Super cold brown dwarf or is it a planet?

Super cold brown dwarf or is it a planet?
Image of the first ultra-cool brown dwarf (WISEPC J045853.90+643451.9) discovered by NASA's Wide-field Infrared Survey Explorer, or WISE. It is the green dot and is located between 18 and 30 light years away. It is is one of the coolest brown dwarfs known, with a temperature of ~600K. Image: NASA/JPL-Caltech/WISE Team

( -- In a month that has already announced the discovery of a brown dwarf 75 light-years from Earth, NASA’s infrared Spitzer Space Telescope has found what could prove to be an even cooler, and closer, brown dwarf.

In a report released in The , the discovery of WD 0806-661B has been reported. This possible brown dwarf was detected 63 light-years from and has an approximate mass seven times that of Jupiter. The estimated temperature of this possible brown dwarf is 30 degrees Celsius (86F), or equivalent to Earth on a warm summer day. This discovery would make this the coldest brown dwarf discovered.

WD 0806-661B however, is in question of even being a brown dwarf. It has, instead, the potential of actually being a planet, as it is in orbit of a white dwarf, known as WD 0806-661. However, WD 0806-661B has an orbital distance of 2,500 AU, and it is believed that is too distant of an orbit.

This white dwarf star once burned with a mass two times that of our sun. When a star runs out of hydrogen fuel, it becomes what is known as a red giant. After the red giant phase, the star then sheds large quantities of its mass and becomes what is known as a white dwarf. Models predict that when this shedding of mass happens, within its orbit could be pushed into a wider orbit.

It is this possibility of a wider orbit that is in question regarding WD 0806-661B. Could it have once been a large planet orbiting a very large sun, only to be moved when the sun failed? Researchers admit this information will require further measurements.

The idea of finding planets orbiting white dwarfs has also been discussed in a recently published paper by Eric Agol from the University of Washington. Should WD 0806-661B prove to be a planet instead of a brown dwarf, this would further prove Agol's theories.

However, should WD 0806-661B prove to be a brown dwarf, it would be a candidate for a class of brown dwarfs that have only been theorized. Known as the “Y”-class family, this class would include that are cool enough to have water vapor in their atmosphere capable of condensing to form clouds and water.

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More information: DISCOVERY OF A CANDIDATE FOR THE COOLEST KNOWN BROWN DWARF, K. L. Luhman et al. 2011 The Astrophysical Journal Letters, 730 L9 doi: 10.1088/2041-8205/730/1/L9

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Mar 23, 2011
Could somebody do a quick calc and determine the surface gravity? list your assumption for radius. I also wonder how high the clouds would be.

Mar 23, 2011
Could somebody do a quick calc and determine the surface gravity? list your assumption for radius. I also wonder how high the clouds would be.

LOL. Define "Surface". This planet or brown dwarf is presumed to be a gas giant type object. Therefore we have no idea where the surface would begin...and the force of gravity is very dependant on where you stand in relation to it's center.

Mar 24, 2011
For some reason I was thinking that the shed mass would leave a solid core. Wasn't a good morning for me apparently. Guess I didn't think that one all the way through. ;)

I was still thinking pretty hard on the other Agol article and habitable tidally locked planets around white dwarfs and didn't make the transition to star from rocky planet. Something along the lines of, "6 times Jupiter and rocky! Must have killer gravity! Maybe somebody can gin it up while I rot here at work in front of my computer doing accruals."

Mar 24, 2011
I think the gravity on Jupiter is about 250% that of Earth and if this planetoid is six times as massive as Jupiter that would mean it's gravitational pull would be (250 X 6)% that of Earths or 1500% more than Earths. So if you weighed 100 pounds on Earth, you would weigh 1500 pounds on (WISEPC J045853.90+643451.9).

Mar 24, 2011
Maybe by the time we have the technology to travel the distance, we will have the technology to overcome the immense gravitational pull there and establish colonies on its surface.

Mar 24, 2011
Jupiter does have 250% the gravity of earth at an arbitrary point at appx the same pressure as earth. However there would be absolutely no point in trying to colonize the solid (Or liquid hydrogen or helium) surface of that planet or this object. Millions of times of pressure is much harder to overcome than a little extra gravity.

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