Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 


Forgot your password?
Close
typodupeerror
×
Space Science

The 1st Generation of Stars 236

Posted by Hemos from the looking-into-the-past dept.
Andy_Howell writes "Astronomers may have found members of the first generation of stars in the universe. Using the Hubble Space Telescope and the Keck I telescope, they observed a faint red blob that had been magnified into a double image by a gravitational lens. The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old. The clump appears to contain only about a million stars, and is less than a few million years old. It is thought that swarms of these clumps came together over the age of the universe to create the galaxies we see today."
This discussion has been archived. No new comments can be posted.

The 1st Generation of Stars More

The 1st Generation of Stars

Comments Filter:
  • cool, very cool.

    • Re:cool (Score:3, Funny)

      by jd ( 1658 )
      No, I think you'll find those stars are actualy quite hot. Well, were. I guess they're cool -now-.
  • Nice to actually see where our universe came from...and weird to be looking so far back in the past!

    Now for a serious question - what's with the red colour? If these stars were that new when they emitted this light, wouldn't they be bright blue?
    • Redshift Doppler effect? False coloring in the image?
    • Red shift?
      • OK, go on, explain it to me! From what I know, Doppler is when the source is moving relative to (in this case away from) the viewer. How can we be moving so fast to have an effect on light?!

        • Re: Red Shift (Score:2, Informative)

          by istvandragosani ( 181886 )
          Because it's not relative *constant* motion. Reputedly, due to the expansion of the universe, things father away appear to be moving away from use faster than things closer to us. This also means the light itself is being expaned -- shifted towards the red.

        • Re: Red Shift (Score:3, Informative)

          by big_hairy_mama ( 79958 )
          It is by observing the doplar shift, or "red shift", in the wavelength of a stars light that the length to almost every distant object is measured.

          Think of yourself as being on the surface of an expanding baloon: relative to other objects that are close to you on the surface, you are moving very slowly. Relative to objects at the center of the baloon or halfway around the surface, you are moving a little faster (remember this is as the crow flies). Relative to objects clear on the other side of the baloon, you are moving the fastest of all.

          On the scale of the universe, objects on the other side of the galaxy are moving extremely fast (relative to you). I'm not sure exactly how fast, but I remember reading somewhere that it is getting close to the speed of light (after all, they have had to cover a huge amount of space to get so far away). This is easily fast enough to have an affect on the wavelength of the light - even a small relative speed will have a small (but probably unmeasurable affect).

          IANAAstroPhysicist, so whether this explains the visibly red shift (since scientific spectrographs are much more sensitive than our eyes ), I cannot say. Another explaination might be that the stars are young and therefore cool, but I couldn't say that for sure either.

          • Re: Red Shift (Score:2, Interesting)

            by Captn Pepe ( 139650 )
            IANAAstroPhysicist, so whether this explains the visibly red shift (since scientific spectrographs are much more sensitive than our eyes ), I cannot say.

            Bingo! The article mentioned that this star cluster was found at a redshift of z=5.58 I believe. The formula of interest here is that

            1+z=(Lamda_em - Lamda_ob)/Lamda_ob

            This means that the light we observe from this star cluster is arriving at a bit less than a quarter of its original wavelength -- the red light seem in the picture was emitted as hard ultraviolet radiation from young massive stars! Yes, young stars are really hot.

            If you think that's impressive, consider the quasars the Sloan Digital Sky Survey keeps finding out at z>6. We see them as faint red dots, but they are actually outshining entire galaxies, mostly in the form of hard X-rays. And then there's the cosmic microwave background, sitting out there at z~1300. That was once a sea of energetic photons, just slightly too cool to ionize all the hydrogen in the universe; now it is a 2.7 degree Kelvin hiss in your radio.

            Executive summary: you'd better believe you can see cosmological redshifts.

            Oh, and PS -- don't ever call it a "doppler shift", that really pisses off cosmologists (or at least the ones in my department). Doppler shifts are the result of objects moving toward/away from you emitting photons that are a different wavelength in your rest frame. In the case of cosmological redshifts, the objects in question are not only not moving away from us, but general relativity doesn't even have a concept of "relative velocities" on these scales. Instead, the photons are actually arriving with a different wavelength, because space expanded underneath them en route.

            If you aren't sure there is a difference, try this thought experiment: an observer and an emitter are at relative rest in a static universe, when a photon is emitted. While the photon is in transit, the observer and emitter move farther apart, then come to rest again. The observer sees the photon at its original wavelength, since the motion occurred totally independantly of the photon. Now imagine that, while the photon was en route, the universe expands for a little while. The observer and emitter are in the same end state (i.e. farther apart and at relative rest), but the photon arrives with a reduced wavelength, because this time space expanded underneath the photon.

          • Another explaination might be that the stars are young and therefore cool, but I couldn't say that for sure either.

            It turns out that there are certain spectral features (element emission/absorption lines) that occur at the same frequency no matter what temperature the object producing them is at. If this pattern of lines is shifted, you know that the colour is due to a real redshift and not a temperature difference.

            I suppose that if something like Planck's constant was different at the time and location of the stars, that would also produce an emission line shift, but it's far more likely that the light has just been redshifted.
        • The frequency of the waves occurs farther apart. Thus we see a redder color. Same light. Same intensity. Same speed. Just the frequency changes. The way it was originally tracked was with the very prominent calcium absorption lines on a spectrograph. I learned all about it as a kid watching an episode of cosmos, which I still have on videotape. Even on the blurry 1920's spectrometer slides that Hubble and Humison used, the effect was dramatic and immediately obvious.

          I don't recall the actual length of visible light waves, but I think it's in non-microscopic units. At extreme distances, the expansion of the universe probably means our relative speed to those objects is extremely high. What we see as the red light may have started in the ultraviolet at the source . . .

          • Re: Red Shift (Score:2, Informative)

            by Mr. Slippery ( 47854 )
            I don't recall the actual length of visible light waves, but I think it's in non-microscopic units.
            Visible light is in the hundreds of nanometers. Much smaller than "microscopic".
            • Thank you. It's been awhile. I think I was thinking about sound waves and light waves at the same time. Audible sound waves (at least the bass ones, which are all I care about) are all in feet and inches . . .
    • Stars are usually formed from nebulae, the dust from which blocks most light, but less of the longer wavelengths like red and infrared. So we see mostly the red light.

      More info can be found on the NGST Science Page [nasa.gov].
    • It's mentioned that the stars are composed mainly of Hydrogen, which accounts for the red. Also, with something so far away, we see something called "red shift". Basically, things farther away from us are moving away from us faster than things close by. For things extremely far away, the red shift is caused by the doppler affect expanding the light waves and shifting the color towards the red end of the spectrum. Likewise, the few objects that are moving towards us experience a blue shift -- the light waves are slightly compressed. However, due to the expanding universe, this is very rare.
    • According to the article, it's because they're only made of hydrogen. (The other elements only get created as the first generation burns out/explodes.) All other elements on Earth came from a previous generation of stars.
    • The actual article, especially the picture byline explains that due to the youthful nature of these stars, most of the fusion at the time is pure hydrogen, which gives off a very narrow, characteristic light from energy emmission. Only as a star gets older do other wavelengths begin to be emitted.

      Redshift would alter the base frequency as well, but the article mentions that it's due to the age of the stars.

      • If the stars are fusing hydrogen, they are giving off a blackbody spectrum, not hydrogen recombination lines. In fact, if the stars are pure hydrogen, it's likely that the spectrum is going to show a pretty deep absorption feature at the H-alpha wavelength, not an emission feature, although it depends on the surface temp of the star. I would guess that these stars are probably hot enough, that all the hydrogen has been ionized, and probably stays ionized, such that you probably wouldn't even see the absorption feature.

        It's probably the case that these are very hot stars with peak emission at blue or uv wavelengths. The reason for the red color is probably almost entirely due to the red shift of the objects, and possibly a small amount of interstellar dust (depending on how much intervening dust there is).

        More often you see H-alpha emission from the gas clouds surrounding newly formed stars in star forming regions and such, it's somewhat rare (although not unheard of) to see strong hydrogen emission in a stellar atmosphere.

    • Now for a serious question - what's with the red colour?

      The other question is if we are peeking over into the backyard of the next universe over, where stars may be burning out. [smile]

      but seriously, all of the stars of about the same age. and there is some red shift going on there.

      But they may just be sufficiently small that they never reach bright blue. They may be just big enough to for the reactions to catch, without blowing them apart. and wind up being red.

      • But they may just be sufficiently small that they never reach bright blue. They may be just big enough to for the reactions to catch, without blowing them apart. and wind up being red.

        To some extent that makes sense, but on the other hand it's rather rare for us to see most red dwarves. It's been theorized that the majority of the stars in the universe are probably red dwarves, but we just can't see them because they're so faint. Also, due to the fact that the larger a star is, the brighter it is and the faster it burns. Comparatively regular stars burn like a flash in the pan compared to red dwarves which burn (relatively) cool and many times longer than their larger counterparts (thus the number of red dwarves tends to accumulate over time). Well in any case I find it unlikely that light could travel that far, for that long, and actually be from a cluster of red dwarves - which I'm sure would be far to faint for us to detect. It is however possible that some of the very first red dwarves are still burning if I remember correctly.

    • Re:Cool! (Score:2, Informative)

      by StupendousMan ( 69768 )
      The stars WERE hot and blue when the emitted
      the light we are now seeing; if you had looked
      at the spectrum of the starlight back then
      (because you were floating in space close to
      the stars), it would have peaked in the
      ultraviolet.

      However, the light has travelled a long way
      to reach us, and the universe has been expanding
      since then. The redshift of these objects is
      around z=5.58, which means that we observe photons
      to have a wavelength (z+1) = 6.58 times longer
      than their rest wavelength. The peak of the
      spectrum has moved from the near UV to the near
      infrared. Hence, the stars would appear red
      if viewed by a person.

      The pictures were formed by combining images
      taken through several different filters with
      HST. Each filter was in the visible range.
      The astronomers who made the picture set the
      Red plane of the image to correspond to the
      picture taken in the reddest filter,
      the Green plane to the filter of intermediate
      wavelength, and the Blue plane to the bluest
      filter. It's false color, but reasonably
      like a person would see.
    • Red color? Redshift from Hubble Expansion.

  • I'm amazed (Score:2, Offtopic)

    by Inthewire ( 521207 )
    ...that this article did not mention the Big Bang.
    If you are interested there is a spectacular book entitled _The_Big_Bang_Never_Happened_ that describes an alternate (and far more rational) cosmology...it posits that the universe is ruled by elecromagnetically active plasmas, and that the behaviors of our universe need not be explained by increasingly unlikely constructions.
    • ...a link would be nice, please.
    • right on! and if you drop the big bang theory, you suddenly don't need all those wacky super strings and shadow matter theories that scientists have to keep coming up with to support the big bang >theory

      ...
      • Who says those are necessary to support the big bang? Aspects of quantum mechanics and all sorts of other phenomena, not to mention the effort to marry Relativity and Quantum mechanics, require a new "whacky" theory.

    • Re:I'm amazed (Score:3, Informative)

      by MaxGrant ( 159031 )
      a spectacular book entitled _The_Big_Bang_Never_Happened_

      Sensational is more like it. I tried to get into it in the bookstore one time, but every time the author got up to the really juicy part where he was going to explain everything, he dropped his thread and referred me to a later chapter. Also, he was attacking mostly the exterior consequences of Big Bang theory, and as I recall he failed to really get to the main premises. I opted to put the book down. It looked like a crank to me.

    • Re:I'm amazed (Score:4, Informative)

      by sigwinch ( 115375 ) on Friday October 05, 2001 @04:05PM (#2393483) Homepage
      If you are interested there is a spectacular book entitled _The_Big_Bang_Never_Happened_ that describes an alternate (and far more rational) cosmology...it posits that the universe is ruled by elecromagnetically active plasmas...
      I read that book, and in my opinion it is completely full of shit. This is also the opinion of other actual scientists who have reviewed the book.

      The author is intellectually dishonest: at one point he is discussing some electromagnetics simulations that have a spiral galaxy-like appearance, and saying how those support his cosmological electromagnetism theory. What he doesn't tell you is that the images are *cross sections* of tubular structures, and that the field strengths needed to create those structures are *enormous*.

      If that BOOK were posted to USENET it would be UTTERLY INDISTINGUISHABLE from the other PHYSICS CRANKS.

    • "Increasingly unlikely constructions"? You mean like a universe ruled by electromagnetically active plasmas?
    • If you are interested there is a spectacular book entitled _The_Big_Bang_Never_Happened_ that describes an alternate (and far more rational) cosmology


      What does "far more rational" mean? In any case, the Big Bang theory has a lot going for it. It explains why space is expanding, it explains the relative abundance of elements in the universe, and it explains the 3K background radiation.


      For any other theory to supplant the BB, it has to explain the data equally well. I haven't read the book you mentioned, but the active plasma idea sounds like BS to me. :-b

    • Re:I'm amazed (Score:1, Funny)

      by Anonymous Coward
      Interesting. I've never liked the idea of a Big Bang because it seems to contradict everything I have been told. Of course those who told me these things have never looked through a telescope, even less measured the redshift of galaxies or the cosmic background radiation, but they were the first to tell me how things were created, and that's that.

      So I'm ready to beleive in anything other than the big bang because, if I'm going to admit that I was off-track all of these years, at least I can take confort in thinking that those bigbang scientists were wrong too. With a new theory, we're all equal and starting anew, it's not like I'm 50 years behind the curve anymore.

    • Re:I'm amazed (Score:3, Informative)

      by dragons_flight ( 515217 )
      It presumes the Big Bang, or something like it. Obviously you can't have young hydrogen-only stars unless the universe was different than it is today.

      Either the universe exists into the arbitrarily distant past or it has some kind of a start. I've never heard a good hypothesis for a beggining to the universe that doesn't involve some sort of a big bang. Which premise is that book trying to sell? That we always existed?, or that we started from something other than a big bang?
    • sorry, but string theory supports the big bang.....I am interested to find out how he trys to explain the red shift and sigularities using his theor.....hypoth.....no......no....fanticy.
    • a spectacular book entitled _The_Big_Bang_Never_Happened...

      I remember that one. IIRC, one of its big arguments against the Big Bang was that the theories made no verifiable predictions. At about the same time I read those arguments I read the first stories about how the COBE experiment had detected the variations in the cosmic microwave background that inflationary theories had predicted.

    • Alternative Cosmology... (Score:5, Insightful)

      by Boulder Geek ( 137307 ) <archer@goldenagewireless.net> on Friday October 05, 2001 @04:40PM (#2393646)
      And why you should be very, very skeptical...

      The problem with "The Big Bang Never Happened" (which I have read) and other alternative cosmologies is that they don't even attempt to go deep enough to prove their points. There's a reason for this. All of modern cosmology is based on General Relativity. If you are going to say that the Big Bang Never Happened, then your alternative cosmology has to not only come up with an alternative explanation for the Universe, but also explain everything that GR does without having a Big Bang. This is a very tall order.

      It isn't enough to point out the contradictions in the standard model. It is also necessary to build a new model that explains all observations. To date, no one has been able to do this without having a Big Bang at the start.

  • What if the universe were to wrap around itself, and we were actually staring at our backs? If there were some ultra-ultra-mega-super-densely packed gravity well or something in the center of our universe, we'd be going, "Man..thats an old ass.." but we'd be staring at our own and stuff.

  • Wowsahhhs (Score:3, Funny)

    by ekrout ( 139379 ) on Friday October 05, 2001 @03:51PM (#2393387) Journal
    Astronomers may have found members of the first generation of stars in the universe.

    U GOTS TO B KIDDING ME..........BRITNEY SPEARS IS LIKE THE FIRST AND BESTEST EVER ... THERE AINT NO STARS B4 HER IN MY BOOK!!!!!!!!!!!! I LUV BILLY!!!!!!!

  • There are tons of little red dots all over that image. How can they distinguish that those two are so special?
    • Each dot on that image is a galaxy/star/something. The color of the dot is what's interesting -- the redder it is, typically the further away it is. If you look at the big image, there are a lot of dots, but they're only slightly reddish. The two "interesting" ones are extremely red, indicating that they're very far away. Astronomers have shown that, since the universe is expanding, things further away from us are moving away from us faster and faster. The end result is that the doppler shift caused towards the red end of the spectrum gives us a quick indication of how old things are, and hence, how interesting they might be.

    • Re:how do they pick those out? (Score:1, Informative)

      by Anonymous Coward
      They're not just looking at it with red, green and blue CCD sensors -- Imaging Spectrometers [gemini.edu] give you a readout of the full spectrum, including characteristic bright (emission) and dark (absorption) lines. The position of these lines in the spectrum changes with distance (red shift due to expansion of the universe) which looks a lot different from just a naturally red star. In fact their estimate of the age of the galaxy is based mainly on how far the lines have shifted!
    • Don't forget that the image is actually a visual representation of extremely complex data. Those "little red dots" are just the result of reducing the usefulness of the information to create something pretty to look at. The signifigant parts of the image are picked out by computer algorithms specifically designed to pick out the signifigant parts. Eyeballing it just doesn't cut it.
  • Here's a link to the original [sciencenews.org] [sciencenews.org] publishing of the article.

    -Berj

  • Age of the universe? (Score:4, Interesting)

    by sjbe ( 173966 ) on Friday October 05, 2001 @03:55PM (#2393418)
    The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old.

    Perhaps I've been out of touch with my astronomy studies for too long, I know there are a lot of discoveries being made. However I was under the impression that there was still a great deal of uncertainty about the age of the universe. It was generally agreed that it was somewhere between about 13 billion and 20 billion years old but exactly how old wasn't/isn't clear.

    Is there something I don't know about or is this age prediction just an assumption? Have there been some consensus on this recently that I didn't hear about? Anyone know for sure? I'm always suspicious when I see "discoveries" like this whose results depend on something that hasn't been definitely proven.
    • Very interesting idea. Perhaps our technology hasn't developed enough to see further into the past, or even more likely, perhaps not enough time has elapsed for the older light to reach us yet. Anyone of the thought-to-be empty pixels on the picture could in fact be filled in with a red pixel all their own, at some point in the near or very distant future. The best they can ever hope to do is a >= statement.
    • Good point; I'm also suspicious of people coming to conclusions over things that may have happened billions of years ago. After all, there are things that we can actually see and touch (like diseases, natural phenomena, etc.) that we still can't figure out. What makes people so sure that they've figured out things that are so unfathomably far away in space/time?
      • What makes people so sure that they've figured out things that are so unfathomably far away in space/time?


        First of all, what makes you think they're all that sure?


        Second, do you remember how science works? Collect evidence, formulate a theory, use the theory to suggest more evidence to look for, look for that evidence, lather, rinse, repeat. All you're seeing is the output of that cycle. Doesn't mean the answer is RIGHT, it just means that it's an answer that fits the evidence. Got a better answer that fits all the evidence? Bring it on!

    • Re:Age of the universe? (Score:5, Informative)

      by TMB ( 70166 ) on Friday October 05, 2001 @04:22PM (#2393562)
      The current best estimate of the universe, mainly from measurements of the Cosmic Microwave Background and Type Ia Supernovae, consistently give results around 14-15 billion years, leaning towards the lower half of that range.

      In any case, the number "13.6 billion light years" is relative to the actual age of the universe. What was measured was a redshift of 5.58. You can map that into a lookback time, but it depends on the cosmological parameters you assume. The beginning of the universe is at redshift infinity, which will give you another lookback time (ie. age of the universe) that depends on the cosmological parameters.

      I don't know what particular cosmology was used to map z=5.58 to 13.6 billion years lookback time, but the STScI press release mentions that the cosmology they used gives an age of the universe of 14 billion years. It's probably a "concordance model" flat universe with 0.3 of the closure density coming from matter and the rest from the cosmological constant, with a Hubble constant around 65-70 km/s/Mpc.

      [TMB]
    • Well, although the writer makes an indirect implication that isn't quite accurate, yes, there's news you've missed -- namely this article.

      An interesting thing about this discovery, if I'm reading it correctly, is it could be a good indicator of the universe's age. It correlates two different facts:

      the spectra of the stars suggest that they are _uniformly_ extremely young. This makes it likely that they were all formed when the universe was very young.

      the red shift of the cluster indicates it's 13.6 billion light-years away.

      So, it's a sighting of an "event" that could only have happened in the early universe, and since the light from the event took 13.6 billion years to get here, it means the universe is just over 13.6 billion years old.

      Now, mind you, this is not enough evidence to be certain about that leap, the "red shift" fact has a wide margin of error (since the constancy of Hubble's constant is now in question) and there may be situations where a cluster like this could occur in the universe much later than its early epoch, but it could reduce the wide gap in universe age measurements.
  • Once again I'll say it: astronomers kick butt. Who else can say with relative certainty what happened 13 billion years ago, and back up such claims with observational data?
  • How many light-years across is the universe? If this light is really 13.6 billion years old, why didn't it pass the earth a long time ago? Shouldn't it be out re-defining the "edge of the universe"? Or maybe it's like the game astroids, where your ship goes off the edge of the map and reappears on the other side?

    james
    • How many light-years across is the universe? If this light is really 13.6 billion years old, why didn't it pass the earth a long time ago?


      AFAIK (I could be wrong), the radius of the observable universe is thought to be somewhere around 15-20 billion light years. So to answer your question, the reason it didn't pass us is that it hadn't gotten here yet. :)

    • The general scientist-approved age of the universe is between 10 and 20 billion years (in US counting), starting with the Big Bang. The edge of the universe is expanding at the speed of light. So from the center to the edge (the radius)is 10 to 20 billion lightyears. Since they estimate the cluster to be over 13 billion years old, it is probably located on the other side of the center of the universe. The reason the light hadn't passed Earth yet is that we are that far towards the edge of the Universe. If we were located in a galaxy closer to the center of the universe, the light from the clusters would have passed us a few hundred million years earlier.

      As for the the actual "edge" of the universe, there are many theories of how it actually exists. Some say it _is_ like the Asteroids game, looping upon itself. Others say there is just a void after it which we can never get to because the edge retreats from us at the speed of light. And others say there is no edge, space is infinite.

  • Just curious. (Score:2, Troll)

    by perdida ( 251676 )
    Is there any application for this kind of astronomy?

    If I were a director of federal astronomy I would enthusiastically fund near-galactic research that searched for wormholes, civilizations, planets that could support life, etc -- any kind of knowledge we need for a feasible star economy.

    Basic science is nice, but erstwhile star captains probably wouldn't find the universe's origins very relevant.

    • Why Curisoty Based Research? (Score:4, Interesting)

      by JohnDenver ( 246743 ) on Friday October 05, 2001 @04:22PM (#2393561) Homepage
      "It is a profound and necessary truth that the deep things in science are not found because they are useful; they are found because it was possible to find them." -Robert Oppenheimer

      Robert Moody from the Department Mathematical Sciences, University of Alberta illustrates the importance of curiosity based research in his paper [math.mun.ca] using lasers as an example of why curiosity based research is necessary.

      Carl Sagan in his book, The Demon Haunted World, also stresses the importance of curiosity based research using James Clark Maxell's discoveries as an example of how it effects our lives today by providing the necessary building blocks for radio, television, computers, lasers, etc.

      Basic science is nice, but erstwhile star captains probably wouldn't find the universe's origins very relevant.

      It may not seem very relivant at first, but there are those who would argue in order to even begin to piece together data for a theory of everything (which may be vital to even approach the idea of star captains), we need to gather as much data as possible to reduce our error bars of knowledge.

      All in all, Good question... I'm sure some of you have better answers...

    • Hello? See the adequacy.org link in the .sig? Don't feed the trolls.
  • The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old.

    How is this possible? When the universe was less than a billion years old, then any two particles in it would have to be within two billion light years of each other, assuming the "big bang" model is true. It could not take light from one of them 13.6 billion years to reach the other.

    What's wrong with my reasoning?
    • Two points 2 billion light years from each other could be moving apart very rapidly. Light leaving point A will need to cover more than 2 billion light years before reaching point B.

      A train leaves new york at 3:00 heading north...
      • I don't see how this works in reletivity.

        No matter how fast they are moving away from each other, light still travels the same rate. Therefor the light should arrive in no more than two years.

        In other words, if a car is moving away form you at near the speed of light, flashes its turn signal...

        • Re:How is this possible? (Score:3, Informative)

          by TMB ( 70166 )
          The horizon expands.

          When the universe was two billion years old, no one object could receive information about anything farther than two billion light years away. But a billion years later, there is time for information to have come from objects that were originally outside of its light cone, but the light cone (in this case called a horizon, because it can't be seen beyond) has expanded beyond them.

          [TMB]
        • light still travels the same rate


          Not quite. All observers will measure the same pulse of light as travelling at the same speed. That's not quite the same thing.

          • right, you have an observer at one point, and an observer at another. The speed of light is still constant across the distance of one light year no matter how fast your traveling in any direction.
        • They are moving away from each other because the universe is expanding. The amount of space between the two points is increasing as the light travels between. Relativity imposes no limit on how fast space can expand. During the inflationary era, the Universe expanded faster than the speed of light.
    • >The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old.

      How is this possible?

      The quotation is misleading/unclear. I believe what they are trying to say is that the blob is 13.6 billion light years away from us right now. They estimate that what was seen of the blob is from when the universe was less than a billion years old. (This implies the universe of today is less than 14.6 billion years old)

      This also wouldn't violate relativity as one poster was concerned about.
    • Let's look at this classically. The classical picture is not correct, but it can give some rough idea of how this is possible.

      We have two objects moving apart in the early universe. Classically, the distance D between them will be the relatvive velocity, v, times the age of the universe at the time the light in question was emitted.

      So lets say D = v*1 Gyr (10^9 years)

      Now light from one get's emitted and starts travelling towards the other at the speed of light, c.

      In order to see the light from the other source, it has to catch up to us. In other words c*t = v*t + D, where t is the time since the light was emitted.

      Substituting for D and solving for v, we get v = c*t/(t+1 Gyr). Hence in a strictly classical approximation, the two objects must be travelling apart at a relative velocity of 0.93c, in reality relativity and cosmology would probably tell you they don't have to moving apart nearly that fast, but the idea is there.

      If two objects are moving apart fast enough it will take the light from one a long time to catch up with the other.
  • I'm writing my thesis on the compressibility of floating-point numbers (an understudied aspect of computer science), and I need more Real-World data to study. Astronomy being a field requiring vast storage capacity this is the perfect data to use (and physics too if I could find it). Anyway, I need data to statistically analyze. Is the data for this project open, and where can more data be found? I'm primarily looking for LOOONG streams of floating-point numbers.

    Thanks for any help you can give me.

    My email is gcshaw@amherst.edu
    • Not sure if you're serious or not: if you're serious, there are tons of data out there, all public and for the taking. However, I think your project is somewhat fishy: most astronomy data is "noiselike" and random, so it really shouldn't compress very well. (Of course, I'm talking about packed floats, not ASCII representations.)

      Anyhow, assuming you're serious:

      • Try radio astronomy data. For example, pulsar searches (related to what I do, forgive my bias) use simple time series data I(t) which would seem to be ideal for your work. Try this: http://www.atnf.csiro.au/research/pulsar/pmsurv/
      • HST data is always available for download, once the proprietary period has expired, from the HST archive [stsci.edu]. You don't care what the data is from, right? Note, though, that this is a 2-dimensional image, so it might have some "fake" compressibility due to redundant information. Radio data does not have this weakness, so I recommend that instead.
      • For most astronomy data, you'll need to learn to read FITS format: try this [nasa.gov].
      Hope this helps - if you're serious and need help, feel free to drop me a note. (shami at astro dot cornell dot edu)

  • Am I the only one who finds Gravitational Lenses to be kind of creepy? Photons leave a star on different paths, eventually become separated by many thousands of light years so that entire galaxies separate them, then get deflected so that they eventually converge to within inches of each other just as they hit the surface of planet earth. Those are are some tall odds.

  • Maybe this is a stupid question but...



    How does a galaxy cluster bend light that started out before the galaxies were born?



    I'm assuming that the light from the 13 billion year-old stars is travelling at light speed and that the galaxy cluster lenses are younger than 13 billion years. So how does the lens get ahead of the light and bend it? Has the light has been slowed down?

    • The same way a bus bends your bike...

      You start off down the road, heading for the intersection. There is no bus there. However when you get to the intersection a big bus comes and runs you over. It was't there when your trip started but it appeared just in time to intercept you.
    • The light doesn't get ahead. The systems are simply too far apart for the light to reach from one to the other right away. Think about it. Even if the two systems were the same age, if we are closer to one of them, it will appear more developed, simply because its light reaches us sooner. So, by the time the *early* light from the distant system reaches us, it's already in the path of a galaxy cluster. For all we care, right now there could be a huge black hole there, where we are now seeing young stars...but we won't find out until another 13 billion years or so.
  • In a later press release the scientist were quoted as saying, "Ooops! We thought we saw starts BILLIONS of miles away that had been magnified through a gravitational lense, but what we actually saw were some stains from an interns habit of dribbling coffee."

    Excuse my cynicism (and my poor spelling), but they're trying to tell us that they're capturing light that was generated billions of years ago. Enough light to charge an optical receiver. I'm currently working on a project that has to generate laser light down a fiber, and pick up the signal after on a few miles, and we're having problems doing that. Occam's Razor applies here, and in my mind there are a mountain of explanations that fit better. Simple noise would be the first one. A body that is much closer but shrouded by some sort of haze is another. Even if space were nearly completely empty, wouldn't there be enough dust after a few zillion miles to make it opaque.

    Just how much can we trust people claiming to see ghost (things that may very well be there, but no one else can see them)?

    • Re:Ooops! (Score:5, Informative)

      by jd ( 1658 ) <imipak@ y a hoo.com> on Friday October 05, 2001 @04:34PM (#2393608) Homepage Journal
      The answer is actually quite simple. You use a photon multiplier device, a very large telescope, and a very long baseline.


      Ok, now for the more complex bit, actually saying what these are.


      A photon multiplier is a device which takes in a stream of very low energy photons and generates a stream of much higher energy photons, as a result. It's a basic amplifier, for photons.


      A very large telescope gives you a huge collection area. The larger your collection area, the more light you gather. By squishing that light into a much smaller area, you essentially generate a much brighter image.


      The same is true of a long baseline. The idea, here, is to increase the time over which you collect the light. Double the time, double the light.


      The consequence of using all three techniques is that you can easily collect a few photons from a vast distance, and turn them into an actual, visible image. But don't expect it to be easy. I imagine that the Hubble Telescope had to be pointed at that same spot for 24-48 hours, to generate such a view.


      (When you recall that the Earth is rotating on its axis, that it's also rotating round the sun, and that the sun is moving round the galaxy, and that the galaxy has its own motion relative to other galaxies, and that ALL of these are complex, N-body problems, the challange of being able to keep the telescope pointing at a tiny cluster, billions of light-years away for more than a few seconds is an achievement. To manage it for maybe 1-2 DAYS is staggering.)

    • Excuse my cynicism (and my poor spelling), but they're trying to tell us that they're capturing light that was generated billions of years ago. Enough light to charge an optical receiver. I'm currently working on a project that has to generate laser light down a fiber, and pick up the signal after on a few miles, and we're having problems doing that. Occam's Razor applies here, and in my mind there are a mountain of explanations that fit better.


      Well, why don't you ASK 'em? (Or maybe do a little research on the topic.) Astronomers have been working for decades on techniques of more and more efficiently capturing photons. Supercooled charged-coupled devices are now all the rage. And don't forget, they are using telescopes with lenses 8 meters across, thus a LOT more light-gathering power.

    • Re:Ooops! (Score:5, Informative)

      by TMB ( 70166 ) on Friday October 05, 2001 @04:53PM (#2393708)
      >Excuse my cynicism (and my poor spelling), but they're trying to tell us that they're capturing light that was generated billions of years ago. Enough light to charge an optical receiver. I'm currently working on a project that has to generate laser light down a fiber, and pick up the signal after on a few miles, and we're having problems doing that.
      Do you have surface 78 square meters to collect the light? (the size of the Keck telescope that took the spectra) Or a surface 3.2 square meters but that doesn't have any obstructions in the way? (HST, which took the image) Do you have blank backgrounds all around that you can compare against? Do you have years to analyze the data, or do you need to do it real time? It's a very very different kind of problem.

      >Simple noise would be the first one
      Looking at the images, they look like they've got pretty good S/N. I haven't seen the spectra, so I can't comment on that, but if they have spectra for the two different images that both give the same redshift, that's not likely noise.

      >A body that is much closer but shrouded by some sort of haze is another.
      Then it's haze that happens to shift all of the photons redward by a factor of 6.58. In both images independently. And doesn't make them fainter.

      >Even if space were nearly completely empty, wouldn't there be enough dust after a few zillion miles to make it opaque.
      That's an interesting topic. All dust that we see in the universe is inside of galaxies, and preferentially blocks red light. So the places that you'd expect dust to make a difference is in the galaxy itself, in the Milky Way, or maybe in the cluster that's lensing the images (if you can come up with a way of expelling the dust out of a galaxy into the intracluster medium without destroying the dust, which isn't easy to do - dust is pretty fragile)

      The only possible evidence for gray dust in the voids between large scale structure is as a way out of having the Type Ia Supernova measurements argue for the existence of a positive cosmological constant - some have argued that the reason that the supernovae are fainter isn't that they're farther away, it's that there's some fairly uniform gray dust (it can't be normal dust because then it would preferentially block red light, and we don't see that happening) that is absorbing some of the light. But there is plenty of other evidence pointing towards a positive cosmological constant, so the dust explanation is unlikely.

      Hope that helps. :-)=

      [TMB]
  • Any sign of a Starbucks?
  • A trivia point, for those interested. Helium was named for the sun, helios, first discovered when spectroscopy was very young. This element was not yet discovered on the earth and was thought only to be a "heavenly" element. That is until some researcher was told that if a piece of pitchblende was placed underwater, bubbles would form. He collected these gas bubbles in an inverted flask and analyzed them with the new spectroscope and found it to be helium.

    Helium today mostly comes from mines. They are called mines and not wells because they produce a mineral but are essentially just like natural gas wells. This gas comes from radioactive decay which produces alpha particles---helium ions---which then capture electrons from its surrounding and becomes helium gas.
  • "The blob was found........."
    "The clump appears to......"

    Is it just me or is Slashdot turning into less a tech website and more a B-movie? ;)

  • Great photo!! (Be sure to click on it to see the higher-res copy.)

    It amazes me that there are so many galaxies that each of us could own one. If we each owned a galaxy, then each of us would own more stars than there are people on Earth.

    There's plenty of energy in the universe, it's just not always where you need it.


    ABC News article: "Abu Sayyaf ... train[ed] terrorists in the methods taught by the CIA ..." What should be the Response to Violence? [hevanet.com]

  • -1 No heavy elements (Score:5, Funny)

    by isomeme ( 177414 ) <cdberry@gmail.com> on Friday October 05, 2001 @04:38PM (#2393628) Journal
    Most astronomers had previously ignored these stars, which had been modded down heavily for posting annoying "First star!" messages.
  • //The blob was found to be a cluster of stars 13.6 billion light years away, seen when the age of the universe was less than a billion years old.//

    Did we find out the exact age of the universe while I was on vacation or something? Why didn't someone tell me?

    I sure hope that when someone discovers the meaning of life, or the existence of an afterlife that I'm not out of the loop on that one, too.
  • ...The People's Republic of China launched their first intergalactic starship toward the red blob, on a mission to begin diplomatic relations with this clearly Communist star cluster.

    One political analyst pointed out the remarkable similarity between the cluster and the birthmark on Mikhail Gorbachev's head.

    Publication of a Little Red Datacube has been started in Shanghai.

Slashdot Top Deals

Beware of Programmers who carry screwdrivers. -- Leonard Brandwein

Close