Question about supernova

[aplefka]

Okay, so I read that a supernova can reach up to 1 billion degrees celsius, which made me wonder, is there a known radius around such temperatures that if you go into that area you're basically toast. I mean if the sun is only 15 million degrees celsius at the core and 6,000 degrees celsius on the outtermost part and it's still over 37 degrees celsius here, isn't it safe to say that even around the sun there's a certain point where matter just melts or disintegrates? Is there any way to measure this without using trial and error?

 

[unipidity]

Im not entirely sure what you are asking. Different things are going to change phase at different temperatures, for sure. And nuclear processes can get more common with higher temp. The matter itself isnt going to go anywhere though- disintegration into individual molecules, atoms, particles, yes, but you cannot disassociate quarks from each other due to their large binding energy. And electron etc are fundamental, and cannot disintegrate. So.. erm.. .rephrase the question, please.

 

[Bona Fide]

^Exactly. For example, water evaporates at 100C, but iron doesn't. It depends on the material. Seeing as humans are 75% water...I think 120C should be enough to fry us.

 

[aplefka]

Yeah I suppose I worded it a bit badly. Of all known substances, what's the one with the highest boiling or melting point and how close could it get to a supernova explosion? Obviously that'd be the point in which nothing could get any closer if it's the element/compound with the highest boiling or melting point, which is kind of what my question was.

 

[cquark]

Originally posted by: aplefka
Yeah I suppose I worded it a bit badly. Of all known substances, what's the one with the highest boiling or melting point and how close could it get to a supernova explosion? Obviously that'd be the point in which nothing could get any closer if it's the element/compound with the highest boiling or melting point, which is kind of what my question was.

The Sun's core is hot enough to turn any element into a plasma.

The core of a heavy star that becomes a supernova is made of nuclear matter, considerably denser and more difficult to destroy than any matter that can be on Earth, and it's essentially a fluid while the star is active.

 

[alpha88]

Just a quick comment:

Temperature isn't a 'real' quantity, but rather a statistical measurement.


Simply put, temp is just the average energy or motion of the particles. When particles have more than a specific amount of energy, they can no longer hold certain bonds.

Example:

Beyond 100 c, the average water molecule has too much energy to stay connected with neighbooring water molecules (so it becomes a vapor instead of a liquid).

Likewise at higher energies (corresponding to the temp of the sun), electrons have too much energy to stay bonded to a specific atom, so the nuclei and electrons all fly around in what we call a plasma.

I've got no idea how much energy is required to prevent the strong force from holding stable nuclei together, but I'm sure there is a point where that happens.


Regarding radius from a region of high temp - it doesn't matter what the temp is nearby, only right at your location (well, until that nearby temp heats up your area). Think of a thermos - you can hold them just fine, your hand just an inch from boiling hot water, with no problem. Of course, there aren't any materials that could insulate from super nova temps, since they would quickly be broken down into plasma.

 

[JustAnAverageGuy]

Let me reword the question for him.

How close to a supernova could you be and still be safe?

 

[BespinReactorShaft]

Let me hazard a guess. I think the basic query is: In space/vacuum, how far does a heat source of a particular temperature radiate considering how much the temperature reduces per unit distance?

 

[wetcoastguy]

When a supernova goes "bang" your problem isn't heat energy, it is matter. The "safe" distance will be measured in light years.
By the time you have seen the "bang" you be just about to be creamed by very high energy particles. Heat is the least of your worries.

 

[unipidity]

Well, in a perfect vacuum with isotropic radiation, its just an inverse square. The only thing that could possibly survive the centre of a supernova is... a big lump of neutronium. AKA a neutron star.

Weird question. The majority of the energy is given off in the form of neutinos, I believe, so its not as dangerous as it could be. That is, assuming that they interact rarely enough (with anything else) that even the vast flux (number coming through your body) doesnt matter. I really dont know.

 

[TuxDave]

Originally posted by: BespinReactorShaft
Let me hazard a guess. I think the basic query is: In space/vacuum, how far does a heat source of a particular temperature radiate considering how much the temperature reduces per unit distance?

Assuming a vacuum, wouldn't it be inversely proportional to distance cubed?

 

[f95toli]

No. the inverse squared.
Just like the light from a light bulb.

Assuming the radiation from a source Q is isotropic the energy/area at a distance R
is Q/(4*pi*R^2),

(4*pi*r^2 is the surface area of a sphere)

 

[aplefka]

Okay guys, thanks. I think I made the question a lot harder than it needed to be and JAAG was right.

The reason I said a supernova was because that's the hottest thing I know of and I wondered how far the heat would emit in a sense.

 

[imported_BigT383]

Actually in a vacuum there would be only two ways for the heat of the supernova to reach you- when you're hit by the hot matter from the explosion itself, or the radiation (light) from the supernova. Based on your question you're not worried about what happens after the matter from the explosion hits you, which is good both because I don't know and because you're probably screwed at that point anyway.

Before the physical matter from the explosion of the star hit you, all you have to worry about is the radiation. The change in your temperature would depend on several things:
1. How much radiation you recieve (how big of a profile you present to the star, how close you are to the star)
2. Your reflectivity - if you're pitch black you'll absorb a lot more radiation than if you were a mirror.
3. How much radiation you can re-radiate. (Basically, how much of a heatsink are you?) This would have to do on not only your thermal conductivity (how fast the heat could move through you; which for humans is probably similar to water) and how much surface area you have that is absorbing radiation compared to your surface area that isn't, which points back to number one, and also in how much time you absorb the radiation. In a supernova, you'd be getting a lot of radiation really fast.
4. How big you are. If a planet and a brick absorb the same amount of radiation, the brick's temperature will go up a lot more than the planet's because there isn't as much matter for the energy to be distributed through.

Did I miss anything?

 

[silverpig]

Originally posted by: aplefka
Okay guys, thanks. I think I made the question a lot harder than it needed to be and JAAG was right.

The reason I said a supernova was because that's the hottest thing I know of and I wondered how far the heat would emit in a sense.

It doesn't matter how hot, it matters how much. You can take a small electric arc at 10k degrees and be fine, but a forest fire at 1500 degrees will nuke you to a crisp.

And the hottest place in the current universe is right here on earth. The energy of particles in particle accelerators is characteristic of big bang era physics where the temperatures were hundreds of billions of degrees.

 

[unipidity]

Under what circumstances is it anything other than radiation and matter that tranmits energy?

With something like a supernova, it depends on the total flux through your body. The bigger you are, the better (asuming you are also made of a perfect conductor) since vol obviously scales better than X-section. Having said that, if absorption is a 3d thing (which it is at stupidly high intensities, like close to a nova), that will be an issue.

Does anyone feel like doing a calculation? Would the remnant + ISM at, say, a light year away from an 8 Solar mass supernova and going at c/10 cause any 'damage' to the earth? That is, assuming it hasnt been fried by the radiation by magic.

 

[Jeff7]

I believe quasars are more powerful yet than a supernova - but that's a different scale. Quasars are thought to be the centers of galaxies with supermassive black holes. They output incredible amounts of energy as the matter falls into the black hole. So you'd be looking at a number of whole stars getting turned into energy wholesale. All we need is a good blast of gamma radiation from one of them nearby and we'd all be dead before we knew what hit us.

 

[f95toli]

Originally posted by: unipidity
Under what circumstances is it anything other than radiation and matter that tranmits energy?

Conduction through solid matter via phonons and/or free electrons.

 

[imported_BigT383]

Well heat is transmitted directly through matter because if the matter is dense enough and has "thermal conductivity" then the fast moving molecules will hit the slow moving molecules (or affect them through electromagnetic interaction), causing the slow ones to speed up and the fast ones to slow down- thus the heat (which is just a measurement of the speed of the component molecules) gets distributed throughout the mass. If you're talking about photons, you're talking about radiation. In any case, unipidity is right. ;-)

 

[f95toli]

No, no phoTons.
PhoNons (with an N instead of the T)
Phonons are basically quantized lattice vibrations.

What you are describing is basically convection in a gas, in solids heat is transmitted via conduction wihout any net displacement of matter, the ions vibrate around their average position in the lattice and since they are all interacting the resulting waves can spread thorughout the system.

If you treat the system quantum mechanically you end up with a number of modes which correspond to different phonons, there are both longitudinal and transversal phonons with slightly different properties.

In metals you also have conduction of heat via free electrons but that is only important at low temperatures.

 

[unipidity]

Phonons are hardly entirely divorced from matter, are they? They remain a property of the matter, despite being quasiparticles, and it is the matter than tranmits the energy.

 

[Mday]

space is a vacuum. heat does not conduct across a vacuum. now, if you were anywhere close to the gasses for heat to conduct, you'd be toast anyway. now, the light you would absorb if you were within such a radius is essentially going to give you a nice tan. All the other radiation given off would essentiall kill you. of course, gasses are always expelled, so basically, if that crap touches you, you're dead. The impact will pretty much knock you off your position and quickly incinerate you. You wont be toast, you'd be ash.

it's hard to say without being more specific since your question is a little vague.

 

[BespinReactorShaft]

Originally posted by: Mday
space is a vacuum. heat does not conduct across a vacuum.

Hmm, doesn't heat propagate via three methods -- conduction (e.g. solids), convection (e.g. gases) and radiation (e.g. vacuum)?

 

[Calin]

Originally posted by: TuxDave

Originally posted by: BespinReactorShaft
Let me hazard a guess. I think the basic query is: In space/vacuum, how far does a heat source of a particular temperature radiate considering how much the temperature reduces per unit distance?

Assuming a vacuum, wouldn't it be inversely proportional to distance cubed?

It's the distance squared. Just remember that the effect of an instant explosion is only on the surface of a sphere, not on all its volume

 

[f95toli]

Originally posted by: unipidity
Phonons are hardly entirely divorced from matter, are they? They remain a property of the matter, despite being quasiparticles, and it is the matter than tranmits the energy.

Well, I guess it depends on how you look at it. My main point was that there are 3 ways to transfer heat: Conduction, radiation and transport via particles that are actually moving (e.g. convection) and carry kinetic energy that can be transfered to/from any surface where they are absorbed or adsorbed.

Anyway, I would argue that in most physical models it is best to think of phonons as NOT being simply a "property" of matter, on one hand the phonon-spectrum is of course determined by the medium but phonons are as you say quasiparticles and in most cases (e.g. electron-phonon or phonon-phonon scattering) it is best to think of them as "real" particles.