# How fast are the projectiles from a supernova?

1. Jun 18, 2010

### Gannet

I was wondering for the majority of the projectiles from supernova what would be roughly their velocities. Has anything been determined or theorized?

2. Jun 19, 2010

### nismaratwork

That really depends on what you mean by projectile, and the type of supernova. A somewhat glib answer would be "the speed of light", as photons and neutrinos far outnumber iron or helium molecules being blown out from the shockwave.

3. Jun 20, 2010

### Gannet

After researching I learned the following:

At http://imagine.gsfc.nasa.gov/docs/science/know_l2/supernova_remnants.html"

At http://findarticles.com/p/articles/mi_m1200/is_n18_v139/ai_10808855/?tag=content;col1"

At http://en.wikipedia.org/wiki/Supernova" [Broken]

And various types:
After the researching I have done so far, I would like to create a velocity chart based on Type and Phase.

Last edited by a moderator: May 4, 2017
4. Jun 21, 2010

### twofish-quant

The picture that you should have is a shock wave, and not of projectiles. Everything is a gas, and the fastest things can travel for extended periods of time is the sound speed. Anything that travels much faster than the sound speed will get slowed down with shocks.

More accurately the gas moves roughly at the speed of sound. Near the core the speed of sound is roughly one tenth the speed of light. Once you get into the interstellar medium, the speed of sound drops considerably. The speed of sound is roughly sqrt(gamma pressure / density).

http://en.wikipedia.org/wiki/Shock_wave
http://en.wikipedia.org/wiki/Rankine–Hugoniot_conditions
http://en.wikipedia.org/wiki/Blast_wave

(Also I'll likely be adding something for the Sedov blast wave solution and rewriting the Hugoinot conditions page. Both are cool because you can get a lot with some simple algebra).

Last edited: Jun 21, 2010
5. Jun 21, 2010

### nismaratwork

Yep, that's pretty much how I see it, but again a huge portion of what actually escapes are neutrinos, and photons, which tends to be more "jet-like". Neutrinos in particular are ejected in an asymmetric fashion, but I take your point; this is no volcano tossing "chunks" of star into interstellar space... it's a shock-front followed by "dust". Thanks for the links, and I look forward to your additions to come.

6. Jun 21, 2010

### twofish-quant

That's not likely to be the case. The neutrino and photon fields are a lot more smooth and symmetric than the gas. It's the gas that forms jets. Baryonic matter tends to clump whereas photons and neutrinos tend not to, and so when you do the calculations the neutrinos and photons are a lot more smooth than the gas.

One way of thinking about it, is try to build a doghouse out of neutrons and protons. Not hard. Now try to build a doghouse out of neutrinos or photons. It's really hard to get neutrinos and photons to clump together.

Also internal of the star is optically thick, which means that the photons are pretty much trapped with the gas until the shock wave hits the surface.

They aren't in any of the simulations that I am aware of. There are huge asymmetries but those are mostly in the gas field.

7. Jun 21, 2010

### Gannet

I was hoping to learn about supernova remnants (SNRs) at the chunk (macro) level.

I didn't think to understand SNRs, I had to get into the photons and neutrinos (micro) level.

But like nismaratwork stated
But I do appreciate yours inputs.

8. Jun 21, 2010

### Ich

There's a trick some people use in this forum: if they want to learn about supernova remnants, they ask about supernova remnants. Try it next time.
That said, http://en.wikipedia.org/wiki/Pulsar_kicks" [Broken]is always a good start. I better leave the details for the more knowledgeable people here.

Last edited by a moderator: May 4, 2017
9. Jun 21, 2010

### nismaratwork

I should clarify this, I don't mean that there are polar jets of neutrinos, but that anisotropy in neutrino emission helps to drive the jets you describe. There are asymmetries of the production of flavor of neutrino and oscillation.

http://iopscience.iop.org/0067-0049/163/2/335/pdf/0067-0049_163_2_335.pdf

Asymmetric drift flux...
http://arxiv.org/abs/astro-ph/0307006
http://www.slac.stanford.edu/econf/C0805263/ProcContrib/budge_k.pdf

10. Jun 21, 2010

### twofish-quant

Maybe.

The papers that you've cited suggest this as a possible mechanism, but if you look at more recent simulations by Burrows, the Max-Planck team, and Mezzacappa, it seems that the main drivers of asymmetry are hydrodynamic, and I don't get the sense that the most recent results show that neutrino asymmetries play a strong role in the explosion mechanism.

That's not what Fryer's paper says. What it says is that if you assume that there is an asymmetry in neutrino production and oscillation, then it helps the explosion. He is being very speculative here, but that's what theorists do.

http://iopscience.iop.org/0067-0049/163/2/335/pdf/0067-0049_163_2_335.pdf

Also lots of speculation. Speculation is not a bad thing, but you have to realize that all of these papers are just guessing, and there is nothing firm about any of these. Looking at the more recent papers, I'm not getting the sense that neutrino asymmetry is particularly strong.

11. Jun 22, 2010