A star is torn

May 29, 2011 • 8:05 am

The Guardian reports evidence that a very distant star—more than 13 billion light years away—has exploded violently.  This is about a quarter of the distance between Earth and the edge of the observable universe, which is about 46 billion light years. (Go here to learn about the difference between the size of the universe and the size of the observable universe, and why—although the universe was formed about 14 billion years ago, and objects can’t move faster than the speed of light—the observable universe is nevertheless 93 billion light years in total diameter.)

The significance?

Andrew Levan, one of the scientists behind the discovery, said this blast from the past blew open a window onto the universe’s early years, showing that massive stars were already dying within the first few hundred million years of the birth of the universe.

This particular explosion wasn’t a supernova but a gamma ray burst, the name given to a short but powerful pulse of high energy radiation. Such bursts, thought to result from the collapse of massive stars into black holes, shoot jets of energy across the universe. [Read about those bursts here.]

And this is mind blowing:

Charles Meegan, a NASA researcher in gamma ray astronomy, said that a typical burst “puts out in a few seconds the same energy expended by the sun in its whole 10 billion year life span.”

Those bursts of gamma rays last only a few seconds to a few minutes, so when astronomers were told of the explosion, they had to leap from their beds to collect data on the “afterglow.” And even then it took two years to analyze that data, which, according to team leader Andrew Levan at the University of Warwick, shows “with 90 percent certainty that the gamma ray burst had been spotted between 13.11 billion and 13.16 billion light years away.”

Some colleagues are less certain.  Richard Ellis, an astronomer at Cal Tech, said, “This is plonk at the frontier, where we have very little idea what’s going on. ”

h/t: Matthew Cobb

71 thoughts on “A star is torn”

  1. If this happened in our neighbourhood, at a distance of a dozen of light years or so, we would find out in a millisecond whether there is an afterlife or not.

      1. “If this happened in our neighbourhood, at a distance of a dozen of light years or so, we would find out in a millisecond”

        How so, if gamma rays propagate at the same speed as other electromagnetic radiation?

        1. Yes, of course. When we spot a supernova, it probably happened a long time before you were born. If you get a sunburn, the UV rays took 8 minutes to reach you. Gamma rays can be deadly even if they traveled 20 years.

          1. “we would find out in a millisecond whether there is an afterlife or not”

            That’s incorrect.

            We would ONLY find out that there is an afterlife, if there, indeed, IS an afterlife. If there is NO afterlife, we will not be in a position to realize that, so there will be no finding out.

          3. “When we spot a supernova, it probably happened a long time before you were born.”

            Thanks, man, it’s not that often anymore that somebody mentions stuff that happened before I was born. And speaking of before-I-was-born, I’m thinking the afterlife is gonna be a lot like that.

          4. Yes. I sometimes imagine that in a former life I must have been a Roman soldier, conquering Europe, but having plugged off, I lost all memory of this.

        2. Astronomers count time in the observer frame. I.e. Earth time.

          So it is correct to say that we would find out.

          But only if the GRB jet was pointed directly at us; a rather narrow object.

          1. Duh! So it is correct to say that we would find out within seconds.

    2. Luckily, a gamma-ray burst like this one is a very beamed explosion, which is how we see them from so far away. There’s enough galaxies in the universe that we see stars explode with alignments right to beam stuff at us. While a supernova is nothing to sneeze at, it’s a lot less intense than being in a GRB’s beams.

      If one went off in our galaxy, it would most likely look like a normal supernova since it probably wouldn’t be aligned with us staring down the pole. Which is much less threatening, since we know the stars in the danger zone and none of them are exploding soon/at all. We’d have to be extraordinarily unlucky for a GRB to be beamed at us from close enough to matter.

      Sorry, one of my contractual duties as an astronomy grad student is to discourage astro-doomsday predictions. For asteroids I break out the capslock, even.

      1. Right! And after all, the greatest show on earth lasted for nearly 4 billion years already.

        I suppose a GRB would have meant a big reset and would’ve blown away the atmosphere.

      3. Thank you!

        You would think religion would have taught people the problems of inventing doomsday scenarios. But nooo…

      2. I see Sarah Palin has bought a house in Arizona Ben – will you lose sleep over that?!

  2. Amusing headline.

    Reading about large, distant space objects always gives me the feeling that my mind is standing on tip-toes, try to grasp something that’s out of reach.

  3. Mind you, the YEC crowd will declare this another example of their god laying another trap for the ungodly, fooling the ‘wise’ into thinking that anything is farther off than their 10,000 year horizon.

  4. Correction: The star exploded 13.1 billion years ago. Since the universe is 13.7 billion years old, this event occurred when the universe was only about one twentieth of its current age.

    The light from this explosion has taken 13.1 billion years to reach us, but the star was not 13.1 billion light years away when it exploded, it was much closer. As the light was traveling towards us, the universe was expanding, so it took 13.1 billion years to cover what was originally much less that 13.1 billion light years of distance.

    Similarly, whatever remains from this explosion is now much farther than 13.1 billion light years away.

    For events that occurred billions of years ago, it is best to just give the time. The distance doesn’t really mean anything.

      1. In fact, 13.1 billion years ago when the GRB occurred, that region of space was already receding from the region of space that we now occupy (“us”) at greater than the speed of light; and its rate of recession has steadily increased since then. As Gavin said, 13.1 billion years ago the GRB was much less than 13.1 billion light years away; it is now much more than 13.1 billion light years away, somewhere close to the edge of our observable universe.

        When the GRB emitted these photons, they initially moved away from us, because their local velocity (the speed of light) was less than the superluminal recession of that region of space.
        However, the expansion of the universe initially decreases due to gravity, so the photons eventually moved into a region that was receding from us subluminally. They photons then began moving towards us, and eventually reached as.

        There is an excellent paper by Davis and Lineweaver written in fairly accessible language, freely available online by Googling “Expanding Confusion: common misconceptions of cosmological horizons and the superluminal expansion of the universe.”

        1. That one is on my reading list. Now I have a good reason to pop it up.

    2. I guess it has also in the meantime receded beyond our event horizon, so that the explosion remnants are no longer in our observable universe. So, no point in making travel plans to check it out.

  5. How can it be that the universe is 93 billion light years in diameter if it’s no more than 14 billion years old and nothing can travel faster than the speed of light? How does that work? Is there anything I can read that explains how that occurred?

    1. “How can it be that the universe is 93 billion light years in diameter if it’s no more than 14 billion years old and nothing can travel faster than the speed of light?”

      Nothing can travel faster than light means that no-*thing* can travel faster than light, and thus that no energy or information can be transferred from one bit of space to another at faster than light. However, it does not prevent space stretching such that the separation between two regions of space increases at more than light speed.

      1. Ahhh…my brain has the faintest ticklings of grasping this…so during inflation, “empty” space expanded ftl, but not matter?

        1. “… so during inflation, “empty” space expanded ftl, but not matter?”

          The matter is stationary within its local space, but the space is expanding. So distances between two bits of matter can increase ftl, but nothing is traveling from one bit of space to another at ftl.

          1. I had understood that matter remains stationary within expending space, I just never made the connection of the space between objects expanding ftl. Also, was I incorrect in thinking this happened only during inflation?
            From my very limited understanding, isn’t space at the edge of the observable universe expanding at a great portion of C, at least from the extreme redshifts we observe?

          2. No, locally space is expanding very slowly. It is the accumulation over astronomical [sic!] distances that eventually makes recession (as we see it) superluminal.

            If Ralph’s reference above is too hard to digest at first go, have you looked at the Wikipedia cosmological articles?

          3. Oops, I forgot:

            Yes, it is incorrect to peg this at inflation. It is the local expansion taken over the global scale that makes us see superluminal recession.

            Inflation was an expansion, and very fast. But as for its effect on the specific question of recession, it looks much the same as the dark energy expansion that characterizes the later periods of our universe.

            From a technical note (i.e. not as accessible) of Davis & Lineweaver:

            “Exponential expansion, such as that found in inflation, has q = −1.
            Therefore the Hubble sphere is at a constant proper distance and coincident with the event horizon.
            This is also the late time asymptotic behaviour of eternally expanding FRW models with
            Omega_Lambda > 0”

            In essence, inflation and late time behavior of our universe have essentially the same effect here.

          4. “Expending”? OMG. Stoopid typos. Thank you for your responses! I thought the event horizon was the point at which a black hole’s gravity “traps” light – one would observe an object at this point never actually “falling” into the black hole as the information (light) past that point would not be able to pass the event horizon. So yeah…that “technical” bit is like reading Japanese to me lol! I can only follow the wikis to a certain point before it gets beyond me. It’s a cruel thing that I have such an interest in cosmology but little capacity to grasp it 🙁

      2. And “nothing can travel faster than light” isn’t even accurate for ‘things’ (including energy and information). They probably can! It’s just that these ‘things’ can’t CROSS the light speed barrier. So ‘things’ that DO go faster than light, simply can’t go any SLOWER than the speed of light (think tachyons).

        1. Reminds me of LeGuin’s “ansible”. Seems FTL communication will be an absolute necessity if/when we attain true space travel abilities.

        2. Those things have complex valued energy, you know. They don’t exist.

          Reversely, faster than light travel is likely impossible. It would mean (relative) time travel, which in turn means computers can be made to implode the computational tower of complexity. Which means everything is equally complex to solve, which is _not_ observed. (I’m paraphrasing CS Aaronson, who has a paper on arxiv on this.)

          He! Last I heard a physicist who said he had found that a wormhole ftl/time travel solution was possible, but then “the universe explodes”. It does too, ftl destabilizes the light cone of gauge theories (i.e. quantum field theories). Another arxiv paper.

          Those ideas are pipe dreams.

        1. “Shoot” is OK. Many of you must know the story about an American pilot who did an emergency landing on a North Korean air field during the Korean war. The Northern Koreans were of course excited to get their hands
          on a modern American jet, and an investigator climbed in the cockpit and asked the American pilot about the controls, such as the altimeter, speedometer, etc. Then there was this red handle on the side of the dashboard. “What is that,” he asked the pilot. “I’m not telling you that,” the pilot replied. “Don’t worry,” said the investigator, and pulled the handle. Well, the unlucky investigator found out whether there is an afterlife or not in a few milliseconds, but unfortunately couldn’t tell anyone…

  6. Whenever a scientist at CalTech uses a term like ‘plonk,’ which is a cheap wine of, sometimes, barely drinkable quality, I wonder what he means… and smile having at least knowledge and significant experience with part of his discourse.

    1. My parents used to manufacture this.

      It was a lovely afternoon, and I was there visiting, and my mom said, “Marta, would you like a glass of wine?”

      I said I’d rather have beer, and then she said, “we don’t have any beer, but try a glass of this wine. We made it ourselves!” So I said, “sure, Mom”.

      So I sipped a tiny bit, and tears formed and my mouth suckered in like I’d left my teeth out. I said, say Mom, what do you call this stuff? And she said, “well, we call it ‘plonk'”.

      Good memory.

      1. LOL! I live in the Napa Valley and have never heard of this “plonk”. I guess “Two-Buck-Chuck” (Charles Shaw)would count as plonk.

    1. I just noticed that the article includes authors from University of Tromsø where I studied for a year as well as the Institute of Ophthalmology where I worked in the library!

    2. that is so cool! i wonder if they are the only mammals to see in the ultraviolet range?

  8. That Guardian article’s a bit wrong, one should include the expansion of space to calculate the proper distance of objects that far away. That GRB occurred 13 billion years ago, 30 billion light years away. So, most of the way to the 46 billion light year limit of the observable universe. Cooler now, eh? 😉

    1. “That GRB occurred 13 billion years ago, 30 billion light years away. So, most of the way to the 46 billion light year limit of the observable universe.”

      You are right that it is near to the limit of the observable universe, but it wasn’t 30 billion light years when it happened. Such a thing would be way beyond the observable horizon.

      1. Yeah, I know, but that’s how far it is now. Sorry if I was unclear! I hadn’t seen Gavin’s comment above when I posted that, I guess it had been awhile since I refreshed the page. He put it better than I did: it is best to just talk about time and not distance when referring to things like this. That was along the lines of what I was trying to say there.

  9. ” … a very distant star—more than 13 billion light years away—has exploded violently. This is about a quarter of the distance between Earth and the edge of the observable universe, which is about 46 billion light years.”

    Actually Jerry, this event is/was very close to the edge of the observable universe. The confusion here is that the “13 billion light years” is the distance light from it has traveled to get to us. However, during that time that star’s neighborhood has moved (owing to the expansion of the universe) much further away, and is now near 46 billion light years away.

    Of course we can’t see it where it is now (owing to finite light travel speed), we can only see this “edge of the observable universe” as it was 13.7 billion years ago, when it was a lot closer.

      1. Not much, even the Swift home page managed to get that one wrong!

        The paper says a photometric redshift z ~ 9.4. (Since they don’t go into fancy stuff like “time” and “distance”.)

        Davis & Lineweaver places z = 10 at ~ 13 Gy ago and ~ 30 Glyr comoving distance. (Figure 1.)

    2. “Space is big. You just won’t believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it’s a long way down the road to the chemist’s, but that’s just peanuts to space.”

      1. But you can “roll up” space. Just think of the roll of kitchen aluminum foil. On the box it says 50 meter, but you can fit it in your kitchen drawer. If you aren’t convinced, just ask a theologian.

    3. well he DID say “more than 13 billion light years away”. 13 billion, 46 billion – who’s counting? 😛

      Really, though – thanks for the explanation.

      1. Technically correct- The best KIND of correct!

        (Spacey talk always brings the obscure Futurama references out of me.)

  10. Just a note on the metric expansion of space, since there seems to be some confusion about what it means.

    First, it does not just apply to the hypothetical period of Inflation. It applies to the era that began after inflation, a fraction of a second after the beginning of the universe, all the way until the present day. For this era, all observations of the universe have been consistent with a solution to Einstein’s field equations of General Relativity (GR), known as the “FLRW metric”.

    Space does not expand “into” anything. It is the space itself that expands under this model, in other words the distances between objects increases. This is impossible to visualize. A one-dimensional analogy may help:

    Imagine an infinitely long rubber band, on which an infinite number of ants are standing 6 inches apart. If the rubber band stretches, you can see that the ants become further apart, whilst locally they are not moving. The tricky part to conceive is that the rubber band was infinitely long at the beginning, and after stretching it is still infinitely long, although any two points on it are farther apart. Talking about the “overall length” of the rubber band increasing is meaningless, since it does not have a finite total length to measure. The ant analogy also makes it easy to see that the universe does not have a “centre” around which expansion is occuring. Things looks the same to any ant – everything is moving away, and more distant objects are moving away faster.

    It is not clear what the expansion of space “really” means. It’s not that space is really made from something that is stretching! It’s just that observations of distant objects all show that they are moving apart, following the rules of our expanding universe model, the FLRW metric.

    Two final points:
    (1) The further apart two objects are, the faster their speed of recession. This recession can exceed the speed of light, which is not a constraint under General Relativity. The speed limit only applies to “local” motion, so two objects can never move past each other faster that the speed of light.

    (2) The metric expansion of space only applies to distantly separated objects. It does not apply to gravitationally bound objects, usually local clusters of galaxies. So, for example, you won’t eventually become 7 feet tall, unless you are a 6’11” teenager. In fact, if the expansion continues for long enough, all we will eventually be able to see is the Milky Way and the few other galaxies in our “Local Group”.

    2. I like the 2D analog of space being the surface of a balloon- it’s got that finite but unbounded thing goin for it, forgoing the tricky bit about the infinitely long rubber band.

      1. I’m not a fan of the balloon analogy. For it to be applicable, we must imagine that the 2D surface of the balloon is all that exists. This is not intuitive. We can’t help but feel that the balloon is expanding “into” the 3rd dimension. Also, the surface of the balloon is finite. The universe is probably infinite, and I don’t think it helps to shy away from this issue.

        When thinking about going backwards in time toward the big bang, people intuitively imagine something with a finite diameter shrinking down to a point, where some kind of explosion occurred. The balloon analogy unfortunately reinforces this misconception.
        It is true that our observable universe is a sphere centered on us, and that it shrinks in size going back to the big bang, and expands going forward. However, most people wrongly imagine this as a sphere expanding or contracting in preexisting 3D space outside the sphere.

        Although we can probably never know what is beyond our own observable universe, we can assume that we are not so special that what we can see is all there is. And evidence about the curvature of space suggests that if the same laws apply to regions beyond what we can see, then the universe is indeed infinite. I think it’s important to get to grips with this inifity conceptually.

        As we go back in time toward the big bang, distances between objects decrease, and therefore the diameter of our observable universe shrinks toward a specific point centered on our current position. However, there is nothing special about this point. This is NOT the “location” of the big bang. If the universe is infinite, then at all times in the past it was infinite – and even just after the big bang when our observable universe was a tiny sphere nanometers in diameter, the universe still extended infinitely beyond it. And the big bang happened EVERYWHERE in this infinite universe.

        1. For some reason it’s always been pretty easy for me to understand that the Big Bang was not the event of a speck exploding “into” a space. However, this confused me:

          “This is NOT the “location” of the big bang. If the universe is infinite, then at all times in the past it was infinite – and even just after the big bang when our observable universe was a tiny sphere nanometers in diameter, the universe still extended infinitely beyond it. And the big bang happened EVERYWHERE in this infinite universe.”

          What exactly could be beyond the tiny sphere? Or are you saying the very properties of the universe at that size rendered it infinite? Hrm…I don’t think I’m asking this correctly but I just can’t think of another way.

          Also, by declaring this universe as infinite, does that rule out the possibility of multiple universes existing more or less at the same “time”? Forgive my…simpleness…but this really is so very interesting to me!

          1. The sphere that represents our observable universe is not the entire universe. It is not an “edge”, it’s just the furthest that we can see from our own arbitrary position. An observer in another galaxy will have a different observable universe, the sphere of which may or may not overlap our own, but will certainly extend to some degree into a region of the universe that we can never see.

            Going back in time to the big bang, the observable universe for each observer is a different sphere centered on his own location in space. The spheres all shrink in diameter, and their centers all get closer together. But if there are infinitely many of them, however much you shrink the scale of the universe, its extent remains infinite.

            To confuse matters, although the prevailing view is that the universe is infinite, it is possible under the FLRW metric (General Relativity) to have a finite universe. It is also possible for the entire finite universe to be smaller than the observable universe! In that case, light has time to traverse the entire universe more than once. The GRB might have happened exactly where we are now 13 billion years ago, and the photons traversed the entire universe and got back to the same place for us to see them now.

          2. The more you learn, the more questions there are! LOL…thanks again for your responses – I don’t quite understand but will continue to learn what I can. I often look for kid’s websites to help me comprehend some of this.

    3. In fact, if the expansion continues for long enough, all we will eventually be able to see is the Milky Way and the few other galaxies in our “Local Group”.

      Which raises some interesting questions about what observers (if ny!) might then think about the universe, esp. if information now known is lost.

      http://www.nytimes.com/2011/01/16/opinion/16greene.html

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