Coldest Place in the Universe

Chris Gondek writes "The Sydney Morning Herald has an article on how NASA has released a high-quality image of the coldest place found in the universe. Five thousand light years from Earth in the constellation of Centaurus, the nebula, a gas cloud formed from a dying star, has a temperature of minus 272 degrees. It is only one degree warmer than absolute zero, the coldest possible temperature, when atoms cease to vibrate and radiate no heat whatsoever. This radiation is the remnant of the Big Bang, the explosion which forged the universe in trillion-degree temperatures. More than 11 billion years later, this heat has cooled to minus 270 degrees, but is still detectable."

Comments

Grumble, grumble - absolute zero

[altairmaine]

As it turns out, absolute zero is not the "coldest possible temperature". It is impossible to attain absolute zero, as a little basic quantum mechanics tells us. Particles will ALWAYS retain some amount of energy, the "Zero Point Energy", which cannot be removed. More accurately, we can say that absolute zero is the lower bound on the range of possible temperatures - but is not included.

Re:Grumble, grumble - absolute zero

[JohnFluxx]

I just thought... one way to perhaps show that you can't reach zero is that to cool something you either need:

*) Something colder, to cool it - but you can't get colder than 0.

*) A bigger space to put the nonzero heat it - but trivally if you expand something with non-zero temperature into an finite space, then the result is still going to be above zero.

*) If it radiates/conducts/etc heat away, then it must be into an area that has a non-zero heat, so that will (instinctively) also radiate an equal or greater amount of heat back again. Hmm, thinking about it this means you can't have a one-way heat shield, or something that absorbes without emitting. (Unless a material stops radiating/conducting below a certain temperature.)

There's probably some other cases I missed - I don't know anything about this field. :) Is there any other way to cool something other than these cases?

Re:Grumble, grumble - absolute zero

[Tim C]

Energy is not quantised. The energy states of a bound particle, eg an electron orbiting a nucleus, are quantised.

The energy of a free particle is not, and can take on pretty-much any value.

Re:Grumble, grumble - absolute zero

[Anonymous Coward]

yes. the zero point energy is correct... but not to be a pest, atoms cannot vibrate as is suggested in the original post. only molecules may vibrate. the zero point energy comes into play for molecules because the energy, E, of a simple harmonic oscillator (simplest approximation) will be:

E = nu ( v + 1/2)

where v is the vibrational quantum number and nu is related to the force contant. nu is positive, and v is always a non-negative integer, so even when v is zero the energy is nu/2. freshman chemistry students are told that this is to accomodate the heisenberg uncertainty principle in that a particle that is not vibrating would have a definite position and momentum.

another poster hinted on what has been stated eloquenty for hundreds of years and restated by homer: in this house, we obey the laws of thermodynamics! the third law states:

"if the entropy of every element in its most stable state at T=0 is taken as zero, then every substance has a positive entropy which at T=0 may become zero, and which does become zero for all perfect crystalline substances, including compounts"

WTF? an alternate statement has more meaning in our context:

"it is impossible to reach T=0 in a finite number of steps".

thus, as altairmaine suggests, it is impossible to reach absolute zero. other posters suggested that it is only possible to cool things by contact with a colder substance. for those people i would suggest doing a google search on the term "adiabatic demagnetization". research into bose-einstein condensates work with clusters of atoms at fractions of a kelvin, and it is not because they have a super-secret stash of a zero-kelvin heat sink. :)

reference: "Physical Chemistry" by Peter Atkins. 5th ed.

Re:Grumble, grumble - absolute zero

[jovlinger]

ah. You have taken the "hell is endothermic" physics test (google that for a laugh: any test whose answers include "take into account the fact that I still have not succeeded in having sexual relations with her" has got to be good).

On a more serious note, look into laser evaporation. It turns out that if you have a laser and an atom, you can tune laser so that only in the presence (sp?) of positive dopler shift (ie, atom moving towards the laser source) will the atom be able to absorb a photon. If you gradually tune the laser to a smaller and smaller band, and you have such a laser pointing from every which way, you have effectively used a laser to cool the atom.

Think of it as shooting ball bearings to stop a bowling ball.

Re:Grumble, grumble - absolute zero

[Anonymous Coward]

In a finite volume energy is quantized, so in your typical experimental setup, energy is quantized.

Re:Big Bang?

[standsolid]

as far as i knew entropy sure did knock that theory out of the water.

http://www.talkorigins.org/faqs/thermo/entropy.h tm l

inform yourself before you post articles as blatantly mis-wroded as this one.

Re:Boomerang?

[Bastian]

It was called the Boomerang nebula because it was first observed with a much lower resolution telescope in which it really did look like a boomerang.

Re:MC Hawking said it best

[Anonymous Coward]

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check it!

TROLL

[Esion Modnar]

Yeah, as if every Sunday school class concludes with "... but this is only our theory of how things happened, don't take this as FACT."

Sometimes its fun to go sacred cow tipping.

Re:cold radiation??

[dpp]

temperature is defined by the movement of atoms, right? how can microwave radiation have temperature?

It's because the cosmic microwave background has the spectrum of a blackbody with the given temperature (2.7K).

Vibration

[4lex]

The lowest level of energy ("fundamental" energy level of a quantum system), which we can equate to absolute zero, because there is no allowed state with less energy *does* have energy, including vibrational energy. Atoms *cannot* "cease" to vibrate, because by doing so they would violate Heisenberg's indetermination principle (they would have an exactly determinate position _and_ moment).

I hope someone corrects me if I am wrong :)

Re:Someone please explain

[dpp]

and what iluminates it? It's bright enough to see with a telescope, but it's -272?

From the article:

"One can say the Boomerang acts as a refrigerator," said astronomer Lars-Ake Nyman, who measured its temperature using the European Southern Observatory radio telescope in Chile. He did this by comparing signals received from carbon monoxide in the nebula with signals from the background radiation.

So it was done with a radio telescope, possibly SEST, by looking at molecular lines from CO. It sounds like they found that the CO was absorbing some of the background radiation. So it wasn't "seen" with a telescope in the way that you're thinking.

Re:Houston we have a problem here

[Xilman]

Conclusion - unless there is some sort of active cooling, nothing can cool down to less than temperature of the background radiation (3K).

Correct.

There is active cooling in this case, and it works the same as a domestic refrigorator. Both systems cool down because gases are expanded, thereby doing work. That energy has to come from somewhere and it comes from the heat content of the gas: it cools in other words.

At the center of nebulae like these is a star which is driving off the remnants of what was previously its outer layers. That is, its atmosphere is expanding. If the heat loss through expansion is greater than the heat input from the rest of the universe, the gas will cool.

Paul

Confusing quote

[Brane]

People who don't read the article (and let's face it, that's most of us, right?), are certain to be confused by the quoted text. The submitter apparently left out this important sentence:

What is interesting for astronomers is that the nebula is colder than the microwave radiation which pervades all of space.

The microwave background radiation is "this radiation" the next sentence refers to.

Re:Query

[Big Mark]

Heat is (mostly) IR radiation. As long as there is space, there will be radiation, so as long as a place exists, it will have heat.

There are other things like thermal neutrons and all that, but we're looking at IR here.

Only not really, IR isn't visible to the human eye...

-Mark

Re:cold radiation??

[Anonymous Coward]

Everything emits radiation due to heat. Think of hot iron, it begins to glow when it is heated high enough. In an ideal case, this is called black body radiation. That means that it emits radiation without regard to its own physical properties.

The equation for this radiation is R = Theta*A*T^4, where theta is 5.7x10^-8 W*m^-2*K^-4, A is the surface area, and T is the temperature, in Kelvins.

Bose Einstein condensates

[dvoosten]

Your average Bose Einstein condensate, made in a lab of your choice, is somewhere between one billionth and one millionth kelvin above absolute zero. So the coldest place in the universe is probably in those labs.

Re:Excuse me, but...

[mjh]

Religion is based on faith, that's what defines it. Once you start having to 'justify' your beliefs, you have lost faith, and most religions (esp. Judeo-Christian ones) would not consider you a member based on your 'lack of faith'. No one gets into heaven (if your religion happens to have one) if they don't have complete faith.

As a Christian, I can agree with you that I can't prove that there's a God. However, I think you might have a misunderstanding of what constitutes "faith". My faith is not based on nothing. I don't believe in God, despite the evidence. I believe in God because I think there's pretty good evidence to support such a belief. For example, I've had experiences that, try as I might, I can't explain without the existence of God. Of course, that's not particularly compelling to you, but just because I can't prove something to you does not make it unreasonable for me to believe it.

For example, my children this morning, woke up at about 6:45am. I let them jump around in their room until about 7:15am, when I finally dragged my tail out of bed and got them, fed them, and sent them off to school. Unfortunately, if I were asked to prove this, I would find it to be very difficult. I suppose that there may be some way to actually prove it, but I know of none, so I'm content in saying that I can NOT prove it to you. That doesn't make me any less certain that it's true. My experiences compell me to believe these things regardless of whether or not I can prove it to someone else.

CS Lewis, in "Mere Christianity", gave a much better description of how faith is not the thing that most people think it is. That faith is not an independant thing from reason and rationality. Here's an excerpt:

I MUST TALK IN THIS CHAPTER about what the Christians call Faith. Roughly speaking, the word Faith seems to be used by Christians in two senses or on two levels, and I will take them in turn. In the first sense it means simply Belief--accepting or regarding as true the doctrines of Christianity. That is fairly simple. But what does puzzle people--at least it used to puzzle me--is the fact that Christians regard faith in this sense as a virtue. I used to ask how on earth it can be a virtue--what is there moral or immoral about believing or not believing a set of statements? Obviously, I used to say, a sane man accepts or rejects any statement, not because he wants or does not want to, but because the evidence seems to him good or bad. If he were mistaken about the goodness or badness of the evidence that would not mean he was a bad man, but only that he was not very clever. And if he thought the evidence bad but tried to force himself to believe in spite of it, that would be merely stupid.

Well, I think I still take that view. But what I did not see then--and a good many people do not see still--was this. I was assuming that if the human mind once accepts a thing as true it will automatically go on regarding it as true, until some real reason for reconsidering it turns up. In fact, I was assuming that the human mind is completely ruled by reason. But that is not so. For example, my reason is perfectly convinced by good evidence that anaesthetics do not smother me and that properly trained surgeons do not start operating until I am unconscious. But that does not alter the fact that when they have me down on the table and clap their horrible mask over my face, a mere childish panic begins inside me. I start thinking I am going to choke, and I am afraid they will start cutting me up before I am properly under. In other words, I lose my faith in anaesthetics. It is not reason that is taking away my faith: on the contrary, my faith is based on reason. It is my imagination and emotions. The battle is between faith and reason on one side and emotion and imagination on the other...

Now just the same thing happens about Christianity. I am not asking anyone to accept Christianity if his best reasoning tells him that the weight of the evidence is against it. That is not the point at which Faith comes in... Faith, in the sense in which I am here using the word, is the art of holding on to things your reason has once accepted, in spite of your changing moods.

The entire chapter expounds on this basic idea. Considering your hobby, I would encourage you to read it. Hope it's helpful.

Image of Nebula

[LeftNose]

For those who are interested, the "high" quality image of the nebula can be found here at the Astronomy Picture of the Day for Tues. 2/20/03.

Click on the image and you'll get the enlarged verson.

Re:Negative temperatures.

[jaoswald]

Sorry, but negative temperatures are ABOVE absolute zero (and above all positive temperatures) in the temperature scale. +infinity and -infinity are the same temperature, but -0 and +0 are not the same temperature.

from cold to hot:

0K...100K..1000K..+infinity/-infinity..-1000K... -1 00K..-0

How can we be sure? A negative temperature system will transfer heat energy to a postive temperature system when the two systems are in thermal contact. Heat flows from hot objects to cold objects, so negative temperatures are hotter.

To summarize the link you provided, negative temperatures only can be realized in systems which have an upper bound to their energy. In practice, this means that one is looking at a restricted set of degrees of freedom of a larger system as a system in isolation from the larger system. For instance, consider just the spins of atoms or nuclei, as separate from the spins+kinetic energy of the atoms or nuclei. As the spins of nuclei are often weakly coupled to the kinetic energy (i.e. collisions or atomic vibrations do not easily flip nuclear spins), this is a good approximation. In reality, if you put the spins into a negative temperature state, the energy of the spins will eventually dissipate, cooling the spins, while slightly increasing the kinetic energy in the system.

(The mathematical reason for this is that temperature is actually the reciprocal of a microscopically meaningful property.)