Follow Slashdot stories on Twitter

 


Forgot your password?
Close
typodupeerror
×
Space Science

Quark Stars 243

Posted by michael from the stranger-than-we-can-imagine dept.
BigGar' writes "Astronomers seem to have discovered a new type of star. It would lie between a neutron star and and a black hole in the hierarchy of stars and consist of quark matter. Further observations with the Chandra X-ray telescope will be needed to confirm the results."
This discussion has been archived. No new comments can be posted.

Quark Stars More

Quark Stars

Comments Filter:

  • How does this fit in with String theory? (Score:3, Insightful)

    by Eryq ( 313869 ) on Thursday April 11, 2002 @12:45AM (#3321476) Homepage
    I had read once that black holes could be regarded as super-large elementary particles (described by very few parameters: spin, charge, mass). Would "quarks stars" be something like that, or more like a huge Bose-Einstein condensate?

    Jes curious....
    • Forgive me if I'm wrong, but I believe a neutron star isn't one large anything, it's a collection of neutrons, much like any normal matter is a collection of whole atoms. I believe the quark star they're talking about is supposedly another bundle of sub-atomic particles. A singularity supposedly has no size, therefore everything must be superimposed: ie, it's one thing. A Bose-thingimagic is a bunch of things which act like one at a very low temperature, I believe. This isn't either of those two, but an object with size and probably more than one component.
      • The difference, of course, is the mass and possibly density of a neutron star compared to that of an actual neuron.

        Its difficult to call a neutron star a collection of neutrons because in a normal neutron is composed of a (theoretically) fixed collection of quarks which "belong" to that neuron in some way; we have no such guarantee within a neuron star - in fact, its quite likely that all of the quarks composing a neutron star interact with each other in a way that is characteristic of the interactions of quarks within a single neutron.

        We think of neutrons as little "balls" of quantum probability which exhibit matter properties, but what if we "melted" those balls so that the surface of an object composed of such balls looked more like the (macroscale) ocean than a McDonald's playground ballpit?
    • First off, I don't have an astrophysics degree..yet ;)

      If someone were to refer to a black-hole as an elementary particle, imho it is because the tidal forces (the difference in the force of gravity felt between the two ends of a particle) are great enough to literally rip any individual atom within the BH apart - down to its fundamental level - a BH doesn't consist of protons or quarks, just mass located at a singularity. Of course it's been shown that Black Holes can carry a charge, as well as spin, but that is ostensibly independant of the behavior of the black hole as a single point vs say an active star.

      It would be more correct imho to think of a "Quark" star along the same lines of a Neutron Star or a White Dwarf (a White Dwarf is supported against gravity via "electron degeneracy pressure"). If this discovery holds, in order of increasing mass:

      White Dwarf, Neutron Star, "Quark" Star, Black Hole.

      Obligatory Karma Whore Link: http://cosmos.colorado.edu/astr1120/hypertext.html [colorado.edu]
    • I had read once that black holes could be regarded as super-large elementary particles

      Actually it's that statement you just made that doesn't fit with String theory. String theory predicts that black holes can retain information about the structure of objects that are sucked into them. If this turns out to be true, then they can't be regarded as large elementary particles, since elementary particles must be indistinguishable from each other.
      • You're talking about black holes preserving entropy, right?

        If we assume that ST is accurate, then I *think* the theory I heard was that a black hole made by collapsing a total of n strings would behave like a point in space containing a *single* string with a LOT of energy...

        But it sounds like you're saying that it would really behave more like a point in space where there were still n strings... and thus sufficient complexity to account for the information in the original objects.

        Do I have that right?

        • And a 4th dimension (Score:2, Interesting)

          by trezor ( 555230 )

          Physicians say they can't account for all the enrgy and mass that are beeing sucked into a black hole. As one of the elementary laws of physics is that the mass/energy of the universe is constant, this is a rather interesting remark.

          It would mean that the remained of this energy goes off to somewhere else. Where? Noby knows.

          But if this string theory implies that a black hole can memorize the structures of what is beeing drawn into it, that would make all that sci-fi black-hole/worm-hole multidimensional-travel things alot more real. At least in theory.

          Because if mass and energy disappears it has to appear somewhere else. And the only way it can go somewhere else, is by using dimensions unkown to us.

          I know this sounds spaced out beyond belief, but I like to keep my mind open for new things. If they're scientific enough :)

          Could anyone actually knowing anything about string-theory comment this?

          • Physicians say they can't account for all the enrgy and mass that are beeing sucked into a black hole.

            Strangely enough, neither can dentists or optometrists.

          • Physicians say they can't account for all the enrgy and mass that are beeing sucked into a black hole.

            Perhaps not, but physicists can. Because a black hole exhibits gravitational effects, you know that the mass and energy it contains are still there. Also, given time, a black hole will radiate energy away in what's dubbed Hawking radiation, and eventually burst in a radid outflow of this radiation, returning the energy to the universe for more diverse purposes.
      • Blockquoth the poster:

        If this turns out to be true, then they can't be regarded as large elementary particles, since elementary particles must be indistinguishable from each other...

        ... unless, of course, the string is vibrating in a complicated mixture of nodes, which is (I think) what the extremal black hole theory claims. Of course that relies on a belief that extremal black hole theory "explains" astronomical black holes, a belief that I cannot share. (Sorry, Amanda :) )

  • Analogies (Score:4, Funny)

    by tcd004 ( 134130 ) on Thursday April 11, 2002 @12:47AM (#3321482) Homepage
    "Neutron stars are the vestiges of immense supernova explosions, collapsed stars with extremely compact cores, denser than all known objects except black holes. A teaspoonful of a neutron star would weigh one billion tons, as much as all the cars and trucks on Earth."

    That would be one impressive teaspoon.

    Tall, Blonde and Weaponized [lostbrain.com]
    tcd004

    • Is it just me, or does anyone else find it odd that the densities of unusual astrophysical bodies are always measured in tons per teaspoon? The same way that the de facto measurement of storage is the Library of Congress (ie, this new optical disc can hold 300 Libraries of Congress!!) or "encyclopedias" (the Encyclopedia Britannica, I presume, and not Worldbook)? Bah. News writers.
      • Actually you've fallen out of date.
        This [cray.com] story, as referenced to Here [slashdot.org] starts using the Human Genome as a standard...

        The Library of Congress just isn't big enough anymore. The question is, do we need more books? or less genes?

    • Re:Analogies (Score:4, Funny)

      by Alsee ( 515537 ) on Thursday April 11, 2002 @02:42AM (#3321763) Homepage
      That would be one impressive teaspoon.

      There is no spoon.

      -
    • Spooooooooooooooooooon!!!!!!

      [c'mon, somebody *had* to say it.]

  • "Up" quarks and "down" quarks. (Score:3, Interesting)

    by Renraku ( 518261 ) on Thursday April 11, 2002 @12:48AM (#3321484) Homepage
    Does anyone know if all up quarks are the same as all other up quarks and if all down quarks are the same as all other down quarks? There might be a billion different slight variations of the two kinds. We don't have the equipment to define a quark past a certain level.

    • I'll say it with a song (Score:2, Funny)

      by Anonymous Coward
      An All-Linux Think Tank [monolinux.com]
      -----
      Quark Sing-a-long Written by Lynda Williams
      For Jefferson National Lab
      Bring Our Daughters to Work Day.
      (refrain)

      Up, Down, Charm, Strange, Top and Bottom!
      The World is made up of Quarks and Leptons!
      Up, Down, Charm, Strange,Top and Bottom!
      Yum! Yum!

      Quarks come in six flavors
      They live in families of two.
      Up Down, Charm Strange, Top and Bottom!
      They come in anti-flavors too!

      Each family makes a generation
      between which is a mass gap.
      The up quark is the lightest and the top quark
      is the most fat!

      The second and third generations
      do not live for very long.
      That's why everything in the Universe
      is made up of Ups and Downs!

      (refrain)

      Quarks carry a color charge.
      They come in red, green and blue.
      You'll never see a quark all by itself
      cuz they stick together with a strong force glue.

      Quarks carry electric charge.
      A fraction of electricity.
      Quarks combine together so the total charge
      is a multiple of unity!

      An up, up down makes a proton for a total charge of plus one.
      A down, up, down makes a DUD neutron!

      Physics is so much YUM YUM PHUN!

      (refrain)

      copyright 1999 Lynda Williams
      http://www.entersci.com/cosmic/quarkl.htm
    • Well, there are more than just up and down quarks, you know. There are also strange, charmed, top, and bottom quarks.

      I'm no string theory expert, but the impression I've gotten is that quark characteristics are prescribed by precise string oscillations, so until you can show otherwise, you should assume that all similarly flavored quarks are in fact the same.
    • Well, they can have different 'spin', so they are not all the same.
    • There are only a few properties used to describe subatomic particles, many of which have to do solely with its energy level, or position in an atomic shell or something. For example, every electron is exactly the same as every other electron, but there are 4 quantum numbers that describe it (l, m(l), m(s), and s). No two electrons can have the same set of quantum numbers in a single atom (or they would be the same electron), but of course you could have precisely the same quantum numbers in another atom. I am virtually certain that the same general principle applies to quarks. Their classification has nothing to do with the instruments we use to detect them, but rather with the parameters used to define them.

    • Re:"Up" quarks and "down" quarks. (Score:5, Informative)

      by zCyl ( 14362 ) on Thursday April 11, 2002 @01:18AM (#3321597)
      Does anyone know if all up quarks are the same as all other up quarks...

      Well the up quark, like any quark, is not as cleanly defined as the word "particle" might indicate. The up quark and the properties associated are not just a measure of how much "mass" or "spin" has been shoved into a sphere called the quark. The properties of quarks actually come from an extremely complex cloud of virtual particles that pop into and out of existence in close proximity to the area we call the quark. There seem to only be a few stable configurations of energy, spin, and charge that can result in a quark. The properties of the quarks seem to result from some intrinsic properties defining the way these virtual particles can interact, so you can't just put a little more of something into a quark, because that would require changing the rules of the interactions. Unfortunately, the precise details of all of the above is still a subject of some speculation, since no one quite knows for sure all the virtual particles that can pop in and out and all of their properties.

    • If they are the same, or even just similarly grouped, does that mean that physical existence is basically a binary system? I wouldn't be suprised, it's kinda everywhere: chinese philosophy (yin/yang, thing/no-thing), sex (male/female), life/death; I don't think it's any accident that binary worked out so well for computers.
    • Does anyone know if all up quarks are the same as all other up quarks and if all down quarks are the same as all other down quarks?

      Yup. I mean, there are a handful of "quantum numbers" like colour (three possible values) and spin (two possible values) that have been mentioned here (there might be other quantum numbers -- I forget offhand, and it depends on how you look at them anyway -- but there aren't many). But if two quarks have the same quantum numbers, they are indistinguishable. There are a lot of properties of matter that can be tested that depend on this indistinguishability, so we're pretty sure it's true; we don't have to see the quark itself very closely to know this (which is kind of cool, really).

      (Sort of like how we know there are exactly three possible quark colours: certain reactions, for example, are more or less likely depending on how many possible colours there are. Yay, indirect measurement!)

  • yeah, ok (Score:3, Funny)

    by doooras ( 543177 ) on Thursday April 11, 2002 @12:50AM (#3321496)
    I guess Armin Shimmerman was pretty cool, but I don't think he's really a star... Or was that a different kind of Quark, that doesn't try selling self-sealing stembolts...

  • Why can we see it? (Score:2, Insightful)

    by Anonymous Coward
    This stuff looks dense enough to be a black hole (black hole in the sense of "light can't get out", not necessarily "singularity"). So, what kind of densities do you need to get a blackhole, or does the total mass also enters the equation?

    • Re:Why can we see it? (Score:2, Interesting)

      by PhuCknuT ( 1703 )
      If it were dense enough that light couldn't escape, it would form a singularity too. Can't have one without the other, if it's high enough density to trap light, then there are no forces, even at the subatomic level, that can resist the collapse to a singularity. What they are talking about here is a stage that they didn't realize existed, where very dense neutron stars collapse one level further without becoming a black hole.
  • So why does Quark get a star type named after him.. Who'd he swindle that Deal from? :)

    • Re:Star Trek Deep Space Nine (Score:2, Interesting)

      by Anonymous Coward
      Erm, the word Quark comes from Finnegans Wake by James Joyce.

      From the Fourth Chapter of the Second Book:

      -- Three quarks for Muster Mark!
      Sure he hasn't got much of a bark
      And sure any he has it's all beside the mark.
      But O, Wreneagle Almighty, wouldn't un be a sky of a lark
      To see that old buzzard whooping about for uns shirt in the dark
      And he hunting round for uns speckled trousers around by Palmer- stown Park?
      Hohohoho, moulty Mark!
      You're the rummest old rooster ever flopped out of a Noah's ark
      And you think you're cock of the wark.
      Fowls, up! Tristy's the spry young spark
      That'll tread her and wed her and bed her and red her
      Without ever winking the tail of a feather
      And that's how that chap's going to make his money and mark!
      Overhoved, shrillgleescreaming. That song sang seaswans.
  • but, in that series, you just can't beat Dax in spandex!

  • I was just getting used to that, after the story on slashdot [slashdot.org]...

  • Quark Matter is Not New (Score:5, Insightful)

    by dragons_flight ( 515217 ) on Thursday April 11, 2002 @01:09AM (#3321569) Homepage
    Quark stars are a new and interesting idea, but quark matter in general is not a new idea. "Quark matter", more usually "quark plasma" or "quark-gluon plasma", is believed to be the dominant form of matter in the universe just following the big bang. There is also early evidence [web.cern.ch] that it's been witnessed in some of the largest particle accelerators.

    In normal matter quarks group together in sets of 3 to form protons and nuetrons. Rare particles, like pions, can be formed from pairs of quarks, but quarks never appear in isolation, for them it's always in groups of 2 or 3. In quark plasmas though there aren't any distinct groups of twos and threes. All the quarks are smushed into a single substance with arbitrarily large numbers of quarks.

    One analogy is if atoms are built out of "solid" quarks (in the from of protons and nuetrons), then the quark plasma is like melting them so they all run together. Prior to this announcement the only time that quark plasmas were expected to appear was in the presence of extraordinarily high energies and temperatures.

    We could predict that nuetrons stars should exist because the "nuetron degeneracy pressure" which makes them possible was well understood theoretically. The theory that governs quark interaction is known as quantum chromodynamics and is far more complicated. I'm not sure whether anyone knows how to apply it to massive collapsing stars, and it doesn't surprise me if no one ever tried. It will be interesting to see if the existing theory can be made to justify quark stars. If not, well that's when things really start to get exciting.

    • In normal matter quarks group together in sets of 3 to form protons and nuetrons. Rare particles, like pions, can be formed from pairs of quarks, but quarks never appear in isolation, for them it's always in groups of 2 or 3. In quark plasmas though there aren't any distinct groups of twos and threes.

      That's pretty close to the truth, but you missed one important detail.
      Pions (and other mesons) are made from a paired quark and antiquark, not two quarks.

      Baryons like protons and neutrons are made up of three quarks bound together by their color charges, so for example a proton is (I think) made of two up quarks and a down quark, where you have one quark each of red, green, and blue color charge. Mesons contain a quark and an antiquark of the opposite color (i.e. red and antired).

    • Quark stars are not a new idea either. The idea has been floating around for 20 years or more, and has been invoked to try to explain all sorts of cosmic events, gamma ray bursters, the Tunguska event, you name it. I've got a paper by Witten on this subject from the mid-80s.

      The basic idea behind strange quark matter is really easy to understand, and has very little to do with quantum chromodynamics, and everything to do with thermodynamics. If you have two kinds of fermion (up, down) and squeeze them together (gravity), they'll reach a certain energy state determined by Fermi-Dirac statistics - the Pauli exclusion principle. If you thrown in another type of fermion (strange), and apply the same pressure, you'll get more particles in the same space because there are now more states for the fermions to occupy without running into the Pauli exclusion principle. A strange quark can have exactly the same energy as an up as a down, because they are still different. There are now three quarks occupying a certain energy level instead of two.

      There are many very interesting implications of this which aren't mentioned in any article I've seen, including the possibility of exothermic reactions from such a ball of strange quark matter. That's sekrit code talk for something very exciting and far out which I won't mention explicitly because I'm not a crackpot. No, really! Witten and Fitch said it first anyway.

      The theory is there. Now it'll be interesting to see if we can make any of this stuff in an accelerator.

      Now let's see how this gets modded, since I'm the only person on /. who has ever published a paper in PRL on the subject of strange quark matter. I'm betting 2 at most.

  • Sounds cool... (Score:3, Funny)

    by Jugalator ( 259273 ) on Thursday April 11, 2002 @01:20AM (#3321602) Journal
    Or as Mr D. Vader would put it:

    If you only new the power of the quark side...

  • Is any of this real? (Score:2, Interesting)

    by ClubPetey ( 324486 )
    Ok, seriously, I'm not a physicist, but I did pay attention in High School/College, and I have to ask: Do we KNOW any of this stuff. Or is everything just one (educated) guess on top of another.

    Yes, we've made some discoveries, and for the most part things can be explained with the current line of thinking in Physics (Newton, Einstein, etc), but that's the problem, things are only MOSTLY explained, and certain keys are missing.

    Take Newton, we've got all sorts of formulas, rules, and experiements built upon the concept of gravity. Something which we cannot define, do not know how it is "made" nor where it comes from. Or perhaps think of the stars, do we KNOW that this star is 8 billion light-year away? Or are we just guessing based on some color-shifting theory that seems to work here on Earth, based on guesses about the total mass of the universe (that we can't find some large percentage of...)

    What if we humans are all WAY WAY wrong? What if like the "flat-earthers" of centuries ago, we've justified our THEORY of the planets, stars, solar systems, and the universe based on a completely incorrect model just becuase researchers (or humans in general) don't like to admit they are wrong, or that they don't know something? Are there any radical thinkers left? someone perhaps not starting from Newton or Einstein's work and trying to move it forward, but someone with NO preconsceptions, NO ingrained ideas, and NO outside influences?

    Actually, nevermind, even if a person like that did exist, he'd be labeled as a quack in the media, shunned and laughed at by acedemia and problably killed by a nervous government.

    Just some random thoughts on a quiet night...
    • You say, "Newton, Einstein, etc.", but think about the gap between those two theoretical branches. It's huge! Newton was completely unaware of the principles behind Einstein's work and based his model on nothing but observed phenomena, right? Of course, that doesn't mean that Newton is bunk, just that it's accurate for observed phenomena within a specific range. Einstein's range is much larger, including things that Newton couldn't possibly have measured to note discrepancies. One must assume that future discoveries will continue to provide larger and larger frames of reference, not supplant what we have. However, the change will be in our understanding of the boundary conditions, not of easily observed things. Heck, how are we doing research now? Particle accelerators! That ain't your everyday environment...
    • Something that one gets used to in science is that you don't know anything in the absolute sense, but you probably do "know" things to the degree that you're willing to base your life's work off of them. On the other hand, if you spend too much time around philosophers, you might end up wondering if the world really exists, or if your senses are accurate, etc.

      Doubt goes hand in hand with wisdom. Once one accepts that there is room to question absolutely everything, then you just have to accept the attitude of estimating what is the most likely truth and working from there. In my (admittedly biased) estimation the laws of physics, as currently understood, are almost certainly a good approximation of truth, though certainly not the last word.

      In science, careers are made by showing that the established beliefs are wrong. There are lots of people itching to overturn current theories. Sometimes there is resistance if the evidence is weak or the argument complicated, but in the long run scientists are often more likely to admit their mistaken beliefs than the public in general.

      If there really is a right answer to the universe then an independant thinker should arrive at similar conclusions to the ones we already have. Unfortunately no man ever born could even learn all the science we have now, so it's nigh impossible to believe that any single person could have the capacity to independantly arrive at more than a very small part of what has already become established doctrine. On the other hand, Ramanujan [wolfram.com] did quite well, and without being shunned or killed.

      If some day we do contact an intelligent alien race, that would be other best chance to study an independant notion of science. However, I doubt that they'll offer too many surprises among the areas of science that have been studied in detail.

    • Re:Is any of this real? (Score:5, Interesting)

      by gilroy ( 155262 ) on Thursday April 11, 2002 @02:32AM (#3321749) Homepage Journal
      Blockquoth the poster:

      Ok, seriously, I'm not a physicist, but I did pay attention in High School/College, and I have to ask: Do we KNOW any of this stuff. Or is everything just one (educated) guess on top of another.

      Well, there is no revealed truth in science, so we don't ever know absolutely that something is real. It has happened before that a theory turns out to be based on a house of cards. Most of that time, in retrospect, it can be seen that the theory got way out in front of experiment and so was improperly constrained. That is, the less we've studied an area, the more likely the theoriest are wrong. As facts come in, theories get revised or strengthened.


      On the other hand, remember that in physics, most "revolutions" change our understanding of how things work but do not invalidate existing theories in their realm of applicability. For example, relativity didn't kill Newtonian theory. Indeed, that's still where we start today in physics education. Why didn't it? Because at human-scale speeds, with human-scale masses, objects obey Newton's Law pretty well... that's the region in which the theory was derived and it fits the experiments there. At the very fast, it breaks down, and then relativity is needed.


      Now, we insist the Universe is "really" relativistic at all speeds, so in that sense the new theory wiped out the old. But we also insist that for slow objects relativity must reduce to Newton's Law (and it does). So the earlier theory reamins a useful, if admittedly inadequate, tool.

      • Exactly...relativity applies across all speeds and scales. So when I think that it took an hour to get to work, that's just in my frame of reference. In my boss's frame of reference, it took 1.0000000000001 hours and I'm late...
    • I did pay attention in High School/College, and I have to ask: Do we KNOW any of this stuff.

      Sure prevailing theories influence what we look for, the way we look for it (instrument design) and the questions we ask of our observations. But that does not mean that there might be no substance to the scientific concensus.

      One thing that is blindingly obvious from any perusal of the last couple of centuries of human history is that the rise of the scientific method has provided a potent tool to tamper with the world with.

      While I certainly don't claim any ability to turn off my knowledge of such theories when looking at the world, I do see them rendering many things sensible which without them would demand special explanation ... moreso given our propensity to ask and answer the Why? question even in circumstances where it should neither bn asked nor answered.

      The example I like best is the theory of plate tectonics which renders sensible a host of observations and phenomena, such as volcanos and earthquakes, and ultimately has been shown by increasingly accurate measurement to account for the observed relative movement of adjacent tectonic plates.

      When it comes to data from distant galaxies or from the subatomic realm, my confidence relies on little more than simple extrapolation from what I can observe directly with my own senses through the clear breadth gained by using even simple telescopes and microscopes to there being no sign of discontinuity as the power of such instruments is scaled up.

      Are there any radical thinkers left? someone perhaps not starting from Newton or Einstein's work and trying to move it forward, but someone with NO preconsceptions, NO ingrained ideas, and NO outside influences?

      Without language, it is going to be worse than hard for anybody to think too deeply in these areas, so it doesn't make any more sense to try to set up such a straw man than to try to ascertain the cosmology of an elephant.

      Yet it remains important to remind ourselves just how much evil has been perpetarated by those who believed they knew the authoritative truth.

      So how far can we go in discarding preconceptions and looking again with an open mind? And might anybody actually do it if they could?

      Here I can only go from personal experience, although an experience I suspect at least a few have shared. As an already mature adult, I reached a point where things clearly were not working the way I had long assumed they would, so I consciously put aside my preconceptions and tried to start from scratch to find out how the world really works.

      Now I'm first to admit it is nigh on impossible to put every detail behind you, most especially not deep personal values, likes and dislikes, but at least for me it was possible to have a sincerely fresh look at how the world works.

      And while I certainly didn't find something which would overturn the bulk of mainstream science, I did identify useful patterns that extend way beyond the then traditional scope of science ... knowledge that now gives me a pretty good idea when leading cosmologists might be typing with one hand.
    • We have justified our theories based on methods of reasoning we believe to be infallible (the laws of mathematics and logic) and results of observations which we know are imperfect but which are usually "close enough" to the theory. If anyone ever came out with a disproof of science that was falsifiable (there is a situation imaginable under which the proposal would clearly be false), reproducible, logical, and otherwise consistent, it would slowly but surrely become accepted. It took 1500 years but we did finally accept that the Earth was round and it revolved around the sun (at least, we accepted that those explanations are closer to observed phenomena than what came before).
    • Or perhaps think of the stars, do we KNOW that this star is 8 billion light-year away? Or are we just guessing based on some color-shifting theory that seems to work here on Earth...

      I'll just chime in here on the subject of stellar distances, based on my understanding as a (very) amateur astronomer (so if you know more than me, feel free to correct me wherever I make errors).

      Stellar distances as calculated by astronomers are based on less "exotic" ideas than the doppler effect. For nearby stars (less than 500 light years away or so), we can use parallax. As the Earth goes from one side of its orbit to the other, we can measure how far one of these nearby stars moves relative to the background stars. Closer stars will appear to move more than more distant ones (the same way roadside objects appear to move much more quickly than a tree or mountain in the background). So unless there is some bizzare undiscovered property of physics that causes parallax to not work in space, we can be pretty sure we have accurate distances for these nearby stars.

      Using that information, we can check our other measuring sticks used over longer distances. Main-sequence stars (normal stars such as our Sun and 90% of the stars in the sky) have a color which corresponds directly to their intrinsic brightness. The apparent brightness of a star (how bright it appears to us) is inversely proportional to its distance. So, knowing it's intrinsic brightness (based on color) and its apparent brightness (by looking at it), we can calculate its distance. We can calibrate this color->brightness function by examining nearby stars whose distance can be measured with parallax.

      Also, there is a special class of stars called Chepheid variable stars who vary in brightness on a regular period. The length of that period is a function of the intrinsic brightness of the star. Knowing that, and the apparent brightness, we can calculate the distance. Again, we can calibrate our function of period->brightness based on parallax. These stars are all over the place, and we can use them to calculate the distance to galaxies out to a few hundred million light-years (to my understanding). Beyond that, it's not currently possible to pick out individual stars.

      That does get far enough out so that doppler shifting becomes measureable, and we can check our doppler->distance function against Chepeid distances.

    • Why does this myth keep coming up?

      Educated people have known that the earth was round since antiquity. They weren't dumb and there was plenty of evidence - lunar eclipses, ships disappearing over the horizon, etc. They even had a relatively good estimate of the size of the earth.

      In fact, that's why Columbus had a hard time finding a backer for his journey. Everyone knew the approximate size of the earth. Columbus, the bozo, had the numbers wrong. He avoided disaster only because of incredible luck in hitting an unanticipated continent. Think of how different history would be North America were further west, if the Atlantic was the large ocean.

      The guy with no formal education and who never traveled more than a dozen miles from the place of his birth might have thought the earth was flat, but more likely he never thought about the shape of the earth at all. But he was no more the final word on "what people believed" than the trailer trash watching Jerry Springer is of our society.
    • Physics is all lies. I'm not kidding. And no serious physicist believes otherwise. We just look at existing data and try and make up some theory that "explains" what we're looking at -- and by "explain" I mean "predicts results the same as the experiment gives". Good theories also suggest other experiments to try, and predict what those results should be. If the experiment gives the predicted results, we're a little happier to keep using the theory.

      There's usually more than one theory (many, in general) to explain any given experimental result. And often several work equally well. Sometimes two theories give such similar results that you can pick whichever one's easier. (And that's usually what happens; this is what Occam's Razor is all about. Physicists are a lazy bunch.)

      And of course a lot of our theories are only valid at low energy (for example), just like Newton's Laws. A lot of work goes into figuring out just how fast we can go and still call it "low energy" for a given theory, so we know how fast we can go before we need to go through the work of coming up with a more complicated, higher-energy theory. (Theories almost always get more complicated at higher energy, because more can go on. Just look at Einsteinian Relativity vs. Newtonian Mechanics!)

      Physics is mostly approximations and emperical formulas. (Actually, the difference between a "law" and a "theory" is that a "law" is purely empirical -- it's the formula that best fits the theory, and was developed without worrying about the underlying mechanics. Deriving F=ma is a first year Physics lab, for example. :)

      (And no, we don't really know that a given star/galaxy is 8 billion lightyears away. Measuring distances, especially at intergalactic scales, is one of the biggest problems in astronomy.)

  • Whereas before the coolest material they could build stuff out of in Star Trek was Neutronium (Neutron Star matter), such as the hull of the Planet Killer in the old series episode "The Doomsday Machine", know they can build stuff out of quarkonium!! Whee.

    I'll go to bed now..

    • I know you're just joking. But on the subject of neutronium:

      It's only found in ultra-dense neutron stars. Neutron stars are completely composed of neutrons because under the immense heat and pressur electrons and protons combine, producing neutrons.

      I wouldn't try to build a spaceship. When you realease the ultra-pressure of neutronium, it inconvieniently produces a mega-explosion, with the neutrons and everything turning back into hydogen.

      It would be strong though, even for it's weight. Since nuclear forces bind it, neutronium would be ultra-strong. Nuclear forces bind neutronium because it has the density of an atomic nucleus. But the outward pressure of this high density substance is even more than the atomic forces can handle, so you would have trouble keeping it countained.

      Quarkonium would be even harder to contain and even stronger.

      All said, I suggest you use carbon nanotubes for your next spaceship hull. Much safer and easier. Plus your ship won't weigh as much as the moon.
  • I know the following isn't exactly about the article, but I've wondered about this for a long time:

    What would happen if you start dumping an huge amount of electrons in a black hole? As I understand it, the electrical force is far more powerful than the gravitational force. Therefor I wonder: what would happen if you create this huge negative pole? Would the black hole become unstable, would it eventually become impossible to add more electrons or something else (maybe the question is wrong altogether)? I anyone knows, I'd like to hear.

    • Re:black holes etc. (Score:3, Informative)

      by sigwinch ( 115375 )
      What would happen if you start dumping an huge amount of electrons in a black hole?
      The electric field near the event horizon would grow larger and larger. At some point, electron-positron pairs would start "precipitating" from the vacuum. The positrons would be attracted into the negative black hole and move its net charge toward zero. The electrons would be repelled away from the black hole. Incidentally, the mass of the black hole would be decreased in the process.

      Why? One way of looking at the vacuum is that it is filled with virtual particles. A group of virtual particles can "borrow" energy to spring into existence, and then annihilate after a short period of time, returning the borrowed energy to the vacuum. The time scale they are allowed to exist is governed by Heisenberg's uncertainty relation. (E*t>=h-bar.) For massive particles like electrons, it's a short period of time.

      If, during their short existence, the electric field can do more work on the particles than their borrowed energy, the "debt" to the vacuum can be "repaid", and the particles can become real.

  • Hum not to rain on anyone's parade but there are two things wrong with this article: First the article states:"The Chandra data gives the first evidence that they exist in nature." in reference to the strange quark. This is dead wrong, go look up a list of known and detected particles and you will find particle composed of, in part or in full, strange quarks, and if they are saying that we have never "seen" one they are right but this new data would not be any better detection than what we already have because: problemnumber two quarks cannot be unbound, if someone observes an unbound quark they are going to stockholm for free next year.

    So since I think the ppl involved with the Chandra experiment probably have their heads on straight the problems above are most likely due to an uninformed writer. The best I can figure is that they data suggests that the new object is composed of particles containing strange quarks but not entirely made of strange quarks. It would be easier to figure out if CNN actually gave credit to the ppl they got the story from.
    • Blockquoth the poster:

      "The Chandra data gives the first evidence that they exist in nature."

      I took this statement to mean, the first time the strange quark was observed outside of an accelerator.

      quarks cannot be unbound, if someone observes an unbound quark they are going to stockholm for free next year.

      Standard Model theories of the quark neglect any significant gravitational interactions, for the good reason that gravity is not accommodated in the Standard Model. Things derived for diffuse clouds of quarks on Earth might not apply for extremely dense collections of quarks in deeo space. Also, this doesn't seem to be "a" quark but many, many of them, the same way that a neutron star is many, many neutrons. I know quark stars have been predicted for a while now.

      The best I can figure is that they data suggests that the new object is composed of particles containing strange quarks but not entirely made of strange quarks.

      Well, the theory that gives rise to quark stars implies that, in sufficient numbers, strange quarks "assimilate" :) other quarks and make them strange, too. So I believe this is actually meant to be a big ball of just strange quarks. Of course, a neutron star is just a big ball of quarks, too (ups and downs, of course), so that isn't much of a theoretical leap.

  • pictures but no karma (Score:4, Insightful)

    by pagansage ( 142636 ) on Thursday April 11, 2002 @01:40AM (#3321651)
    Pictures of the two stars. [harvard.edu]

    and of course...


    NASA's full news release [nasa.gov]

  • Interestingly.. (Score:3, Informative)

    by deglr6328 ( 150198 ) on Thursday April 11, 2002 @02:17AM (#3321726)
    It wasn't mentioned in the Chandra [harvard.edu] release or the CNN spot, but RX J1856.5-3754 [nasa.gov] is apparently the closest known neutron star. The Chandra site states it's distance at ~400 lyr and the APOD site cites 180 lyr, practically in our back yard!(in cosmological distances anyway)

  • strange matter (Score:4, Interesting)

    by mghiggins ( 61851 ) on Thursday April 11, 2002 @06:43AM (#3322177) Homepage
    I did a PhD on pulars, which everyone thinks are neutron stars. At one point I found a paper which suggested that instead they might be "strange matter" stars - and it's always intrigued me how difficult it is to distinguish between the two.

    The cool thing about finding strange matter stars is that it suggests there's a lower-energy state of matter than our normal up/down quark pairings. No one's really sure because QCD is so hard to get numbers out of.

    Every time they build a new accelerator someone harps on this, worrying about whether we'll ram particles together hard enough to create a meta-stable bubble of strange matter. If there is a net saving in energy due to expanding that bubble (drop in energy due to increasing volume of lower-energy-state matter, increase in energy due to increased surface tension on the surface), the bubble will tend to expand and gobble up everything in its path - like the Earth, for example.

    That's the common worry, though it's easily allayed by noting that particles with much higher energy than anything we could create in an accelerator are hitting our atmosphere all the time, and none of them have turned our planet into a jiggling mass of strange matter.

    Anyway, interesting idea.
  • All known matter is made up of atoms in one of their four stages (solid, liquid, gas, and plasme). Each atom contains 3 known subparticles, neutrons, protons, and electrons. In turn neutrons and protons are each belevied to be made up of 3 quarks. There are no subparticles of electrons yet known.

    It is safe to say that all known stars contain quarks, though they are part of stable atoms. But, what would happen if there were no electrons and whatever ethreal particles they're made of? There is reason to beleive that without electrons quarks would have no reason to form into the protons and nuetrons (though its quite controversial). Now, imagine you had entire stars that had no, or more likely, not enough electrons. It is possible that the rest of the matter, quarks not formed into protons/neutrons, may comprise the vast majority of such stars.

    What impacts and/or uses this discovery have are not yet known, but it gives an insight into subatomic structure and how our universe may have formed. It also has some antimatter implications I won't get into. The most likely use comes from the fact that the bonds between quarks may be much stronger than the bonds between their big brothers.

    Oh, and I'm a high school student with way too much spare time. I don't claim to be an expert on this, but I do know a bit. Their may be some misleading things in what I've stated above, and some of it may just be wrong or unlikely. Just a little disclaimer, for I'm no resource on the subject. If you're that interested, go learn more about it.

  • Not so fast.... (Score:5, Informative)

    by Scott Ransom ( 6419 ) <sransom.nrao@edu> on Thursday April 11, 2002 @09:11AM (#3322655)

    I am one of the authors of a competing paper [uchicago.edu] on RX J1856 that was published yesterday, as well as a co-discoverer of the pulsar [harvard.edu] in 3C58. In my opinion these results, while definitely a possibility are certainly very preliminary. And in fact, there are other possibilities that make quite a bit more sense.

    In the case of RX J1856, there is a ~15% chance that the lack of pulsations (one of the biggest reasons for suspecting a quark star) is simply the result of an unfortunate emitting geometry or viewing alignment. Given that there are ~7 objects known that are similar to RX J1856, having at least one of them in this 15% seems quite likely to me -- and avoids having to invoke a new form of "star stuff".

    As for 3C58, the neutron star cooling problem can be mitigated (but not completely removed) by assuming a larger age for the supernova remnant (and therefore the neutron star) -- which expansion measurements and pulsar timing measurements also suggest.

    In other words, there are simpler explanations for the facts. Although those explanations certainly wouldn't get as much press...

    • It's a pleasure to hear from someone with real expertise in the area; thanks for the post. However, given that the vast majority of Slashdot readers aren't going to read both your paper and the Drake et al. preprint, you might consider posting a bit more detailed critique of their analysis. Their paper [lanl.gov] actually struck me as fairly reasonable, over-the-top press releases notwithstanding. While I agree that extraordinary claims require extraordinary proof, which they haven't really yet provided, there are some issues raised in their work that bear discussing.


      In particular, the lack of pulsation isn't quite the only thing pointing to something odd going on (as I'm sure you're aware, but some people might not be). They find a fairly good spectral fit to a 60 ev (700,000-ish K) blackbody, which yields a radius less than the 10-12 km or so allowed by current NS theories; while I haven't really gone over their paper in detail, they claim to have ruled out two-component blackbodies, at least at any level that would contribute appreciably to the flux, and power-law sources at high confidence. And while there remains some question as to the distance (the Walter (2001) measurements of 60 pc versus Kaplan et al (2002)'s 140 pc or so), I think their arguments in support of the larger distance (e.g., the larger distance is more in agreement with neutral Hydrogen column measurements plus standard physical density estimates) are reasonably compelling, albeit prone to criticism.


      I'd be curious to hear your thoughts on this -- i.e., do you think a much-lower temperature blackbody (or "hot spot" model) is not truly excluded by the data on this line of sight? Because the lack of pulsation here is just one part of the puzzle. :-)


      Cheers.

      • Re:Not so fast.... (Score:2, Insightful)

        by Scott Ransom ( 6419 )
        As for the spectral fits, their main objection to the two component fit (which is required to fit the optical data, BTW) is the lack of pulsations. But there is a ~15% chance of having no pulsations even _with_ a hot spot(s) and a two component blackbody.

        If there is no cool BB component, then they are correct that a very small radius is required -- and that could imply a quark star. I don't think this is the most likely answer, though (especially since it doesn't explain the optical data).

        As for the distance, I think that the 140pc distance is probably correct. There is a bunch of evidence pointing that way, and at least three people have independently analyzed the HST data and found the larger distance vs. 1 for the smaller....

        So in summary, I personally think that there is a two component BB, the hot supplying the x-rays, the cool supplying the optical, and an unfortunate geometry causes the lack of pulsations. This means that RX J1856 is just a normal everyday neutron star...
  • Oh I know the answer to this: Armin Shimmerman!

    *Happy he finally got to use DS9 trivia on Slashdot*
  • Trying to understand why we have some neturon stars and some quark stars. You'd have sufficient density/gravity/heat to overcome the nuclear force binding the neutrons together then they'd decay into quark stars, then as they take on more matter, they'd form black holes?

Slashdot Top Deals

Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (7) Well, it's an excellent idea, but it would make the compilers too hard to write.

Close