Shine on you crazy diamond: Distant dwarf may hide space jewel Astronomers say they have discovered a white dwarf star that could be the coldest of its type ever detected. The boffins said that the dwarf star resides alongside the pulsar PSR J2222-0137 and could hold at its core a diamond the size of the earth. Estimates would place the star's age at 11 billion years, roughly the same as …
Take a FAIL point, dude. The "new kind of physics" you are seeking hides behind the terms "compact star", "electron degeneracy pressure" and more generally "degenerate matter". You should also take a tour around "Pauli exclusion principle" for a minor diversion and a bit of background.
And yes, the "diamond" is very dense. A white dwarf will have a mass of anywhere from 0.2 to 1.44 times the mass of the Sun, but packed into an object about the size of the Earth.
For more detail than you probably ever wanted to know, check out http://en.wikipedia.org/wiki/White_dwarf .
And join the "5000 times cooler" sinner in the corner. There's plenty of spare dunce hats.
Take a FAIL point, dude. The "new kind of physics" you are seeking hides behind the terms "compact star", "electron degeneracy pressure" and more generally "degenerate matter". You should also take a tour around "Pauli exclusion principle" for a minor diversion and a bit of background.
Take a fail point yourself. Electron degenerate matter is unable to form any kind of chemical bond (because of the lack of electrons) and therefore unable to crystalise.
"Take a fail point yourself. Electron degenerate matter is unable to form any kind of chemical bond (because of the lack of electrons) and therefore unable to crystalise."
Did I mention chemical bonds or crystals? No. I referred to it as a "diamond" (in quotes), meaning a so-called diamond, because various people had called it a diamond, not because I thought it would be even slightly reasonable to call it such a thing.
Did I mention chemical bonds or crystals? No. I referred to it as a "diamond" (in quotes), meaning a so-called diamond, because various people had called it a diamond, not because I thought it would be even slightly reasonable to call it such a thing.
Exactly. This is an article relating to crystalline carbon and you claim it to be degenerate matter. It isn't and it can't be.
As we all know normal matter is mostly empty space between the nucleus of an atom and its electron shell(s) and the also between the shells.
The so called diamond at the heart of this white dwarf would be extremely dense as a white dwarf is made of electron degenerate matter (collapsed matter) and while the carbon nuclei may be intact (so it is still the element carbon by proton and neutron count) the electron shells are compressed and changed so the nuclei can sit much closer to each other, not held really far apart by normal interacting electron shells. As the article states just over one solar mass in a spheroid the size of the earth. Density is around 1,000Kg per cubic centimetre. Bit heavy for even the average engagement ring!
Doubtful that the carbon nuclei are in tetrahedral diamond configuration as all molecular/crystalline formation are governed by electron shell interactions.
@ Grikath
This is just regular old physics. This diamonds are heavier than the diamonds you find on Earth, since in each one of them have more carbon molecules than in diamonds found on Earth due the gravity and compression that they did undergo when they where formed in a core of a supernova. That density is not changed even if a peace of them would be removed from the surface of a white dwarf (I don't see how that would be possible, this white dwarf has the same gravity as our own sun).
It is also worth noticing that this white dwarf is orbiting a neutron star, even heavier and more dense star then the white dwarf.
You can read an science paper on this subject here.
http://cds.cern.ch/record/435428/files/0004317.pdf
"That density is not changed even if a peace of them would be removed from the surface..."
I think you'll find the density would indeed change quite a bit if you managed to remove the pressure causing the degeneracy as the matter reorganises itself as (possibly) a more or less regular diamond.
@ Anonymous Coward
"I think you'll find the density would indeed change quite a bit if you managed to [...]". Now you have to explain this claim to me. With data, please.
I did not find not the explanation I was looking for, but this is close enough. Teaspoon of white dwarf stuff has the weight of around 5 tons.
http://www.popsci.com/technology/article/2009-10/what-would-happen-if-i-ate-teaspoonful-white-dwarf-star
Didn't Arthur C Clarke write about something like this? It might have been speculation about what was under all the clouds of Jupiter, I don't recall exactly. But basically, same sorta physics: lots of matter under intense pressure at the center of a cloud of hot gas tends to end up in the strongest, simplest atomic structures, i.e. a tetrahedron of carbon atoms, in other words, a diamond.
Hoping some reg reader will know what I'm referring to.
Actually, brown dwarfs are much cooler. :p
As shown in your own article here, brown dwarf stars can be _much_ colder:
http://www.theregister.co.uk/2011/08/24/y_dwarfs/
So, it's very cool that this one is the coldest white dwarf found - and a diamond inside to boot! - but it isn't quite "the coldest stellar object ever detected"..
... WTF "5000 times cooler" is supposed to mean.
If it is supposed to mean "surface at 1/5000th the absolute temperature" (the only thing we can actually measure about either its temperature or the Sun's), then it has a surface temperature of 1.1 Kelvin, which is, indeed, pretty cold, but seeing it at that temperature is basically impossible, and anyway the surface is described as being at 3000 K.
If, on the other hand, we follow the 3000 K surface temperature, then the 5000 times cooler idea leads me to accuse the Sun's surface temperature of being around 15 megaKelvin, which is grossly over the mark (around 5800 K). 15 megaKelvin is reasonable for the Sun's core, but that's actually just speculation, and "5000 times cooler" comparing the surface of the white dwarf to the core of the Sun is a highly questionable comparison. (I would normally be a lot more blunt about this analysis, but I'm in a charitable sort of mood today.)
Overall, then, whoever said this is guilty of sins against language and should go sit in the corner with a dunce hat on. For shame!
I was thinking this too, I guess they must be comparing the white dwarf's surface temperature to the temperature of the Sun's core, but that's kind of reasonable: a white dwarf IS essentially the core of a Sun-like star, after it's turned into a red giant and gradually lost its atmosphere, so the very youngest and therefore hottest white dwarfs would presumably have a temperature in the order of megaKelvins.
Also, 15 million K for the Sun's core is not exactly speculation, we have very good reasons to know it's roughly that value: amongst other things, the nature of the neutrinos that we detect coming from the Sun's core tell us a lot about its temperature. (In fact, a while back, scientists were confused because the neutrinos seemed to tell us that the core was cooler at around 10 million K, and yet we knew for other reasons it should be higher, but this mystery was solved when we discovered that neutrinos can "oscillate" by changing their "flavour" as they travel to Earth.)
I tripped over that phrase as well. Somebody either has trouble working the calculator, or has trouble writing proper references. If it's the core that is 3000k, then don't mention the surface in the same sentence.
Aside from that, although I love reading about space and everything in it, I am left unimpressed by such comparisons. A dwarf star has an Earth-sized diamond at its core, so what ? It's not like we'll ever have the technology to go mine it, what with the gravitational pull and density and all (and that is supposing that we have the means to get there within a human lifetime).
No, the only important thing about this discovery is that we are capable of detecting fainter and fainter objects, and that is a Good Thing (TM). That is the point of the discovery, not the fact that there may be a planet-sized diamond at its core.
They should have said it was 5 KiloFonzies cooler.
Given that the temperature of the Sun is about 548 H* and PSR J2222-0137 is a purported 298 H, clearly the correct route would be to state that it is thought to be around 250 H less hot than the day star.
* Hiltons, a proper El Reg unit of measure
... leads me to accuse the Sun's surface temperature of being around 15 megaKelvin, which is grossly over the mark (around 5800 K). 15 megaKelvin is reasonable for the Sun's core, but that's actually just speculation...
The hottest part of the sun is actually the core, at (you guessed it) around 15 million Kelvin, the temperature needed to sustain nuclear fusion. The coronasphere, the plasma layer above the visible 'surface', is also at a few million Kelvin. The surface that we see is actually the coolest bit.
edit - since a white dwarf no longer sustains nuclear fusion, the core temperature is likely to be similar to the surface temperature - if it is indeed made of diamond, then it's going to be a very good thermal conductor.
Given the density of the remnant it should be even better than any terrestrial matter in the thermal conduction stakes and probably near super conductive given the free state of so many electrons. Since these type of remnants tend to be a mix of carbon and oxygen as the end fusion products can't see it being a diamond by any realistic description.
I think you will find that the core temperature of a white dwarf is anything but equal to the surface temperature. I have not done the math on this, and I have only backed up my initial thoughts on the matter to the wikipedia article on white dwarfs, but it is quite simple.
1. If they are isothermic or close to it and you a have surface that is a few thousand Kelvin the radiation will be quite high as that is not far from an active star. Of course in total quite a lot less since the surface area is a lot smaller. But the heat capacity simply isn't big enough to keep this running for billions of years with a core temperature that is the same, even with it's big mass.
2. If the core at an active star is several million degrees and the surface only a few thousand, why would that change when it collapses after fusion stops?
Anyhow, white dwarf interior physics is not my specialty, but I find this bit from the wiki article not to contradict my limited understanding:
Although thin, these outer layers determine the thermal evolution of the white dwarf. The degenerate electrons in the bulk of a white dwarf conduct heat well. Most of a white dwarf's mass is therefore almost isothermal, and it is also hot: a white dwarf with surface temperature between 8,000 K and 16,000 K will have a core temperature between approximately 5,000,000 K and 20,000,000 K. The white dwarf is kept from cooling very quickly only by its outer layers' opacity to radiation.
So you are right it being isothermic, just that is has an atmosphere/surface that is not.
Its cold outside, there's no kind of atmosphere,
I'm all alone, more or less.
Let me fly, far away from here,
Fun, fun, fun, In the sun, sun, sun
*As for the original question what does 5000 times cooler mean, the closest I got was in total radiation. If you ignore the to the power of four bit in black body radiation you get that it's surface is about one ten thousandth and the temperature is about half.
Yes, I got caught up by that too and just simply assumed that it was either an error or a poor wording.
In the second case my wrong guess was that the comparison was referred to the bolometric luminosities somehow that would account for the radii difference (or the square of the ratio to be more precise) ... never did I take the Sun's core into account (as you suggested), yet it most probably was meant by this article at least. Strange comparison indeed , yet there, it's unequivocal on what is compared though. And the comparison is indeed strange, since according to the wikipedia article, you referred to above, the core of a white dwarf might be 10^3 times hotter than the surface.
This post has been deleted by its author
Let's say we have a temperature of 10,000° (doesn't matter which type of °... real degrees or Fahrenheit). 1 times cooler would be 0°. 2 times cooler would have to then be -10,000°, which would take it to below absolute zero, whichever scale we use. At 5000 times cooler, we definitely have something to write home about.
Now, the comparison had been a matter of how many times warmer, such as our sun being 5000 times warmer than the white dwarf, then that would be a different matter, Instead of multiplying to subtract, we would be multiplying to add. So, if the star was 10,000°, then our sun would be 10,000,000°.
Of course, this just follows the same principles as x% more or x% less.
Or maybe "5000 times as much coolness". Coolness, when referring to temperature and not to jazz, is measured in reciprokelvins, and the thing that is 5000 times cooler has 5000 times as many reciprokelvins, or 1/5000th of the number of kelvins. "It is at one 5000th of the temperature of the Sun" would be a better way of saying it, but this seems to be another instance of a modern trend, that of using these sort of reciprocal units (coolness is the reciprocal of temperature, slowness is the reciprocal of speed, etc) in comparisons, so that "X is N times slower (cooler, smaller, etc) than Y" means that "Y is N times faster (hotter, larger, etc.) than X", or equivalently that "X is 1/N th as fast (hot, large, etc.) as Y". It's stupid, and it lives in the same house as "twice as hot" - this is often used to mean "at 40degC instead of at 20degC".
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