# Newtons of an exploding Supernova

1. Oct 6, 2011

### Physics quest

Is it possible to calculate the force in Newtons for a Supernova? Have any such calculations ever been possible or done by the scientific community? I can imagine the number would be in the trillions of trillions but I am simply interested.

2. Oct 6, 2011

### Pengwuino

The question is kind of non-nonsensical. A force implies some sort of interaction between two objects. It's like asking what is the force of a gasoline tank exploding. If you built a room around this gasoline tank (and to be more realistic, a tank of hydrogen would be more suited to make a BOOM), you could ask the force the explosion exerts on the walls. However, that's immensely dependent on how close the walls are, what material the walls are made out of, what's the structural support like, etc etc.

Just asking what the force of the exploding tank without it exploding INTO something doesn't really make sense.

Now, I think what you REALLY want to know is the energy of a supernova, which has definitely been figured out to good approximation. And yes, it's a gargantuan amount of energy.

3. Oct 6, 2011

### Physics quest

I think my confusion also comes to the fact that, force exertion being based no surface areas are hard for me to grasp. For example I understand in your case that the exploding gasoline tank exerts its pressure/force on the walls. But then, what in the way explosions work, especially in the case of a s Supernova that is massive ,what if you placed an object in just a part of the supernova, lets say a typical shuttle floating through the system this star is in before it novas, how would you calculate how much force is on this shuttle alone? Even knowing the surface area of a shuttle, the full energy in jouls of a Supernova is spread across its entire body and can apprently eventually cover billions of miles.

Looking it up, a Supernova can be calculated at about 10 to the 44th in joules, so from there assuming you have surface area of a small object like my shuttle example how would you calculate how much force from this? is it possible? Because obviously, this energy expands in every direction.

4. Oct 6, 2011

### Pengwuino

No, just like you can't really calculate how much force an exploding gas can would exert on a room enclosing it. It depends on the material of the wall, the details of the explosion, all sorts of things. In the end, the only real way to find out how much force an exploding gas tank exerts on a wall is to go do an experiment where you blow up a tank of gas.

Determining the forces involved in almost any real world situation is an experimental task or a computationally intensive task, not a theoretical one where you can just say "give me the surface area and energy and I'll give you the force". The only ones I can really think of are rather simple thermodynamic processes (which an explosion absolutely is not) or things involving gravity.

5. Oct 6, 2011

### Physics quest

I see, damn. So I cant really work out the force and energy by itself cannot really give me a gauge of what the Supernova would do to these things I am trying to calculate. I mean we know a Supernova can destroy planetary bodies dont we? so theres no calculation from there I suppose I could use?

I attempted to find how much per surface area a nuclear explosion does in pressure, but all I can find is the full pressure gauge of a nuclear bomb, e.g. something like 60 billion bar. I am trying to do the same with a Super nova to find out percentages of its energy on small objects by comparison to its area of energy but as you say, it probably cant be done.

6. Oct 6, 2011

### Pengwuino

Any supernovae calculations will be done purely through numerical methods. We know a supernova will destroy a planet purely from the fact that it's like asking if a nuclear weapon would destroy a truck placed near it. You don't need to do any calculation; we just know giant explosions + nearby objects = bye bye object.

The real question then becomes how far would a planet have to be in order to not be blown to smithereens. Then you really need to do some computations.

I'm not sure, and don't quote me on this, but I don't think it's even conceptually valid to look at the pressure a nuclear bomb would produce in comparison to a nova. I would imagine the pressure of a nuclear weapon going off would be read as the pressure of the nearby air where it detonates. However, that compression would be the result of the shockwave created by the blast. With a nova, there might be some gas very very near to the star that a shockwave would be formed in, but it will almost immediately get past that and simply expand into space. At that point, it's just tremendous amounts of flying particles and radiation and you run into the same problem of needing to know so much about what happened.

7. Oct 6, 2011

### jetwaterluffy

I thought you could calculate the force of a supernova. You just find the acceleration of the supernova outwards, and multiply it by the supernova's total mass. Obviously the acceleration would change, but from the OP, it looks like he is talking about the maximum force, which I imagine would be based on the acceleration as the supernova first starts exploding, whatever that is.

8. Oct 6, 2011

### Physics quest

Well my final goal is to find out how much force, a small object like a space shuttle or such would take from a vast explosion like a super nova. Lets assume this Shuttle could survive such power/pressure in the first place, I want to calculate how much force divided over its body would impact it.

So finding out total force would be a good start, then to find out how much force would be in say, a 50-100+ square meter area.

Jet is it possible to find out how much an object would take in force form the Supernova? with most of the energy just flying off into space but only a portion(the force hitting the object e.g. shuttle) of it hitting an object, I am tryin to find out how much energy something small like this is having to survive/get hit by compared with the whole super nova.

Another example is if someone, lets say a man was cought in a super nova, he would only be struck by a tiny percentage of its 10 to the 44th power energy, which is obviously more than enough to turn a man to dust but what I am trying to find is how "much" force would be hitting these small objects compared to the energy whole of a nova. Thats why I mentioned my other example of the Nuclear bomb, which can devastate vast areas but its energy covers a large plain, some things whether it be small piecies of metal or scraps survive while large structures fall.

9. Oct 6, 2011

### jetwaterluffy

If you are talking about energy, I think it releases 1044J, but I don't know how much of that is radiation, and it is a different quantity to force. The amount of force an object will take from the supernova depends on, as well as the area, how streamlined it is: something with sails will take a lot more force than a smooth bullet-shaped craft. Also, bear in mind that before it explodes, the star will collapse inward and bounce back out, so you have to decide whether to measure the force from where the surface of the star was, or where it has collapsed into.
PS: Pengwuino probably knows a lot more about this than me, as he has done a master's degree, and I'm still in sixth form.

Last edited: Oct 6, 2011
10. Oct 9, 2011

### twofish-quant

I'm pretty sure you can. You figure out what fraction of the total sphere that the shuttle intercepts, that will give you energy absorbed. Work is the integral of force over distance, so if you can put in some assumptions about how the energy is transferred you can get a force.

11. Oct 9, 2011

### twofish-quant

It's not. If you assume that everything is all radiation, you can calculate the radiation pressure, and then force is pressure * area.

On the other hand, my Ph.D. dissertation was on supernova core collapse. A lot of thinking about the problem is to be able to do some rough calculations so that you know what to point your supercomputer at.

12. Oct 9, 2011

### twofish-quant

This is wrong. There is a lot you can do with algebra or even arithmetic. You try to work through the problem with simple math before you warm up the supercomputer. One reason that you do that is so that you know whether or not you have a bug in your program.

Which you can do with some pretty basic math.

It's actually the same math. Google for Sedov-Taylor blast wave solution.

If you are far enough away from the supernova, then the details of the explosion don't matter. You just assume that 1e+51 ergs of energy got dumped in a point location. At that point there are some basic algebra equations that will get you the pressure evolution away from the supernova.

13. Oct 10, 2011

### jetwaterluffy

I suppose, but then I think you would have to work out the reflection rate of the craft, because a lot of the radiation might go straight through it, or get used up heating/ ionising the craft.

14. Oct 10, 2011

### Physics quest

Ah ok Twofish, so how do you think I should start? if we take my example of a shuttle and simply assume its entire frontal section taking the blast adds up to roughply 50 meters squared, I am not interested about how pressure works on angles and such at the moment but then, do I just find out how many square meters the supernova explosion covers? (millions I imagine?)

The area of a sphere, or the nova then divide that by the number of meters it affecting to get a percentage or total jouls in the area?

15. Oct 19, 2011

### twofish-quant

Use scientific notation to figure out the order of magnitude.

Exactly.

That will get you some rough numbers, that will get you somewhere to start with.