Micro neutron star versus nano comet versus mega red giant

By Phil Plait | December 1, 2011 10:50 am

If you’re a fan of over-the-top ridiculously huge violent explosions, then you won’t do any better than gamma-ray bursts. With apologies to Douglas Adams and Eccentrica Gallumbits, GRBs are the Universe’s largest bangs since The Big One. When they were first discovered, during the Cold War, it was unclear what caused them. There were more theories than there were observations of them! Now we’ve observed hundreds of these things, and we’ve learned quite a bit about them, like a) every one of them is different, 2) they have lots of different sources, and γ) even after five decades they can still surprise us.

Last year on Christmas, the light from a gamma-ray burst reached Earth and was detected by NASA’s orbiting Swift satellite. Designated GRB 101225A, it was weird right off the bat: it lasted a staggering half hour, when most GRBs are over within seconds, or a few minutes at most. Followup observations came pouring in from telescopes on and above the Earth, and the next weird thing was found: the fading glow from the burst seemed to be coming from good old-fashioned heat: some type of material heated to unbelievable temperatures. Usually, the afterglow is dominated by other forces like rapidly moving super-intense magnetic fields that accelerate gigatons of subatomic particles to huge speeds, but in this case it looked like a regular-old explosion.

Both of these things are pretty dang weird. So what could have caused this burst?

Normally, we think GRBs are the birth cries of black holes. When a giant star explodes, or two tiny but ultra-dense neutrons stars merge, they can form a black hole and send vast amounts of gamma rays (super high-energy light) sleeting out into the Universe. In this case, though, something different happened, and two ideas of what was behind it are emerging…. but both involve neutron stars. And I’m not sure which idea is cooler.

First; neutron stars are extremely dense balls of matter only a few kilometers across, the collapsed remnants of the cores of stars that went supernova. By dense, I mean dense: imagine taking a mountain and crushing down in size to where it could fit in your hand! Or think of it this way: a cubic centimeter (roughly the size of a sugar cube or dice) of neutron star material would have about the same mass as all the cars in the US combined! So we’re talking dense.

The gravity of a neutron star is nearly beyond comprehension. If you let something drop from a height onto the star’s surface, that material will be moving at a large fraction of the speed of light upon impact! The energy release is monumental; a marshmallow traveling at that speed would explode like a nuclear weapon.

And that brings us to the first idea: a comet or other large chunk of material was orbiting a neutron star. It got too close, broke apart, and fell on the surface. As each piece hit it released far more energy than all the nukes on Earth combined — by a factor of millions! — sending out huge amounts of light into space. That explains both the flash of the GRB detected last year and the fact that the afterglow was in the form of heat; the vast energy of the repeated slamming impacts of the comet chunks would’ve heated the material (and the neutron star) to millions of degrees.

So, yikes.

If this is the case, it happened in our own Milky Way galaxy. As huge as the explosions were, they would’ve faded to nothing had they been in another galaxy, so on a cosmic scale they must have been relatively nearby. But there are bigger bangs to be had…

… and the second idea to explain GRB 101225A is no less amazing. In that scenario, a neutron star was orbiting a normal, if older and somewhat bloated star. As the normal star expanded, it engulfed the neutron star, which then started eating up the material around it. Again, huge amounts of energy were released, heating up the normal star’s outer layers so much they eventually blew off the star. In the meantime, though, friction with this material dropped the neutron star down to the normal star’s core, which at this point was mostly helium (having had a normal life for billions of years fusing hydrogen into helium). At some point, the neutron star crashed right into this helium core, and that ginormous amount of material — the mass of our own Sun or so — slammed into the neutron star’s über-dense matter.

Mind-numbingly powerful gravity would’ve squeezed that stuff as it fell on the neutron star, and the gravity became so intense not even the neutron star-stuff could resist: the neutron star itself collapsed into a black hole, releasing a flash of energy focused into two tightly-focused beams that lasted for a few seconds, equal to the Sun’s total lifetime of energy release! This wave of energy slammed into the material previously ejected from the normal star, heating it and causing the long afterglow seen last year.

If this is the case, the cosmic bomb was farther away than the comet scenario; it would’ve been in a galaxy billions of light years away, far enough to dim even that titanic explosion to something we wouldn’t even had noticed unless we had satellites orbiting the Earth, keeping a watchful eye on the sky.

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.

See? Like I said, both ideas are pretty cool.

NASA helpfully has created a nice video with animations for the two possible scenarios:

But which is correct? It’s hard to say. Both ideas have their plus and minuses. Usually dueling ideas like this take more observations to figure out, but in this case it was a singular event, so that’s not really possible. But better models, better understanding of physics, and better analysis of the original data may yet rule on this split decision. And who knows? We’re still scanning the skies, and may yet see another event like this. If we do, that will help us understand such baffling phenomena. Heck, earlier this year we saw a black hole shred up and eat a star, so clearly the Universe has some pretty hefty tricks still left up its sleeve.

Images credits: NASA; NASA, ESA, H. Weaver (APL/JHU), M. Mutchler and Z. Levay (STScI); NASA


Related posts:

Astronomers may have witnessed a star torn apart by a black hole (with Followup 1 and Followup 2)
Cosmic X-ray blast temporarily blinded NASA satellite!
Most distant object ever seen… maybe
Anniversary of a cosmic blast

CATEGORIZED UNDER: Astronomy, Cool stuff, Top Post

Comments (60)

  1. The more we study the Universe, the weirder and weirder it seems out there. Luckily, I’m a big fan of “weird”!

  2. Chris

    Micro neutron star versus nano comet versus mega red giant

    Sounds like a new miniseries on SyFy!

    As for the comet idea, this sounds like it could be a common occurrence, so why don’t we see more of these?

  3. Michael

    “If you let something drop from a height onto the star’s surface, that material will be moving at a large fraction of the speed of light upon impact!”

    If dropped from what height? Like from waist height, or building height, or cruising airplane height? Just how much acceleration is at work here? Or is it soooo much that it hardly even matters?

  4. Renee Marie Jones

    It is probably just the closing chords of a Disaster Area concert.

  5. And it’s things like this that have kept me interested in astronomy all these years. Pretty dang cool indeed.

  6. If it was a comet that fell onto the neutron star, then shouldn’t GRBs like this be a common occurrence? I am sure that there are many neutron stars out there with comets flying around them and I could see this happening kinda often.

    I saw that there may be something like a billion neutron stars in our galaxy, are they just too old and not have enough stuff orbiting them to have material crash in on the star?

    Also, if something falls in on a neutron star will a GRB be omnidirectional or only fly off in the direction of the magnetic poles?

    If it was the latter, because the GRB lasted for so long, then the poles would be pointed at us and couldn’t we just monitor the area for any additional debris falling onto the star?

  7. Jay

    @Michael (#3): “If dropped from what height?” Questions like that can be answered with a little math. First a few assumptions: (a) To make the equation easier to solve, assume the acceleration is constant. (It really isn’t, because a neutron star’s gravity field falls off as the square of the distance from its center, but the full treatment requires calculus.) (b) Assume the object starts from a nearly circular orbit, so the initial speed in the direction of the neutron star is near zero. (c) Assume the acceleration (surface gravity) of the neutron star is 3 x 10^12 m/s² (an average value according to Wikipedia). (d) Let’s say that a “large fraction of the speed of light” is 0.3 c, but let’s still ignore any relativistic effects.

    The equation to use is v² = 2ar, where v is the final (nonrelativistic) velocity, a is the acceleration, and r is the initial distance (http://en.wikipedia.org/wiki/Kinematics#Kinematics_of_constant_acceleration). Plugging in the values and solving for r yields r ~ 1.6 x 10³ m or about 1 mile.

  8. Gwif

    You had me at Eccentrica Gallumbits.

  9. OK, “a) …, 2) …, and γ) …” is just about the most wonderful list I’ve seen

  10. Endyo

    @zAmboni, I was thinking the same thing. Comets hit the Sun all the time. The gravitational field of a Neutron star can’t be much smaller than the Sun’s…

    However, I can imagine that the Supernova that created the star might blow most commets away or vaporize them…

  11. MadScientist

    I thought it was the planet Krypton exploding as its star burnt out.

  12. DrFlimmer

    @ #6 zAmboni and #9 Endyo

    Well, even if we assume that almost all comets stay in orbit around the neutron star (I guess Endyo is right that many are either vaporized or blown away) the number of them actually crashing onto the neutron star should be rather low.

    Remember: Compared to a neutron star the sun is BIG! (a few km compared to 1 million km !!) So the odds of a comet with a highly eccentric orbit crashing into the sun are quite high.

    On the other hand, in order for a comet to come THAT close to the neutron star it has to have either a VERY eccentric orbit (which would be more or less a straight line, i.e. radial impact which is really unlikely) or it has to lose quite a lot of its angular momentum, which is also a problem.

    Thus, I believe (without making any calculations) the odds of a comet hitting the surface of a neutron star should be fairly low.

  13. Ken

    So what could have caused this burst?

    Please say exploding hyperdrive, please say exploding hyperdrive…

    two ideas of what was behind it are emerging…. but both involve neutron stars

    Darn.

    Endyo @9: Remember also that although the gravity of a neutron star may be similar to that of the Sun, you can get a lot closer to the neutron star. I was reading a book just last week that made that point….

  14. Tom Ames

    Can we see it there is a galaxy at the same coordinates as the GRB? (Or is it the case that if you look out far enough–billions of light years–there’s very frequently a galaxy at ANY given coordinate?)

  15. GebradenKip

    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?

  16. Dan the man

    What if what we saw was our own earth being born, in some cosmic parallel universe.

  17. Herazod

    I am not an astronomer or astrophysicist, but I think it would be a big difference between a comet hitting a main sequence star and a “dead” neutron star.

    I would assume that the comet would be burned off before ever getting close enough to a main sequence star to make any sort of explosion. They may have similar sized gravitational fields, but much different densities. there isn’t a photosphere on a neutron star.

    given that they are also MUCH physically smaller, it would follow that it would be MUCH less likely to hit eachother.. things in orbit tend to stay there unless disrupted by something else.

    if this was a comet, it was likely a large one and wasn’t from orbit degradation, since that would likely tear apart any large object from the tidal forces long before it stuck the star itself.

  18. Dave

    Ken – Can’t speak to the hyperdrive, but it’s common knowledge that the fusion explosion of an impulse engine generates a mere 97.835-megaton explosion. I suppose the hyperdrive would generate a bigger bang but nothing like this!

  19. A Cosmological Fantasia has made me come to expect much better animations than these.

  20. andy

    Would be a great way to set up a beacon to contact aliens across a large region of the galaxy: set up a string of asteroids to crash into a neutron star at specific timings, then flee the neighbourhood and watch the fireworks.

  21. Jonathan Latimer

    “…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?

  22. Whomever pointed out that neutron stars are small hit it on the head. The reason the sun is hit more frequently is because it has a much larger cross section. If you assume that there is the same amount of stuff as in the Solar System as there is around a neutron star, the odds of a neutron star impact would be a few billion times less frequent (R_sun/R_neutron)^2. And supernova explosions should get rid of a lot of material, but they can also have fallback disks that form planets and maybe also asteroids/comets. But I would think that if it was the alternative explanation, someone would be able to look for the red giant star in deep Hubble/groundbased imaging.

  23. Dragonchild

    Neutron stars may be my favorite phenomenon in astronomy. They boggle my imagination.

    @16. GebradenKip –
    “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?”

    Considering they’ve gotten spectrums of much shorter GRBs, I’d say the odds are pretty darn good they got the spectrum of a half-hour “burst”. That’s a starting point for a redshift measurement. The problem here is there’s nothing to redshift against! Most distant objects (namely galaxies) that have been successfully redshifted are based on a foundation of “standard candles”, namely type 1A supernovae — they’re common (in a relative sense), very bright, we’ve worked out the relation between luminosity and distance and they’re all very similar, so after a while you can build up a profile with which to determine distance due to redshift alone. For phenomena within our galaxy we typically try to observe nearby stars and determine their distance based on luminosity and spectral type — again, standard candles. This particular GRB is (as of now) unique; it doesn’t correlate with any previously observed phenomenon. Trying to redshift it is analogous to our ancestors discovering planets in a single naked-eye observation — without telescopes or logging their path across the sky they have no means of comparing planets and stars; they look identical.

    Right now this thing is so different from anything else that as of now they have no idea what to redshift to. I’m not an expert, but in the coming weeks I’d bet they’ll check that part of the sky again. Finding a pulsar there would be strong evidence it was a nearby neutron star that got punched by a comet. Otherwise they’ll mathematically work out the luminosity of the “neutron star blows up another star” scenario, combine that with the measured brightness of the GRB, get the estimated distance and look for an appropriately redshifted galaxy in that direction. I’d say they know what to look for, but in the meantime we have to be patient. Problem is that a neutron star being a pulsar is NOT a sure thing and otherwise neutron stars are difficult to find, and distant galaxies are so numerous (remember Hubble Deep Field?) that you’ll probably find one in that part of the sky if you look hard enough even if it had nothing to do with the GRB. But at this point I’m speculating so I’ll shut up now.

  24. Dragonchild

    @22. Jonathan Latimer Says:

    “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?”

    The black hole itself is quite boring in some respects because, as you say, nothing escapes it. Unlike a neutron star’s crust, the event horizon isn’t a surface so there’s no colliding with it — you slip through and you’re lost forever. The exciting stuff happens on the OUTSIDE of the event horizon. Near the event horizon black holes still have tremendous gravity, far stronger than a neutron star’s. Stuff around a black hole is still being ripped apart, ground into subatomic particles and heated up to silly temperatures by tidal forces that would make a neutron star blush.

    It’s outside the event horizon where the gamma rays are created, and even though they’re far enough out to escape the gravity, that doesn’t mean they aren’t twisted and tortured as they leave. IIRC much of the light is focused into intense narrow jets and redshifted by the stupidly strong gravity. By comparison our sun just coughs up a flare (that can damage electronics 100 million miles away) when it’s in a BAD mood.

  25. Eric

    @14. Ken

    “So what could have caused this burst?
    Please say exploding hyperdrive, please say exploding hyperdrive…”

    I was thinking exploding Tardis, but then that would probably have destroyed most of the universe.

  26. Kurt Erlenbach

    I have exactly the same question as GebradenKip #16: I don’t understand the difficulty of figuring out if the GRB was within or without the galaxy. Why wouldn’t a redshift measurement make that distinction?

  27. Jonathan Latimer

    Ah, thank you Dragonchild — a very good explanation!

  28. Yoweigh

    @Ken #14
    What can kill you through a General Products hull?

  29. @#6 zAmbon: If it was a comet that fell onto the neutron star, then shouldn’t GRBs like this be a common occurrence? I am sure that there are many neutron stars out there with comets flying around them and I could see this happening kinda often.

    Ah yes, the classic philosopher’s quandary: “If a comet falls onto a neutron star at relativistic speeds, and no one is around, does it make a gamma ray burst?”

    @#29 Yoweigh: What can kill you through a General Products hull?

    Heh, I love that story, but I still find it highly unlikely that a species as technologically advanced as the Puppeteers can’t figure out something as basic as tidal effects, moon or no moon.
    That said, I’d love to take that particular trip (assuming I could reliably prevent myself from being ripped apart or turned into a puddle of goo in a corner of the hull).

  30. @14. Ken
    >>“So what could have caused this burst?
    >>Please say exploding hyperdrive, please say exploding hyperdrive…”
    I was thinking exploding Tardis, but then that would probably have destroyed most of the universe.

    Maybe it was a massive Warp Core breach? Antimatter produces gamma rays when annihilating against matter. Maybe it took so long because the Borg popped a whole Federation fleet one after the other.

  31. Yoweigh

    @30 Joseph
    That was a ruse. The Puppeteers know all about tides. Have you read the Fleet of Worlds books?

  32. Sam H

    I find the neutron star-core collision hypothesis making more sense here IMO, but in the case of the comet: if that would be vaporized, then how about the collision of a whole planet instead? It would get torn to pieces similarly, and planets are far more massive than comets. Perhaps its orbit was unstable, and it had been spiralling toward the neutron star until it finally collided.

    (For the more mathematically capable of you): how does that sound??

  33. Cosmonut

    Second scenario is way cooler.

    Piddly little comet versus humongous red giant. Tame intragalactic event versus colossal hypernova that can be scene across billions of light years. Plus a black hole being created as a bonus.

    Absolutely no comparison. :)

  34. mfumbesi

    The Widow killer is more appealing. For a moment I was on this ride when you described the sequence of events leading to the destruction of the second start. Man that was some awesome trip…..

  35. @#32 Yoweigh: Ohhhh. Tanj it, that’s pretty damned circuitous.
    I have read several, but I can never keep track of all of them. I keep coming across more Niven books and stories that I’ve somehow missed.

    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 :D
    (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) ;)

  36. QuietDesperation

    And then the UberSharktopus came along and pwned them all.

  37. Fizz

    For the first idea, wouldn’t this happen all the time? Things crash into the sun all the time, so there are probably plenty of things to crash into neutron stars. I guess their smallness and rareness would make it a rare occurrence, but the galaxy is pretty big.

  38. Jim Rix

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

  39. chris j.

    why aren’t we talking about a third possibility, that the glow came from something that happened to lie in the beam from the GRB?

    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.

  40. Nigel Depledge

    The BA said:

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

    I love this image!

  41. Nigel Depledge

    Gebraden Kip (16) said:

    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.

  42. Nigel Depledge

    Jonathan Latimer (22) said:

    “…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.

  43. That_Guy

    “The BA said:

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

    I love this image!

    Ban the Marshmallow!

  44. Mephane

    I understand this is interely speculative, but as someone with a heavy interest in science fiction I must add: what if some of the weirder astronomical observations were actually observation of something of artificial nature. Like, a superweapon, a giant starship going haywire, maybe a large-scale scientific experiment? I am not saying any observation is supposed to be something like that, I am merely musing on the notion – what if? Heh.

  45. Daniel J. Andrews

    I hadn’t realized a comet would release that much energy…love the marshmallow comparative reference. Run away….he’s got a marshmallow!

    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.

  46. Peter Davey

    The author, Stephen Baxter, in his book, “Space”, paints a picture of the universe as teeming with life. However, at the point when the life become sufficiently advanced to start exploring space, radiation from Gamma -Ray Bursters wipes out all but the most primitive life-forms, leaving the whole process to start again, giving a new meaning to the term “vicious circle”.

  47. Robert

    @27 “Why wouldn’t a redshift measurement make that distinction?”

    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.

  48. ColinC

    Just a quick question for the more science skilled than I, but if this was the comet explanation, how fatal would this have been to nearby star systems? Would this be another Death from the Skies event? Does this form of GRB propogate from that even in a beam or a halo?

  49. Lightndattic

    Adding to what Endyo and John mentioned, how would a neutron star be orbiting another healthy, albeit older, giant stage star? Wouldn’t the supernova that created the NS in the first place destroy any companion star close enough to have it’s expanded material later gobbled up by the NS? It’s always been my impression that a supernova would destroy everything or at least almost everything within it’s local area of space. Would this need to be a case of a wandering NS encountering a neighbor star?

  50. Anchor

    The main features that makes GRB 101225A so weird, as Phil says, are the long duration (a half hour’s worth of gamma ray emission, although some have been observed to last a bit longer than a few minutes) and the apparent thermal component (as opposed to the usual synchrotronic emission, characteristic of charged particles being violently deflected or accelerated in a strong magnetic field).

    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.

  51. Gary Ansorge

    Hey, guys, that GRB was a message to me,,apparently my ship is out of dry dock and on its way home,,,

    Gary 7

  52. Anchor

    @50 Lightndattic, etc follow-up: It is also interesting that supernova explosions often provide a ‘kick’ to the resulting compact remnant (a neutron star or black hole) which in this case may have set up the circumstances (a significantly elliptical orbit) for this particular neutron star’s demise once the companion swelled large enough for its outer atmosphere to snatch it during its periastron passages…

  53. @42 Nigel Depledge: 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.

    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.

  54. @53 Gary Ansorge: Hey, guys, that GRB was a message to me,,apparently my ship is out of dry dock and on its way home,,,
    They deliver? That’s nice. I was gonna say, if you’re looking for a ride to the dealership, good luck ;)

  55. Anchor

    @Gary: If its headed this way I’m just glad it’s decelerating.

  56. Anchor

    @Joseph G.: “I’m not sure, but I think that the ferocious surface gravity would also tend to affect redshift measurements.”

    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.

  57. Messier Tidy Upper

    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. 8)

    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.)

  58. llewelly

    39. Jim Rix Says:
    December 2nd, 2011 at 1:27 am:

    “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.

  59. Abigail Michell

    Hopefully one day we can go there and look at the aftermath ourselves, with our own eyes.

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