Slashdot Mirror

← Back to Stories (view on slashdot.org)

The Star That Exploded At the Dawn of Time

Posted by samzenpus on from the in-the-beginning dept.

sciencehabit writes To probe the dawn of time, astronomers usually peer far away; but now they've made a notable discovery close to home. An ancient star a mere thousand light-years from Earth bears chemical elements that may have been forged by the death of a star that was both extremely massive and one of the first to arise after the big bang. If confirmed, the finding means that some of the universe's first stars were so massive they died in exceptionally violent explosions that altered the growth of early galaxies.

55 comments

  1. Why can't hydrogen cool? by ShanghaiBill · · Score: 3, Interesting

    From TFA:

    The big bang produced only hydrogen, helium, and a little lithium, and gas clouds containing only these elements can't cool.

    Can someone please explain this? What would prevent a cloud of primordial elements from cooling?

    1. Re:Why can't hydrogen cool? by __aanbvm4272 · · Score: 1

      It burns and can't condense(cool?)

    2. Re:Why can't hydrogen cool? by tysonedwards · · Score: 4, Informative

      It's deceptive. At this point in time, the universe was quite small relatively speaking. As such, the density of those materials was still sufficiently high that the materials were in a persistent plasma state even though they weren't a "star", however fusion was still taking place converting Hydrogen to Helium. At this point, we're talking about all matter in the Universe occupying something not much larger than the Milky Way after all, maybe a little larger considering that we're talking about very, very fast expansion of the universe and the difference of a second amounts to a light year or so of growth. As the Universe continued to expand outwards and the material became less dense, it allowed for the material to actually split apart from one giant clump of hydrogen, helium and lithium and begin to actually get some empty space. As that empty space formed, then this plasmatic cloud could coalesce into the first stars. As long as there was these plasma clouds and not "empty space", then yes, there was "nothing" yet in which the material could *cool* into.

      --
      Thirty four characters live here.
    3. Re: Why can't hydrogen cool? by Anonymous Coward · · Score: 0

      I am not an astronomer.

      The wording in this article seems really odd to me. The science also sounds dubious at best.

      Any matter in the universe should cool down and not require heavier elements to do so.

      It's possible that this article was trying to talk about the very early universe when things were still really hot and hadn't had much time (relatively speaking of course) to actually cool off.

    4. Re:Why can't hydrogen cool? by Anonymous Coward · · Score: 0

      gravitational attraction, condensation and the eventual ignition of fusion all generate heat in these clouds.
      not to mention that the universe was really REALLY fuckin hot for millions of years after the big bang, so it is technically correct, if awkwardly phrased.

    5. Re:Why can't hydrogen cool? by ShanghaiBill · · Score: 5, Informative

      I appreciate your explanation, but honestly, what you say makes no sense. To be blunt, I don't think you know what you are talking about. You say that the Universe was the size of the Milky Way, and expanding by a light year per second. Since the Milky Way is only 120,000 light years across, if the Universe was really expanding that quickly, it would be bigger than the Milky Way in ONE DAY. You also say that hydrogen fusion was occurring, but according to this graph, fusion stopped three minutes after the big bang. There is nothing that you say that would only apply to H-He-Li and would not apply to heavier elements.

      I found the following explanation here:

      Hydrogen and helium are, by far, the most abundant elements in interstellar clouds. However, these elements are very poor coolants because they cannot be collisionally induced to emit photons at the low gas temperatures characteristic of molecular clouds. Two decades of theoretical studies have consistently predicted that a large fraction of the total cooling is borne by a few other atoms and molecules, notably gaseous water (HO), carbon monoxide (CO), molecular oxygen (O), and atomic carbon (C).

    6. Re:Why can't hydrogen cool? by mmell · · Score: 3, Interesting

      It can - now. Back then, where would the heat go . . . out of the Universe?

    7. Re:Why can't hydrogen cool? by mmell · · Score: 1
      I know that hyperexpansion is the most widely accepted theory these days to account for our observations of the Universe's size, density and composition, but it is not universally accepted and (for obvious reasons) not proven - at least not yet.

      I personally have doubts. After all, we can't observe the "edge" of the Universe now, only where the "edge" was some fourteen billion years ago. That "light cone" problem also sorta puts a damper on how detailed an observation we can make. Not saying it's a bad theory, just that I'm having a hard time seeing how it's falsifiable. Besides, everyone knows it's turtles all the way down . . .

    8. Re: Why can't hydrogen cool? by Anonymous Coward · · Score: 0

      also at this early time isnkt the matter vs antimatter effect being overlooked?

    9. Re:Why can't hydrogen cool? by Anonymous Coward · · Score: 0

      That's a bit obtuse. Unless someone or other opened a window the heat still cannot escape from the universe.

    10. Re:Why can't hydrogen cool? by stevelinton · · Score: 2

      Basically the conditions (temperature, density, amount of ionizing radiation around) thought to apply, the gas would be made up of atoms that tend to simply bounce off one another when they collide. This doesn't change the total energy in random motion of the cloud, ie the temperature.

      More complex atoms or molecules can interact in more complicated ways when they collide, so that part of the energy ends up as vibration in a molecule, or extra energy of an electron in an excited state. These vibrating molecules or excited atoms then relax back to their ground state releasing a photon and so actually cooling the cloud.

    11. Re:Why can't hydrogen cool? by mdsolar · · Score: 1

      You've got this right. Rotational transitions are the important ones (aside from atomic carbon). For molecular hydrogen, these are at higher energy so the most abundant molecule does not contribute much to radiative cooling normally. It does become important in primordial gas, but then the gas has to be warmer to excite those transitions.

    12. Re:Why can't hydrogen cool? by mdsolar · · Score: 2

      The universe cools as it expands. Once the background radiation is cool enough then the heat of contraction can dissipate. Initially, growth of structure in the universe happens only in dark matter because the normal matter smooths out destiny fluctuations. But after recombination, the normal matter begins to catch up. http://books.google.com/books?...

    13. Re: Why can't hydrogen cool? by mdsolar · · Score: 1

      No, that was happening much earlier. Antimatter in the form of positrons is important in the pair instability though.

    14. Re:Why can't hydrogen cool? by bigsexyjoe · · Score: 1

      The article doesn't say they couldn't cool in the conditions of the early universe, it says such a cloud could never cool.

      I'm not a chemist, but I would guess it's because the electrons cannot fall to a lower energy state, which converts heat to radiation. Since the heat is not radiated, it stays heat inside the cloud.

      Or the article gets the details wrong...

      --
      Democracy Now! - your daily, uncensored, corporate-free
    15. Re:Why can't hydrogen cool? by mmell · · Score: 1

      Congratulations on demonstrating an understanding of the first law of thermodynamics.

    16. Re:Why can't hydrogen cool? by mmell · · Score: 1

      Technically - the local temperature drops, the Universe has as much "heat" now as it had in the instant after the big bang. A lot of that energy is presumably tied up in the quantum foam, but none of that heat has left the Universe - unless the Universe has sprung a leak.

    17. Re:Why can't hydrogen cool? by Vitriol+Angst · · Score: 1

      To explain this, not only will the Higgs Boson be created to explain away the aether, and Dark Matter to explain why there's more gravity at a distance than up close, but now we need learn that particles cannot cool unless they are affected by the "Snoop Dog" field.

      --
      >>"ad space available -- low rates!!!"
    18. Re:Why can't hydrogen cool? by Vitriol+Angst · · Score: 1

      Where does the heat go NOW? It's a closed system (as far as we know).

      Heat is energy, and it's either going into matter or more energy. So it becomes more Complex.

      However, we have more Space -- so it's better to say that "heat has diffused, or become a more complex interaction." For instance, if all force at one time went in one direction, it "seems" like there is less energy if there is equal and opposing force. Also, is all particles in a system are headed in one direction - they still have force, but the energy seems to "be at rest" relative to that system. At least if we keep things in a Newtonian Universe.

      I think however, that much of the energy has "sublimated" -- or is at a frequency we don't interact with. Like what is called quantum fluctuations or "vacuum energy". The "cold matter" we interact with, has a much lower frequency and so rides on top of a lot of the energy (like a carrier wave) that existed from the Big Bang. Not sure if that is accepted theory, but it's the obvious answer that springs to mind if I'm sticking with a General Relativity Universe.

      To think about it is kind of awesome; right now, there is as much energy and activity as when the Universe first "exploded" into existence -- however, I theorize we have a 12 dimensional Universe, so a lot of the energy is being traded to a subset of 4 dimensions while we "appear" to have more empty space. The side effect of this interaction produces what we call gravity. However, that's just my theory, but it seems more simple than the other models. ;-)

      --
      >>"ad space available -- low rates!!!"
    19. Re:Why can't hydrogen cool? by HiThere · · Score: 1

      Well, that's the current theory, but I still have trouble accepting dark matter. Perhaps they'll actually find some soon. It *does* fit with the math, so it's easy to understand why it's been proposed and believed in, but "believed in" feels more appropriate for religion than for science. I'll grant that it's the best current theory, but until they actually catch some, or explain why they can't in a convincing way, I'm going to remain iffy about it.

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
    20. Re:Why can't hydrogen cool? by HiThere · · Score: 1

      You're being silly. There are good reasons that the clouds of hydrogen couldn't (easily) cool, and they remain true today. Of course these days the clouds are "polluted" with various heavy elements which radiate well and allow the clouds to cool relatively easily. (Even under current condition radiative cooling is rather inefficient.) Hydrogen just has a hard time radiating. It can, a little bit, but not very well. If the cloud is too hot, there aren't any bound electrons, so you don't even get the current (poor) radiation that hydrogen can provide, because radiative cooling depends on an electron slipping from an excited state to a non-excited state, and emitting a photon in the process.

      I trust you don't want me to go on.

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
    21. Re:Why can't hydrogen cool? by Anonymous Coward · · Score: 1

      In order for a particle to cool it either needs to collide with another particle, which is cooler, so that it can transfer kinetic energy to it, or it needs to have electrons in unstable (high energy) orbits so that it can release photons when the electron returns to a lower energy state. Back in those days the molecular hydrogen was really hot, so hot it couldn't even hold on to it's electrons (a plasma) and collisions with other hydrogen atoms would not have reduced the kinetic energy of those atoms, so the temperature of the cloud remains unchanged. Increasing the volume of the cloud would cause cooling but gravity was trying to do exactly the opposite.

      As the article points out, it takes a whopping big cloud of hydrogen plasma for it's gravity to overcome it's outward pressure due to temperature.

    22. Re:Why can't hydrogen cool? by david_thornley · · Score: 1

      I don't understand,. I have no difficulty in believing there might be something like slow, heavy, neutrinos. If I didn't know about neutrinos, dark matter would sound more dubious.

      --
      "When you have eliminated the unacceptable, whatever is left, however improbable, must be the truthiness" - Holmes
    23. Re:Why can't hydrogen cool? by mdsolar · · Score: 1

      I think you might enjoy this paradox: http://en.wikipedia.org/wiki/O...

    24. Re:Why can't hydrogen cool? by HiThere · · Score: 1

      If they find "slow, heavy, neutrinos", then I'll believe them. Now I just think it makes sense to look.

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
  2. Population II stars and globular star clusters by torsmo · · Score: 2

    Why are they present mostly in the galactic halo? Also, stars like SM0313 are supposed to have formed only a 100mn or so years after the Big Bang. Is that enough time for Population III stars to have formed and gone supernova?

    1. Re:Population II stars and globular star clusters by mmell · · Score: 1

      Something to do with how galaxies form?

    2. Re:Population II stars and globular star clusters by mdsolar · · Score: 1

      The question is more why are Population I stars mostly in the disk. The answer is that the disk formed later. The main sequence lifetime of massive stars is about a million years so there is not big timing issue related to that. http://en.wikipedia.org/wiki/M...

  3. I took this for granted by Anonymous Coward · · Score: 2, Interesting

    Big Bang -> a few ridiculously massive stars -> a few little Bangs -> many massive stars -> many hypernovae -> many many large stars -> many many supernovae -> ... -> ... -> Michael Bay

    It's explosions all the way down.

  4. All the gold by invictusvoyd · · Score: 1

    Is ancient ! .. All that gold !!!

  5. It's called "theory" for a reason by osiaq · · Score: 0

    It's called "theory" for a reason

    1. Re:It's called "theory" for a reason by cupantae · · Score: 1

      It's called "theory" for a reason

      Because that's the word that has come to represent the meaning of the word "theory"?
      I'm sorry, I can't work out what point you're trying to make.

      --
      --
    2. Re:It's called "theory" for a reason by Bob_Who · · Score: 1

      It's called "theory" for a reason

      Because that's the word that has come to represent the meaning of the word "theory"? I'm sorry, I can't work out what point you're trying to make.

      I think it might be circular logic, which might suggest a closed universe (and reruns).

      Its like deja vu all over again.

      I just want to bang, bang, bang!

    3. Re:It's called "theory" for a reason by HiThere · · Score: 1

      He's probably expecting that if we were sure about it we'd call it a law. He's ignoring the game-rule of science that says you should never be sure anything is correct. All you can do is prove things wrong. And if there's no way to test whether it's wrong it's meaningless. (This is not the same as, and does not imply, "if there's no additional way to test whether it's wrong it's meaningless.")

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
    4. Re:It's called "theory" for a reason by cupantae · · Score: 1

      Yeah, but without even referencing the theory that's supposedly conjecture.
      What lazy idiocy.

      --
      --
  6. Pair-instability Supernovae by Rich0 · · Score: 2

    So, I don't get why pair-instability supernovae happen in the first place, and the Wikipedia article certainly isn't helping.

    The argument is that at some point a star gets hot enough that its photons start creating electron/positron pairs, and this causes a collapse. Then that collapse leads to a runaway nuclear reaction.

    What I don't get is how the star would ever become supercritical from a nuclear reaction perspective. I get that there might be some kind of transition in pair creation as the whole star gradually increases in temperature and perhaps a large portion of the star crosses some threshold temperature at the same time. I get that this could reduce pressure in the star and allow it to start collapsing.

    However, while the transition in pair-creation behavior might happen quickly (this is an event at the quantum level), the collapse of the star involves huge masses of gas falling inwards at macroscopic speeds. I don't see how the migration of a few dozen sun's worth of H/He towards the core is going to happen at a rate anywhere near the rate at which individual H/He atoms are colliding throughout the core. So, if the density started to rise such that you got an increase in nuclear reactions, wouldn't that create additional pressure that stops the collapse?

    For there to be an explosion you need to build up potential energy of some kind and then release it all at once. If you light C4 with a match it just burns from the surface which doesn't lead to a dramatic release of energy. If you send a shockwave through it that travels faster than the speed of sound in the medium then the initiation of combustion of the C4 propagates faster than the shock wave produced by the combustion, and as a result the energy of the entire explosive is released seemingly at once. Likewise if you ignite a cloud of pure hydrogen surrounded by normal air it will just burn at the surface hotly, but if you premix hydrogen and air to a stoichiometric mix and light a match, it will detonate, because in that case the ignition will naturally propagate faster than the speed of sound (and is not limited by the diffusion of oxygen/hydrogen to allow mixture).

    Nuclear reactors don't explode, because they aren't significantly supercritical - they stay near equilibrium. A nuclear bomb reaches supercriticality because for a very short moment in time the inertial of the collapsing fissile mass allows it to continue to collapse before the energy produced by the initiating chain reaction can blow it apart.

    Is that the case for these supernovae? Does it take long enough for the nuclear reactions to start that the mass of the falling gas has enough inertia to allow it to continue to compress even after passing the critical point?

    1. Re:Pair-instability Supernovae by mdsolar · · Score: 2

      This may help: http://articles.adsabs.harvard...

    2. Re:Pair-instability Supernovae by Anonymous Coward · · Score: 0

      I think you've got it: after pair-creation suddenly decreases the pressure, the outer layers of gas acquire considerable momentum, falling in towards the centre of the star, before the fusion rate starts dramatically increasing. That momentum keeps the core compressed long enough for fusion to release a lot of energy, before that energy eventually reverses the momentum and blows the outer layers of the star away.

      The article that another replier linked seems to mostly take this implicitly rather than stating it outright, but the following passage makes it fairly clear:

      More massive stars with higher entropies become unstable at lower temperatures. During the collapse they acquire a greater inward momentum, and reach a higher temperature at the reversal of collapse. There is a greater energy release from the oxygen burning, and so the explosion following the collapse is of greater intensity.

      (In this case, "oxygen burning" means the nuclear reaction that occurs is oxygen-oxygen fusion.)

      As you pointed out, this is analogous to what happens in a nuclear bomb: the inward momentum of the fissile material (and sometimes also a heavy "tamper" designed for this purpose), driven in this case by explosives rather than by gravity, keeps the fissile material confined long enough for a lot of fission to take place.

  7. Pair Instability Super Novae by mdsolar · · Score: 2

    The instability that causes the collapse of a stellar core and subsequent explosion comes from turning gamma rays into pairs of electrons and positrons. This turns energy into matter and cuts the pressure that the energy provides. http://en.wikipedia.org/wiki/P... It turns out that these explosions may make observing the early universe easier. One of the most important abundance ratios is the interstellar medium is the ratio of oxygen to carbon. The strength of the carbon monoxide bond is so strong that these two really pair up. Whichever runs out first determines the remaining chemistry to a large degree. Mass losing carbon rich stars produce carbon rich dust, while mass losing oxygen rich stars produce silicate dust for example. But, primordial Pair Instability Super Novae may produce lots of oxygen with little carbon or silicon to combine with. So the very early solid phase of the ISM may be mostly water ice. This happens to increase the far infrared emissivity of this solid phase making early objects brighter in the red-shifted sub-millimeter. Thus very early object may be easy to find in surveys at that wavelength. http://iopscience.iop.org/0004...

  8. "expanding by a light year per second" by mrops · · Score: 1

    Further how is this possible, if the speed of light is absolute... well you can't move matter more than 1 light second in one second and that too requires infinite enregy, no?

    1. Re:"expanding by a light year per second" by Anonymous Coward · · Score: 1

      Matter wasn't moving that fast; space itself was expanding that fast.

    2. Re:"expanding by a light year per second" by ShanghaiBill · · Score: 1

      Matter wasn't moving that fast; space itself was expanding that fast.

      Except that the super luminal inflation of space was over 1e-32 seconds after the big bang. I doubt if many stars were forming in that trillionth of a trillionth of a billionth of a second.

    3. Re:"expanding by a light year per second" by HiThere · · Score: 2

      You sure about that? I was under the impression that it was probably STILL expanding faster than light, if measured from edge to edge (which, of course, you can't do, but can only calculate). In fact I was under the impression that it was believed that many areas of the universe may still be rapidly inflating, just not around here.

      FWIW, (and in my understanding) there are theoretical reasons to believe that inflation will continue forever. They're just beyond our light cone. Perhaps this "problem" has been generally agreed to be resolved, but if so I haven't heard about it.

      OTOH, I am not a cosmologist.

      --

      I think we've pushed this "anyone can grow up to be president" thing too far.
  9. I got you one better, Mr. Fancy Pants Ancient Star by Anonymous Coward · · Score: 0

    The atoms that make up my body were created in the Big Bang itself, and half of them, statistically, were once antimatter.

  10. Best Title by Anonymous Coward · · Score: 0

    This is the best title of a Slashdot news story to be repurposed as the title of a rock song.

  11. Block Holes? by MrL0G1C · · Score: 1

    I thought 'extremely massive' stars were supposed to end up as black holes when they collapsed?

    --
    Waterfox - a Firefox fork with legacy extension support, security updates and better privacy by default.
    1. Re:Block Holes? by mdsolar · · Score: 1

      At low metalicity there is a range of stellar mass where the star is completely disrupted. Look at slide 36 here: http://www.mpa-garching.mpg.de...

    2. Re:Block Holes? by mmell · · Score: 1

      No, a lot of them just end up on the talk show circuit.

  12. Re:I got you one better, Mr. Fancy Pants Ancient S by mmell · · Score: 1
    Not quite. If yon atom is heavier than lithium, it's a fair bet it wasn't created until well after the big bang.

    Now, the quarks making up those newfangled heavy atoms - those have been around since the beginning.