Home > Science Sidebar, This Is Real > Science Sidebar 1: Things That Go Boom In The Night

Science Sidebar 1: Things That Go Boom In The Night


Since I’m currently working as a science reporting, I’m writing a whole bunch of actual non-fictional things about science.

The catch?  Since the newspaper is not my personal blog, there’s finite space.  So I don’t have room to include all the cool details.  Which made me kind of sad, until I realized that, hey… I could put some of those details on my personal blog.

Life is good.

And thus, this, the first installment, just in time for the Fourth of July.

sn1006c

Courtesy of Astronomy Picture of the Day (who got it with credits to NASA, ESA, and Zolt Levay), here’s SN 1006 — the remnant of a Type 1A supernova. Nice celestial fireworks. (Suffice it to say, don’t set off one of these in your back yard.)

The article I’m referring to is available online here.

So, what didn’t make it into the article?

Details about how explosions work.

There are essentially two different ways for stuff to burn: deflagration and detonation.

Deflagration is seen in low explosives, like gunpowder.  When heated above its ignition temperature, low explosives will burn.  If you heat up one part, the burning from that part can heat up the next section to ignition, which gives you fuses or fireworks that go off in sections.  If you really want something to go boom, you’ll need to contain it as it burns, letting the build up of hot gases as stuff burns do the work for you.  Critically, the burning from deflagration propagates through the material slower than the speed of sound in the material.

Detonation is characteristic of high explosives, like nitroglycerin.  In these cases, the burning goes supersonic, sending out a shockwave… which can be enough to set off high explosives all by itself.  These things are fricking dangerous, for the most part.  So don’t even think about working with them unless you’re a chemist or pyrotechnics expert and you know what you’re doing.

I knew about these two things before I did the research for the fireworks article.

Why did I know?

Because the transition from deflagration to detonation is important when studying supernovae.

Oh, yes.

In Type 1A Supernovae, a white dwarf star goes kaboom.  The precise mechanism for the kaboom is a topic of some debate, but the most widely held position is that the white dwarf is in a binary system with another star, most likely a red giant.  The white dwarf is already the small, core remnant of a star that can no longer sustain nuclear fusion — something roughly the mass of the Sun, compressed to be the size of the Earth.  Without its nearby neighbor, it would just fade away to a cold dense lump of stuff.

But it has a neighbor — and if that neighbor is close enough, the white dwarf can steal its gas away.  The white dwarf eventually consumes more mass than it can hold and still be a white dwarf.  At this point, something happens near the white dwarf’s core: fusion reignites.  This fusion flame starts a chain reaction, which ends with the white dwarf completely fusing and generally blowing itself to bits.  Oops.

Exactly how this explosion proceeds is an active area of research, complete with really awesome graphics and big computer simulations.  One of the open questions is whether the resulting explosion and blast of light and neutrinos is driven by deflagration or detonation, or a combination of the two.  The speed of sound is really fast in something as dense as a white dwarf, so it can be a bit tricky; plus, the combination of needing to cover fusion and radiation and heating and fluid flow makes it pretty tough to simulate.

That being said, white dwarfs are blowing up all the time.  (Also, for a sense of scale — at its brightest, a Type 1A supernova is around 5 billion times brighter than the sun.  Which is a lot brighter than your backyard fireworks.)

So, to you astronomers out there: Happy Fourth of July.

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  1. michaelbusch
    2014/07/03 at 7:27 am

    For an additional discussion of just how big a boom a supernova is, refer to Randall Monroe: http://what-if.xkcd.com/73/ .

  1. 2016/03/25 at 10:51 pm

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