“Great book to read: Neutron Star by Dr. Forward.”

Wonderful book, but it was called Dragon’s Egg . I also
recommend RocheWorld . Both are excellent books about the
physics of unusual worlds, disguised as novels.

Like I said, both ideas are pretty cool.

Sure are! Metaphorically cool anyhow, the temps may be slightly on the hot side to put it mildly!

So take your pick: giant ice cubes slamming repeatedly at near light-speed into an ultra-compact neutron star and releasing petaton yields of energy somewhere in our galaxy, or a 5.5 billion light-year-distant black widow neutron star consuming its companion star and instigating a supernova event that utterly destroyed both, leaving nothing but rapidly expanding vapor with a tiny black hole at its heart.

Either way, the energies and temperatures and extremes involved are just staggering.

I take it there will be astronomers working on choosing which of these ideas is correct based on other factors and digging through the specific data?

Of course if a similar GRB happens again at the exact same co-ordinates then it’d be very good evidence indeed for the devoured comet theory – now if only we could schedule a second comet to hit say a few months later …

(If only we had FTL craft and could go – very carefully – and see for ourselves. Sigh.)

Emission from very near the neutron star would be so affected, but could be accounted for. Emission from farther out (like from the resulting accretion disk the modelers suggest) would be substantially less gravity red-shifted, but that lack of any spectrum at all right there is hard to account for if the source really was within the few tens of thousands of light-years in our galaxy.

I’m pretty sure that neutron stars have a thin crust of normal matter above the “mantle” of degenerate matter, and that it should demonstrate absorption and emission lines just like any other object. I think the problem is that neutron stars are relatively tiny and quite dim. I’m not sure, but I think that the ferocious surface gravity would also tend to affect redshift measurements.

Gary 7

Both of the hypothesis offered to explain this could account for it, but to my mind if I had to choose between them, there are considerations that persuade me that the more distant binary model is more likely: first, although the collision of a Ceres-sized body with an otherwise isolated neutron star is possible and might account for it, such an event would be quite rare. This coupled with its location in Andromeda, a direction within our galaxy which is not particularly dense in terms of stellar population compared to directions closer to the midline of the galaxy’s plane and especially the central region where one would expect a much higher population of such neutron stars that could in principle do this (Andromeda is looking some 120 degrees away from the galactic center – toward the Milky Way’s OUTSKIRTS) defeats my enthusiasm for this scenario. Further, they’ve reported what seems to be a very distant galaxy detected at the proper location.

I have to favor the extragalactic model, but I would expect more variations of that scenario to emerge as other examples (ultra-long duration + thermal emission) show up. In a general way it already belongs to the basic in-spiraling theme of other (short-duration) GRB theories invoking in-spiraling binary neutron stars and/or stellar-mass black holes. GRB 101225A might represent a new intriguing sub-category in which one of the binary members hasn’t fully moved off the Main Sequence yet.

BTW @50 Lightndattic, etc: it’s been fairly well established in computer simulations that a supernova within a close binary doesn’t necessarily destroy the companion star.

If you know what somethings spectrum is supposed to look like, and you see a spectrum which is shifted into the red a bit, then you can measure that shift to determine the distance.

In this case, however, we don’t know what we’re looking at, let alone what its spectrum is ‘supposed to look like.’ So there is no way to determine how much it has shifted.

There were more theories than there were observations of them! Now we’ve observed hundreds of these things,

Phil, are you using “theory” in the scientifically rigourous sense (i.e. a well-tested encompassing framework that explains various observations, facts as in ‘theory of gravity, evolution’), or in the general sense as in various ideas and thoughts (hypotheses). I’m pretty sure you mean the latter. I mention it because my brother, for about the third time, said “x** is just a theory” even though I’ve explained twice before what is meant by a theory (and then mentioned other theories, like gravity). He just has a hard time understanding it so I’ve been noticing how often even scientists and science-based people also use the word “theory” to mean some sort of nebulous possible idea or even hare-brained (hair-brained?) idea.

**And I say “x” because I don’t want to side-track the discussion.

a marshmallow traveling at that speed would explode like a nuclear weapon.

I love this image!
”
Ban the Marshmallow!

“…they can form a black hole and send vast amounts of gamma rays (super high-energy light) sleeting out into the Universe.”

This may be a silly question, but how do those Gamma Rays escape the black hole? Doesn’t the enormous gravity prevent all light from escaping?

IIUC, as the black hole forms, it is the shock wave travelling outwards through the remainder of the star that triggers the GRB.

We can’t even see the difference between something a couple of thousands of lightyears away and something half-way across the universe? That’s disappointing. Was it too faint or was there not enough time to do a red-shift measurement?

Red-shift measurements rely on absorption lines from the “atmosphere” of a star. IIUC, a neutron star has no parallel to an atmosphere, so there is no matter there to absorb specific wavelengths form the black-body-like radiation that would have come from the impact site.

However, if the GRB was the result of a neutron star entering a red giant, then one would expect to see absorption lines – if one can detect the light of the star in the first place.

IIUC, all that was detected was the gamma radiation.

a marshmallow traveling at that speed would explode like a nuclear weapon.

I love this image!

it’s easy enough to picture: a massive blue star so young that it’s still inside the nebula/cluster in which it formed. imagine that cluster full of other stars, which may have their own sets of planets, as well as free-floating planets and brown dwarfs. if the star goes supernova and forms a GRB, it isn’t hard to imagine the beam hitting one of these smaller objects (if the beam hit another star, i suppose we might never see the beam because there’s enough gas to absorb it) and vaporizing it.

But ok… So they sent the poor schmuck on a suicide mission, somehow knowing that he’d survive and somehow also knowing that he’d come to the conclusion that the Puppeteer home planet doesn’t have a moon. They paid him a buttload of cash to “keep quiet,” somehow knowing that the secret would leak, and that this would throw people off the scent of the planet in question (which is on its way out of the galaxy, anyway). Have I got that right?
Sheesh. I love love love Larry Niven, but I often feel like he just makes it up as he goes along
(In fact, he admits that in the first Ringworld book he didn’t realize that the Ringworld would be unstable in its “orbit”, and that he had to write those stellar ramjets into the second book to account for this)