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Dual Supernovae Light Up June Nights

skyandtelescope.com

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FYI about Supernovas:

https://what-if.xkcd.com/73/

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Which of the following would be brighter, in terms of the amount of energy delivered to your retina:

1) A supernova, seen from as far away as the Sun is from the Earth, or

2) The detonation of a hydrogen bomb pressed against your eyeball?

A: Applying the physicist rule of thumb suggests that the supernova is brighter. And indeed, it is ... by nine orders of magnitude.

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There are some suggestions that a close supernova would emit enough neutrinos to affect life on Earth. I worked on the Sudbury Neutrino Observatory, for my M.Sc. Roughly, about 10^22 neutrinos go through an average building in a day, and maybe one interacts with the building.

Maybe I'm mistaken, but wasn't the suggestion that a close enough supernova would pose a threat to life on Earth because of gamma radiation and not neutrinos?

The "fun" part is that neutrinos barely interact at all with other matter so the idea of something emitting so much of them than they pose a threat to life is impressive in itself, but sure, it would be the least of our worries if a supernova occured close to earth.

Both.

The neutrino flux can be large. Even if the gamma rays don't get you, the neutrinos will.

Supernovas convert a substantial part of a solar mass to neutrinos. That's a lot of neutrinos.

Yes, it isn't the neutrinos you have to worry about, its the mass of protons traveling at relativistic speed that nail you.

Hiding on the other side of a planet can block most forms of radiation except neutrinos. So, it's not completely irrelevant.

I think our radiation shield wouldn't last long. Back of the envelope, just for fun:

supernova type Ia energy release: ~ 1e44 Joules [1] radius of Earth orbit, m: ~ 1.5e11 meters

diameter of Earth, m: ~ 1.27e7 meters

mass of Earth: ~ 5.9e24 kg

average specific heat of Earth (assume it's all granite): 2,000J/kg/°K

Grinding through the above says that if the Sun went supernova of the wimpiest type, it would dump 1e44 Joules to its surroundings. I think this happens pretty fast, say less than an hour or so.

Assuming isotropic distribution, the Earth would intercept about 4.5e-10 of that, or about 4.5e34 Joules.

That's enough to heat the entire mass of the Earth to ~ 3.8e6°K. That would literally vaporize the entire Earth. There goes our radiation shield.

Never mind the supersonic shock coming through the planet from the ablation blow-off on the side facing the supernova.

Amazing and hard to imagine...

[1] https://en.wikipedia.org/wiki/Supernova#Energy_output

Planets are going to act like an ablative heat shield so it's not quite that simple, however yea even if you survive the initial event it's going to cook any fragments that would otherwise make it. Also, supernova don't just toss out radiation, the kinetic energy imparted to the outer layers of hydrogen is ridiculous.

Awesome. But IIRC even our Sun expanding into its red giant phase should be sufficient to vaporise the Earth, at least according to some models, while other models say everything up to Venus will be vaporised while Earth will be left as a charred lump. More interesting is the case of a supernova within ~100 light years.

There was an interesting article in Scientific American a while ago that the jets from a super massive black hole, from a different galaxy, had the potential to wipe out all life on earth if we passed through the "jet wash". The interesting bit for me was that as the equivalent of a massive solar wind (of exceptional strength) it rips away the atmosphere. That hurts no matter where you are.

Anyone else think of Look to Windward?

https://en.wikipedia.org/wiki/Look_to_Windward

According to the Culture timeline (http://theculture.wikia.com/wiki/Timeline), the Twin Novae battle occurred in 1367, and the light reached (er, will reach) Masaq' in 2170.

(The Culture found Earth in 1977, shook their heads sadly, and then went away again.)

So if we're seeing the light now, that means that we're 649 light years from Portisia and Junce, which suggests that Arm One-Six is what we would call the Orion Arm (the one on which our sun is located). Which means that we were right in the middle of the Culture-Idiran war back in the 14th century. Lucky us!

anytime I imagine those absolutely gigantic proportions of these very violent events, i feel tiny and completely irrelevant in grand scheme of universe. which is exactly how it is :)

Fun fact: a supernova at the Earth-Sun distance would be (quite a bit) brighter than an H-bomb going off while pressed against your eye!

https://what-if.xkcd.com/73/

On the other hand, on the gigantic proportions of the entire universe, even the largest star or blackhole is tiny in comparison. That makes me feel less insignificant because nothing is really significant on a cosmic scale.

I feel the opposite: I also feel tiny but relevant because in this huge space we are (as far as we know it) the only form of life.

I just want a piece of fairy cake!

Gosh I relate to your post and the one you are posting your reply to above.

Some days relevant in the grand scheme, some days totally not.

And that's just one universe. Just think how many more there might be...

It would be so depressing if the peak of alien weaponry is a device that causes a sun to nova, and we are watching an interstellar version of WW III that happened a million years ago as two otherwise intelligent species decided to decimate each other.

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