ve ever seen, and it may help us sort out this vague and messy mystery about the smudgy line between stars and planets.

CFBDSIR J1458+1013B: A Very Cold (>T10) Brown Dwarf in a Binary System - MC Liu et al

• arXiv.org > astro-ph > arXiv:1103.0014 > 28 Feb 2011 (v1), 07 Mar 2011 (v2)

[bystander]

Ultra-Cold Brown Dwarf Discovered?
Discovery Space News | Ian O'Neill | 2011 Mar 12

Image Credit: NASA

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Not to be outdone by the Keck II telescope in Hawaii, NASA's infrared Spitzer Space Telescope may have discovered a brown dwarf even cooler than the brown dwarf Discovery News reported on last week.

Keck spotted "CFBDSIR J1458+1013B," a brown dwarf 75 light-years from Earth with a mass of 6-15 times that of Jupiter, and from observations realized that this very dim object must have a temperature of less than 100 degrees Celsius (212 F) -- about as hot as boiling water.

This discovery has very important ramifications for star and planetary physics, because a brown dwarf is neither a star or a planet, it is an object that bridges the gap between planets and stars. For this reason, and because brown dwarfs do not possess enough mass to sustain nuclear fusion in their cores, that they are often dubbed "failed stars."

So, the potential Spitzer discovery of an "ultra-cold" brown dwarf has excited scientists even more. Spitzer's candidate brown dwarf, detected 63 light-years from Earth with a mass of approximately seven times the mass of Jupiter, appears to have a temperature of 30 degrees Celsius (86 F)! This "room temperature" brown dwarf is called "WD 0806-661B."

Interestingly, WD 0806-661B orbits a white dwarf star (called, unsurprisingly, WD 0806-661) and could be considered an exoplanet. But it orbits at a huge distance: 2,500 AU -- or 2,500 times the distance between the sun and Earth. For it to be a planet, it would need to be orbiting far, far closer to the white dwarf.

However, there is another possibility. This white dwarf star was once a star two-times the mass of our sun. White dwarfs are what remains of an old star after it has run out of fuel and died.

Indeed, our sun has a similar fate in approximately 4 billion years time. After it has run out of hydrogen fuel, puffed up as an angry "red giant" and swallowed the Earth as it expands, our red giant sun will eject its outer layers, leaving a white dwarf shining in the core of the resulting "planetary nebula." ...

Models predict that once the sun has shed huge quantities of mass after its red giant phase, the remaining planets of the solar systems will drift into wider orbits. Is this what happened to WD 0806-661B? Was it once a very massive planet orbiting a star twice the mass of the sun? Further measurements of the object are obviously needed.

The discoveries of CFBDSIR J1458+1013B and WD 0806-661B (if it is indeed a brown dwarf) are unprecedented; they could represent a population of low-temperature brown dwarfs that have more "planet-like" than "star-like" characteristics.

They are so cool in fact that water vapor in their atmospheres could condense to form clouds of water droplets. Brown dwarfs that are capable of this belong to a specific "Y"-class family of these objects. Y-class brown dwarfs have only been theorized, but these two new discoveries are prime Y-class candidates.

Newly found brown dwarf is ultra-cool
New Scientist | Cosmology | 2011 Mar 12

WE THINK of stars, even the failed ones called brown dwarfs, as being lethally hot. That picture has been confounded by a newly discovered brown dwarf - at room temperature.

Like fully fledged stars, brown dwarfs form from collapsing gas clouds, but they are not massive enough to sustain nuclear reactions. Instead, they briefly shine red from the heat of formation, then fade. Still, the coolest known brown dwarfs are all hot enough to roast any spacefarers who venture too close.

Now Kevin Luhman of Pennsylvania State University in University Park and colleagues have used NASA's infrared Spitzer Space Telescope to detect the glow of what appears to be a brown dwarf at just 30 °C (Astrophysical Journal Letters, DOI: 10.1088/2041-8205/730/1/L9).

The object, which orbits a white dwarf star 63 light years from Earth, weighs seven times as much as Jupiter. At that mass, it would normally be considered a planet. But planets form from discs of gas and dust around stars, and the researchers say that the object, known as WD 0806-661 B, lies too far from its star - at 2500 times the Earth's distance from the sun - to be deemed a planet if it formed where it is.

The object is a lot hotter than Jupiter, which is at a frigid -149 °C, and much cooler than the next coolest brown dwarf, at 100 °C. This means that WD 0806-661 B will act as a "missing link" to reveal how temperature affects the atmosphere and spectral features of objects that are roughly the size of Jupiter.

Discovery of a Candidate for the Coolest Known Brown Dwarf - KL Luhman et al

• Astrophysical Journal Letters 730(1) L9 (2011 Mar 20) DOI: 10.1088/2041-8205/730/1/L9
  arXiv.org > astro-ph > arXiv:1102.5411 > 26 Feb 2011

[Beyond]

pun intended

[Ayiomamitis]

Dear group,

I have not been able to locate the RA/Dec for this binary system. Does anyone have a lead in this regard?

Thanks.

Anthony.

[bystander]

Hope this helps:

CFBDSIR J1458+1013:

• http://www.solstation.com/stars3/cfbdsir2.htm
  http://exoplanet.eu/star.php?st=CFBDS+1458

WD 0806-661:

• http://solstation.com/stars2/wd0806-6.htm
  http://exoplanet.eu/star.php?st=WD+0806-661

[Ayiomamitis]

Thank you, thank you, thank you!!!!

Anthony.

[neufer]

Very Cold Brown Dwarf Discovered

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[BMAONE23]

That looks more like a Cold White Dwarf

maybe he is just in Gnome

[Beyond]

Neufer - You're priceless