
Dual Supernovae Light Up June Nights - Todd
http://www.skyandtelescope.com/observing/dual-supernovae-light-up-june-nights/
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adekok
FYI about Supernovas:

[https://what-if.xkcd.com/73/](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.

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Santosh83
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?

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

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

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ridgeguy
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](https://en.wikipedia.org/wiki/Supernova#Energy_output)

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Retric
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.

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arethuza
Anyone else think of _Look to Windward_?

[https://en.wikipedia.org/wiki/Look_to_Windward](https://en.wikipedia.org/wiki/Look_to_Windward)

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david-given
According to the Culture timeline
([http://theculture.wikia.com/wiki/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!

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saiya-jin
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 :)

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huuu
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.

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HerpDerpLerp
I just want a piece of fairy cake!

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ChuckMcM
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.

