Did a Neutron Star Create the “Christmas Burst”?


On December 25, 2010, at 1:38 p.m. EST, NASA’s Swift Burst Alert Telescope detected a particularly long-lived gamma-ray burst in the constellation Andromeda. Lasting nearly half an hour, the burst (known as GRB 101225A) originated from an unknown distance, leaving astronomers to puzzle over exactly what may have created such a dazzling holiday display.

Now there’s not just one but two theories as to what caused this burst, both reported in papers by a research team from the Institute of Astrophysics in Granada, Spain. The papers will appear in the Dec. 1 issue of Nature.

Gamma-ray bursts are the Universe’s most luminous explosions. Most occur when a massive star runs out of nuclear fuel. As the star’s core collapses, it creates a black hole or neutron star that sends intense jets of gas and radiation outwards. As the jets shoot into space they strike gas previously shed by the star and heat it, generating bright afterglows.

NASA's Swift observatory is a satellite in low-Earth orbit, scanning the sky for the presence of gamma-ray bursts and gravitational wave forces. (NASA)

If a GRB jet happens to be aimed towards Earth it can be detected by instruments like those aboard the Swift spacecraft.

Luckily GRBs usually come from vast distances, as they are extremely powerful and could potentially pose a danger to life on Earth should one strike directly from close enough range. Fortunately for us the odds of that happening are extremely slim… but not nonexistent. That is one reason why GRBs are of such interest to astronomers… gazing out into the Universe is, in one way, like looking down the barrels of an unknown number of distant guns.

The 2010 “Christmas burst”, as the event also called, is suspected to feature a neutron star as a key player. The incredibly dense cores that are left over after a massive star’s death, neutron stars rotate extremely rapidly and have intense magnetic fields.

One of the new theories envisions a neutron star as part of a binary system that also includes an expanding red giant. The neutron star may have potentially been engulfed by the outer atmosphere of its partner. The gravity of the neutron star would have caused it to acquire more mass and thus more momentum, making it spin faster while energizing its magnetic field. The stronger field would have then fired off some of the stellar material into space as polar jets… jets that then interacted with previously-expelled gases, creating the GRB detected by Swift.

This scenario puts the source of the Christmas burst at around 5.5 billion light-years away, which coincides with the observed location of a faint galaxy.

An alternate theory, also accepted by the research team, involves the collision of a comet-like object and a neutron star located within our own galaxy, about 10,000 light-years away. The comet-like body could have been something akin to a Kuiper Belt Object which, if in a distant orbit around a neutron star, may have survived the initial supernova blast only to end up on a spiraling path inwards.

The object, estimated to be about half the size of the asteroid Ceres, would have broken up due to tidal forces as it neared the neutron star. Debris that impacted the star would have created gamma-ray emission detectable by Swift, with later-arriving material extending the duration of the GRB into the X-ray spectrum… also coinciding with Swift’s measurements.

Both of these scenarios are in line with processes now accepted by researchers as plausible explanations for GRBs thanks to the wealth of data provided by the Swift telescope, launched in 2004.

“The beauty of the Christmas burst is that we must invoke two exotic scenarios to explain it, but such rare oddballs will help us advance the field,” said Chryssa Kouveliotou, a co-author of the study at NASA’s Marshall Space Flight Center in Huntsville, Alabama.

More observations using other instruments, such as the Hubble Space Telescope, will be needed to discern which of the two theories is most likely the case… or perhaps rule out both, which would mean something else entirely is the source of the 2010 Christmas burst!

Read more on the NASA mission site here.


7 Replies to “Did a Neutron Star Create the “Christmas Burst”?”

  1. I wonder what the odds of either of those two scenarios are? I’d hazard a guess that the “icy impactor” scenario happens far more often than the “red giant” scenario.

  2. I wonder what the odds of either of those two scenarios are? I’d hazard a guess that the “icy impactor” scenario happens far more often than the “red giant” scenario.

  3. The impact with the companion star would produce far more energy. The differences in distance, the star impact being at 5.5Bly, while the comet impact is presumed to be 10,000ly. The two scenarios seem to indicate our relatitive lack of knowledge about the source of GRBs. The short pulsed GRBs are thought to be due to the impact of two neutron stars that spiral inwards.

    The icy impact might happen more often, but are locally detectable. Observable star impacts on a sphere measuring billions of light years would be more numerous.


    1. Yeah, I thought about that after I posted:). There are a heck of a lot of neutron stars within 6 billion light-years.

  4. “both reported in papers by a research team from the Institute of Astrophysics in Granada, Spain.”
    Now, I don’t think my colleagues of the other paper, from Italy, would like to see that phrase. 😉 Only one of the two papers was by the IAA Granada (lead by me), the other one was from a group lead by Sergio Campana from the Observatory in Merate (Italy). Believe me, we scientists are bitchy enough on a normal day, imagine the mess we would have with two competing theories *at the same institute*!! 😉

    About the discussion on the probability of one or the other theory, it is actually much less probably that a comet is swallowed by a neutron star than to find a binary system of a massive star and a compact object (and I am not saying that just because I am author of the supernova paper..!). More than half of all stars are not single stars and we know tons of binary systems with a giant star and a compact object, most of them however on more or less stable orbits, but I think it is not totally unlikely to have one that does not have a stable orbit. Infact, as we investigate in our paper, we think that our object might not have been the first “GRB” of its kind. Also, our model is just a model and I would not put my hand in the fire that it is 100% correct, only that it is “something in that style” (but for sure not some comet).
    As for the likelyness of the comet model, also consider where this object is, in case it is inside our own galaxy. It’s not, like most neutron stars, towards the galactic centre, but it is far above the galactic plane in the *opposite* direction, so out towards where our galaxy ends! Now how did it get there? There are no stars being formed at that place so it must have come from somewhere else. Neutron stars can get a kick by their own supernova if the explosion is asymetric. Now how likely is it that something that got a kick from its birthplace carries with it a comet? And even less likely it is that this lonely neutron star in a quite empty corner of our galaxy encounters some randomly flying around small body…

    Enjoy discussing! And fix that thing with the groups 😉

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