On 18 Apr 2014 at 15:27, Thomas Jones-Low wrote:

> On 4/18/2014 2:46 PM, xxxxxx@shadowgard.com wrote:
> > On 18 Apr 2014 at 7:44, Thomas Jones-Low wrote:
> >
> >> On 4/17/2014 6:20 PM, xxxxxx@shadowgard.com wrote:
> >>> Unlikely.
> >>>
> >>> Thde *neutrino* flux from a supernova will be prompt lethal to humans
> >>> at *Jupiter's* distance. That's 5.2 AU. The flux at 1 AU will be 27
> >>> times higher.
> >>>
> >>
> >> 	These neutrino flux calculations are from the core of the star, not the
> >> surface. So yes, the neutrino flux at 5.2 AU from the *core* of the star is
> >> lethal, but that's still inside the photosphere of a large star.
> >
> > Anything that big won't have planets with life on it. If it's that
> > big and on the main sequence, life never had time to evolve.
> >
> > If it's not on the main sequence, the expansion phase would have
> > wiped out life as planets in the habitable zone first got baked, then
> > got "eaten" when the star expanded past them.
> >
> 	Stars that are not that big won't go supernova. They'll get bigger then slowly
> collapse into a white dwarf star, or perhaps a neutron star. So no neutrino flux
> to worry about.
>
> >> 	For the Antares Supernova project I calculated, based upon known factors of the
> >> supernova and assuming a brown dwarf + planet at a few hundred AU out, the
> >> planet has ~150m of surface melted by the initial light blast. Then cools for a
> >> year or so, allowing a few meters thickness of crust. Then the particle blast
> >> wave hits, remelting the surface and an additional ~100m of crust. This depends
> >> upon distance from the supernova. The paper referenced above should provide some
> >> interesting details on the worlds around the supernova as the gamma ray blast
> >> will have affected them too. In some cases quite badly.
> >
> > Frankly, that sort of thing is about the only way to get a habitable
> > planet close to a supernova.
> >
> > Well, if life can evolve *after* a star in a double star system goes
> > white dwarf and *before* enough matter from the companion (assuming a
> > close binary) accumulates to cause a nova, or supernova.
> >
> > Come to think of it, a binary with a white dwarf that does the
> > *periodic* nova bit might be intereesting.
> >
>
> 	That might be an interesting balancing act. Have the WD companion in a sort of
> close orbit, where it's not pulling a huge amount of material, but some. It
> might be a while before the WD accumulates enough material to go boom. You might
> need to wait for the central star to start expanding at the end of it's life
> before the the WD starts absorbing enough material to be dangerous. That might
> be an interesting system.

Remember, novas are now known to be such systems. And they are
apparently recurring. If the accumulation is slow, you get a nova
every so often. (decades/centuries).

If the WD is too ,massive or the mass transfer is too fast then you
get the WD going supernova. Ouch.

And gee, I bet thereare all *sorts* of intersting minerals on the
surface of the planets in the system.

"Boss, you know the predictuions say we've only got a year or so
before the next nova..."

"Yeah, but we've hit really rich deposits of handwavium. We're making
money hand over fist. And it'll take years after the nova before we
can get these sorts of production levels again!"

"Yeah, but momey's no good if we *die*!"

"But we need to keep producing..."

"Ok, how about we only work the deposits when they are a couple hours
from the terminator on the dark side? That'll protect us if the nova
surprises us, and we could still get into ships and get away in the
plamet's shadow."

"That'd cut production by a third!"

"Given the demand, that'd just drive up the prices.."

"We'd have to move the ships every few hours."

"It'd be a pain, but less of one than getting fried.."

--
Leonard Erickson (aka shadow)
shadow at shadowgard dot com