From: The Low Golden Willow (phoenix@ugcs.caltech.edu)
Date: Fri Jul 04 1997 - 00:31:33 MDT
On Jul 4, 7:40am, Eugene Leitl wrote:
} Gamma rays at the density of lead (which are opaque to gamma ;), flying
} towards us at about 0.99 c. So somebody is throwing chunks of solid gamma
} at only slightly subliminal velocities. As even puny supernovas generate
Gamma rays... these would be photons, yes? "Slightly subliminal"? I'm
having a problem here.
} lethal neutrino (!) flashes in a couple of LYrs range (according to Damien
} Sullivan, also of the extropian fame), a GRB should fry a sphere of some
If I didn't say, I should have said: the figures I saw were in the AU
range; Earth's orbit, or maybe Jupiter's. Carl also noted that his GRB
energies were less than that of supernovae, although the numbers below
look bigger.
No, they use ergs, and I think Carl used watts. Or Joules. I forget.
In other words, we should be grateful if most of a supernova's energy
goes into neutrinos. But I'm not sure what "most" means. 50%? 90%?
99%? A factor of 2 or 3 isn't that much, and implies that GRB's aren't
galactically deadly, since their gamma output would be equivalent to a
supernova, and we've had lots of those in this galaxy. Not near by, but
they haven't sterilized everything. (Unless that's the Filter, and
we're the lucky ones.)
Guessing wildly that a supernova is deadly within 100 ly, if a GRB had
100 times the gamma output that would give 1000 ly killing radius. (I'm
assuming inverse square applies.)
Urrrn. If supernovae are deadly in 100 ly, shouldn't Sirius be frying
us in a few million years?
Perspective: the main shock seems to be that we see these GRBs from
across the universe. But I've heard that supernovae can outshine their
host galaxy. If a galaxy is visible from across the universe then so
are supernovae, and these GRBs aren't that big a deal. They're just
different and purer.
Or perhaps more frequent, since I haven't heard of a supernova every
week.
} > > satellite BeppoSAX indicate the source of the GRB is extra-
} > > galactic at a distance of 5 billion parsecs (about 20 trillion
16 billion light years! Do Hubble constant calculations agree with
this? Not to mention cosmo-evolutionary models? Although the stars
that form neutron stars and black holes don't last very long, once
formed.
Hypothesis: massive first generation of stars. All go supernova and
make neutron stars. Sometime later, neutron stars run into each other.
Boom. If we'd been earlier we'd have seen lots of supernovae scattered
around the universe; we're later, so we see the second movement of the
death-dance. Happily surrounded by red dwarfs ourselves.
} > > an initial energy burst with a magnitude equal to the total
} > > radiation from our Sun during the entire age of the universe. The
} > > computed energy figure is 10exp51 ergs of gamma-rays. A consensus
Cross-posted to extropians for maximum criticism.
Reliability: low. I trust the supernova-neutrino calculations. I
careened on the comparisons.
Merry part,
-xx- Damien R. Sullivan X-) <*> http://www.ugcs.caltech.edu/~phoenix
"The really ironic issue of late has been supercomputer exports. We now
have the spectacle of William Reinsch saying that export restrictions
on supercomputer *hardware* are unworkable because the technology is
available all around the world.
This is the very same Commerce official who still says with a straight
face that export controls on encryption *software* are workable and
desirable."
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