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Space Science

Milky Way Is Twice the Size We Thought 301

Posted by kdawson
from the everything-you-know-is-wrong dept.
Peter writes to tell us about a research group at the University of Sydney in Australia, who in the middle of some calculation wanted to check the numbers everybody uses for the thickness of our galaxy at the core. Using data available freely on the Internet and analyzing it in a spreadsheet, they discovered in a matter of hours that the Milky Way is 12,000 light years thick, vs. the 6,000 that had been the consensus number for some time.
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Milky Way Is Twice the Size We Thought

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  • Haha (Score:5, Funny)

    by Anonymous Coward on Wednesday February 20, 2008 @04:03AM (#22485290)
    Yeah, it comes with "%30 MORE!" now.
  • by oz1cz (535384) on Wednesday February 20, 2008 @04:04AM (#22485300)
    Obesity is everywhere.
  • by Aaron Isotton (958761) on Wednesday February 20, 2008 @04:05AM (#22485302)
    Wikipedia says it's only 1000 light years thick.
    • Re: (Score:3, Insightful)

      by timmarhy (659436)
      that only confirms that wikipedia is not a reliable source.
      • by rucs_hack (784150) on Wednesday February 20, 2008 @04:13AM (#22485358)
        But, but, Voyager only had to cross 70,000 light years to get home....

        I mean, you're going to be saying Voyager wasn't real next...

        As if..
      • by I confirm I'm not a (720413) on Wednesday February 20, 2008 @04:35AM (#22485448) Journal

        To be fair to Wikipedia, they cite their source [wikipedia.org] for that claim. And the source is...

        ...(drumroll!)...

        NASA [nasa.gov]

        • What I find disturbing is the fact that a number is this widely off and no one discovered it for such a long time! I can imagine deviation by x % or less where x

          The split of Humans from the Apes pushed back by another 6 to 7 million years earlier than previously thought based on molecular genetics. The difference from the earlier estimate of around 5 to 6 million years is therefore over 100%
          http://www.news24.com/News24/Technology/News/0,,2-13-1443_2169361,00.html [news24.com]
          • by uhlume (597871) on Wednesday February 20, 2008 @06:44AM (#22486004) Homepage
            How is this modded "insightful"? Scientific models and methods improve, often building upon earlier models and methods. This isn't an indication of incompetence or malfeasance in the earlier science; it just means that we're getting better at it.

            Additionally, the revised estimate of the point of divergence of humans from primates as a result of newly-discovered fossil evidence isn't even remotely relevant to a case in which existing data has been re-interpreted to form a new conclusion.
            • by ta bu shi da yu (687699) * on Wednesday February 20, 2008 @08:26AM (#22486620) Homepage
              I'd say it's insightful because a. there are a lot of scientists interested in this sort of thing, and b. the calculation has been around for quite some time with noone challenging it.

              I thought scientists were meant to challenge conventional wisdom? The parent poster is only saying that in his/her opinion it took far too long for this one to be tested again.
              • by gfxguy (98788) on Wednesday February 20, 2008 @10:14AM (#22487394)
                It's what happens when one guy does a calculation and everybody else cites it... then it becomes "consensus."
                • Re: (Score:3, Insightful)

                  by uhlume (597871)
                  You have no evidence of such an occurrence in this case, and I'd challenge you to find conclusive and credible evidence of such a phenomenon in any other scientific consensus.

                  Boldly-worded Slashdot write-up and subsequent rush to Wikipedia notwithstanding, all we have here is a brief article in a little-known Australian paper, vaguely referencing an as-yet unpublished study by a group of astronomers who seem (it's hard to say anything without reference to the study itself) to have re-interpreted existing d
            • by pkphilip (6861) on Wednesday February 20, 2008 @09:42AM (#22487118)
              I agree that the nature of science is that we will definitely need to improve on our findings and get higher and higher levels of accuracy. That is to be expected.

              What I find worrying is the range of correction that needs to be applied and also the fact that the correction takes this long - especially considering that the group was able to arrive at a value which is *twice* the older value by just spending a little bit of time studying the data.

              The questions it raises are:

              1. How is it that the Milkyway was considered to be 6000 light years wide? When someone made this claim, wasn't the data ever rechecked by anyone? If someone with a spreadsheet can come up with this new value of 12000 light years just by spending a few hours studying it, why was it not done earlier? What happened to peer-review - was it ever conducted? If this isn't an indication of incompetence at some level among a few people involved in setting this value, what is?

              2. Scientific findings will, no doubt, be modified as new things come to light. However, corrections are normally meant to be just a few % off the initial value. 100% change is not an improvement - it means that the initial value was astoundingly and absolutely wrong. What is staggering about this is the fact that the new value was not calculated based on any *new* finding - but rather it was found just by recalculating based on the *already* existing data.

              3. What implications does this have on other findings?

              My example about the dating of primate and human evolution was to prove that these type of huge "corrections" have occured even in other scientific fields as well. So what we know to be absolutely true today, can be completely off tomorrow.
              • by zenyu (248067) on Wednesday February 20, 2008 @12:09PM (#22489014)
                My example about the dating of primate and human evolution was to prove that these type of huge "corrections" have occured even in other scientific fields as well. So what we know to be absolutely true today, can be completely off tomorrow.

                Scientists never know anything to be "absolutely true". Absolute truth is the domain of charlatans, liars and cheats.

                When geology started scientists proved that certain rocks in England were "millions of years old!", and postulated based on that that the earth might be "hundreds of millions of years old!". But those numbers seem quaint and even silly today. As new rocks were discovered we soon learned that they were billions of years old, and when we learned about plate tectonics we realized the Earth could be older than the oldest rocks we could find. Our guess as to what the milkyway even looks like are based on looking at other galaxies and then seeing similar structures in our own local neighborhood. We can't actually look at it like we look at other galaxies. We are inside of it; close by stars and dust obscure our view, and our vantage point is that of someone looking at a plane from the side.

                What we can see are 'standard candles', that is stars emitting light within a certain range based on our knowledge of nuclear reactions and our ability to calculate apparent mass and composition. This rests on nuclear reaction theory for stars of large mass that we can not test as easily as we can test say simple nuclear decay, and it also rests on a number of approximations for the amount of dust vs "dark matter" in the intervening space (once you know how bright the star is at it's surface, you then base it's distance from you on how bright it appears to you on earth; the stuff in between matters). Terms like "dark matter" and "dark energy" should be hints that we can be off by several magnitudes. If one star is somewhere between 5,000 and 10,000 light years away, while it sounds like a huge difference, the same approximations can tell us that another star is between 5 and 10 light years away.

                To put this in perspective, does it really matter if homo split off from ape 1 or 2 or 4 million years ago. Or, whether modern man is 50, 100, or 200 thousand years old? Even what happened in your day yesterday is not completely known to you. You have forgotten most of it, and what you do remember is colored by your dreams last night and your mind's ability to integrate it into what has happened before. But you'll make do with your imperfect knowledge of the day, this month you'll have an idea of how warm it was based on the weather this year + the fact that you don't remember it being an unseasonable day, and ten years from now you'll have an idea based on the season, and ten thousand years from now, people reading your description of your day will have an idea of the weather based on the season and climate. All are less accurate than if I had asked you yesterday how warm it was, but so long as you understand the data and it's approximate accuracy it is still useful. It's useful to have an idea of how long ago ape split off from man vs when modern man split off from other human species, but the day the month and the year isn't important when you're dealing with large numbers like this. The order of magnitude is all you need for any useful work. The processes probably took many years anyway. Except in the laboratory, speciation doesn't happen overnight...
          • by ta bu shi da yu (687699) * on Wednesday February 20, 2008 @07:40AM (#22486354) Homepage
            Given that Excel is so notoriously inaccurate when doing floating point calculations, I'd be interested if someone else did this in another application. I wonder if they would get the same result.
          • by boot_img (610085) on Wednesday February 20, 2008 @08:43AM (#22486720)
            ... is shown right here on this slashdot discussion.

            I am an astronomer, so first some background: The Milky way has several components: young stars, old stars, dust and various components of gas. They all have different thicknesses. There is no single "thickness". One of these components (warm ionized gas) has been measured to have a thickness larger than expected. This measurement has not been confirmed by others, nor (I think) published yet.

            Despite this complexity, this discussion thread is awash with arguments, confusion, wild speculation, suggestions that dark matter might be wrong etc. etc. OK, fine, this is slashdot, that's what slashdot is for.

            But the same people (presumably) have also rushed off to edit Wikipedia! (I see a half dozen edits this morning, to add in the "new" thickness.) That's the part that I find incredible. And people really take Wikipedia seriously?

            • by greginnj (891863) on Wednesday February 20, 2008 @09:56AM (#22487246) Homepage Journal

              But the same people (presumably) have also rushed off to edit Wikipedia! (I see a half dozen edits this morning, to add in the "new" thickness.) That's the part that I find incredible. And people really take Wikipedia seriously?
              You're right. God forbid some stupid fucking amateurs should be so passionately interested in your field that they would do something so counterproductive to your ivory-tower efforts as ... editing a Wikipedia article. It's not like they're part of the public that becomes more or less willing support funding for NSF or NASA grants, for instance. You should be able to get by on royal patronage just fine, without being troubled by the noise generated by hoi polloi.
              • by boot_img (610085) on Wednesday February 20, 2008 @10:37AM (#22487676)

                God forbid some stupid fucking amateurs should be so passionately interested in your field that they would do something so counterproductive to your ivory-tower efforts as ... editing a Wikipedia article

                I guess I should clarify. I have no problem with amateurs editing Wikipedia. But I do have problems with, as you say, stupid, fucking amateurs editing Wikipedia.

                For example, at the moment Wikipedia says:

                The disk of the Milky Way galaxy is approximately 100,000 light years in diameter, and is believed to be about 1,000 light years thick (average thickness),[8] with the center bulge's thickness recently discovered by University of Sydney researchers to be about 12,000 light years, contrary to the previously thought 6,000.[9]

                This is not correct. The Wikipedia editors have decided somehow that the 12,000 light year measurement refers to the center of the Milky Way (even though it does not state this anywhere in the U Sydney Press Release). As I said above, the 12,000 light year measurement refers not to a location but to a component, the Warm Ionised Medium or WIM.

                My point is simply that the quality of Wikipedia is only as good as the effort that editors make to understand a subject and edit appropriately.

                • by greginnj (891863) on Wednesday February 20, 2008 @11:02AM (#22487992) Homepage Journal
                  I'm perfectly willing to concede that you have expertise on this subject. Since you complain that

                  the quality of Wikipedia is only as good as the effort that editors make to understand a subject and edit appropriately.
                  why don't you become an editor and help it along? It's not hard at all. When talking about Wikipedia editors, there is no "them". Rather than telling Slashdot that Wikipedia could be better, you could be ... making Wikipedia better. If you put in appropriate footnotes and a clear explanation, especially once today's media frenzy dies down, you'll be lighting a candle rather than cursing the darkness. [Full disclosure, and odd coincidence: a while back, I made a minor edit for clarity to the article on "peculiar velocity" [wikipedia.org]. The article is still a stub -- feel free to check it out and improve it [wikipedia.org]. ]

                  I can easily understand that talking about 'how thick the galaxy is' is a lot like the 'is Pluto a planet' dispute -- it's just shorthand for more complex issues that you could elucidate. For example -- you could provide a brief paragraph describing the controversy, and how different elements lead to different measures of a galaxy's thickness, and give those measures. You'd be, you know, educating. If you both care enough and know enough about a subject to be bothered by the Wikipedia article, that's a sign you should be improving it.
            • by mysticgoat (582871) on Wednesday February 20, 2008 @10:58AM (#22487932) Homepage Journal

              You bet I take Wikipedia seriously.

              It is the largest and broadest source of information that has ever been available, any where, any time. It gives access to any of 2.25 million articles at incredible speed: it takes many times longer to phrase the Google query that identifies the relevant article than it does to fetch the text.

              Are the contents accurate?

              That's the wrong question.

              Are the contents useful?

              You bet they are, if you understand the context and know how to critically assess what you read. As with any encyclopedia, the most valuable parts of the articles are the references and citations to other works. Through those, a discerning reader can learn the major features of an unfamiliar field. Additionally, the Wikipedia article itself is a pretty good indicator of what the well informed non-expert believes he knows about any field. This is important: it wasn't so long ago that expensive surveys were the only tools for assessing lay knowledge about a field.

              Wikipedia is not authoritative. That does not diminish its value. For various reasons no encyclopedic collection is an authority on any subject (other than itself, and even that is often time-limited).

        • Re: (Score:3, Informative)

          by Anonymous Coward
          Leave it to wikipedia to cite as a source a NASA edutainment page aimed at grade schoolers.

          What the "source" doesn't mention (because it's not meant to give an in depth answer) is that the galaxy is ~1000ly thick on average. It is quite a bit thinner along its edge, and quite a bit thicker in the core.
        • by Misanthrope (49269) on Wednesday February 20, 2008 @05:32AM (#22485694)

                  Whenever life gets you down, Mrs. Brown,
                  And things seem hard or tough,
                  And people are stupid, obnoxious or daft,
                  And you feel that you've had quite eno-o-o-o-o-ough...

                  Just remember that you're standing on a planet that's evolving
                  And revolving at nine hundred miles an hour,
                  That's orbiting at nineteen miles a second, so it's reckoned,
                  A sun that is the source of all our power.
                  The sun and you and me and all the stars that we can see
                  Are moving at a million miles a day
                  In an outer spiral arm, at forty thousand miles an hour,
                  Of the galaxy we call the "Milky Way".

                  Our galaxy itself contains a hundred billion stars.
                  It's a hundred thousand light years side to side.
                  It bulges in the middle, sixteen thousand light years thick,
                  But out by us, it's just three thousand light years wide.
                  We're thirty thousand light years from galactic central point.
                  We go 'round every two hundred million years,
                  And our galaxy is only one of millions of billions
                  In this amazing and expanding universe.

                  (Animated calliope interlude)

                  The universe itself keeps on expanding and expanding
                  In all of the directions it can whizz
                  As fast as it can go, at the speed of light, you know,
                  Twelve million miles a minute, and that's the fastest speed there is.
                  So remember, when you're feeling very small and insecure,
                  How amazingly unlikely is your birth,
                  And pray that there's intelligent life somewhere up in space,
                  'Cause there's bugger all down here on Earth.
        • by uhlume (597871)
          The NASA source doesn't specify at what radius the thickness is measured, leading me to believe that the "1000 light years" figure references an average, or representative, thickness. According to the summary (although curiously unmentioned in TFA) this new discovery seems to pertain specifically to the Milky Way's thickness at the Galactic core, where it is substantially thicker than at points located further down the arms (as illustrated in this side view [usra.edu]).
        • Re: (Score:3, Funny)

          by Jesus_666 (702802)
          Oh, that's already common knowledge - when NASA calculated the size of the galaxy, the reference data was in parsecs and the NASA engineer assumed that it was in terarods. Thus they're roughly 5/6 off mark.
      • Re: (Score:2, Insightful)

        by TapeCutter (624760)
        People who depend on a single source are unreliable.
      • by Jugalator (259273) on Wednesday February 20, 2008 @05:09AM (#22485582) Journal

        that only confirms that wikipedia is not a reliable source.
        This argument is getting sort of tiresome to me. In well written Wikipedia articles, key facts are often referenced today. This then becomes a blanket argument against Wikipedia as a whole, without caring for whether the information was well referenced or not. Often, it is. Sure, often it's not too, but IMHO, one need to check that out first.

        This time, you've already received your answer to why Wikipedia had this information, and it's in fact not a long time ago I've had to do the same.

        So, please guys, before you bash Wikipedia, check if there's a good reason to the discrepancy of the information. Surprisingly often, especially in articles receiving good attention like the one for our galaxy, there is.
        • by Eivind (15695) <eivindorama@gmail.com> on Wednesday February 20, 2008 @05:43AM (#22485746) Homepage
          Technically, Wikipedia should never claim any spesific thing. They don't really have an opinion as such on the size of the MW or anything else. Yeah, I know, the article says "The Milky-Way is so-and-so big". But that should really be read as:

          "Our sources, given under this article, claims that the Milky-Way is so-and-so big" One could write it like that, but it'd become tiresome real quick.

          That information is by nessecity only at best as good as the sources.

          Besides; that's the way reality works in general. When somebody claims some fact it ALWAYS means that based on the sources that that person choose to believe (be it his own eyes or a scientific paper, or Fox-news) says so.
      • by wall0159 (881759)
        ...and which article will be sooner updated to reflect our new understanding - Wikipedia, or Britannica?

        Hell, Wikipedia will probably be updated sooner than NASA!
    • by kryten_nl (863119) on Wednesday February 20, 2008 @04:12AM (#22485346)
      Quick, e-mail them! They'll have to retract their article.
    • by supermari0 (1238518) on Wednesday February 20, 2008 @04:27AM (#22485424)
      holy astronomy! to the wikipedia edit page... dadadada dadadada!
    • Re: (Score:3, Insightful)

      by Atario (673917)
      Not anymore! Hee hee!
    • My wikipedia says the thickness is 12,000 light years.
  • 2x bigger (Score:3, Insightful)

    by Feef Lovecraft (1231264) <feeferscatNO@SPAMgmail.com> on Wednesday February 20, 2008 @04:06AM (#22485308) Homepage
    So until now everyone was just measuring the radius of the Milky Way?
  • A good reminder (Score:5, Interesting)

    by A beautiful mind (821714) on Wednesday February 20, 2008 @04:06AM (#22485314)
    This is a good reminder how you're supposed to dig down to the raw data and validate that. I remember reading in one of Richard Feynman's books about a similar case, some conclusion or data appeared well supported, because a lot of the research papers were supportive of the idea, but it turned out that they derived what they said based on a single source.

    The case here is similar, it's a good reminder how science is about data, validation and facts not about authority. You're supposed to check your data, check your facts and try to avoid making implicit assumptions.
    • Re: (Score:3, Insightful)

      by bandersnatch (176074)
      because like the internet is like TOTALLY a definitave source mkay?
    • Re: (Score:3, Interesting)

      That reminds me of a famous scientist who was mentioning HIV in an article he was writing, and wanted to cite the original source where it was first discovered and published that HIV caused AIDS. He couldn't find it. No one else he talked to could either. It turns out that what is a common assumption (and perhaps true) has never actually been verified and published.
      • file under pants (Score:4, Interesting)

        by tinkerton (199273) on Wednesday February 20, 2008 @04:46AM (#22485490)
        That famous scientist may have allowed himself to get carried away a bit. What it means is that there was no clean breakthrough article. Rather, evidence gradually accumulated. What it does not mean is that the connexion is "perhaps true", certainly not in the current stage where effective medicines exist.

        On the other hand it's good practice to have roundup articles that go over the evidence.
      • by martin-boundary (547041) on Wednesday February 20, 2008 @05:02AM (#22485550)
        This reminds me of a famous politician who was mentioning WMD in a speech he was having written, and wanted to cite the original source where they were discovered in a certain country or other. He couldn't find it. No one else he talked to could either. It turns out that what was a common assumption (and turned out false) had never actually been verified. So he winged it.
      • by sholden (12227)
        To verify it you would have to have a control group and then the group that you infect with HIV and see if they get AIDS more... Good luck getting that past the ethics board.

        There is Blattner et al in '93 looking at three lab workers who were exposed to HIV, http://gateway.nlm.nih.gov/MeetingAbstracts/102203749.html [nih.gov]

        And of course Schechter et al in '93, which looked at 715 homosexual men, with about a 50/50 split of HIV positive and HIV negative. All 136 who ended up with AIDS during the study were HIV posit
      • Re:A good reminder (Score:4, Insightful)

        by TapeCutter (624760) on Wednesday February 20, 2008 @05:24AM (#22485662) Journal
        The other reply is correct. It's not that everyone just assumed it's origin it's that everyone was uncertain about the origin. There was a hell of a lot of evidence collected for the CDC, WHO and others. Science is designed like that, nobody is ever 100% certain about anything.

        Some religious and political groups (where many claim/demand proof) use this systematic uncertainty to justify their particular perversions of common decency when science presents them with inconvienient evidence. The search for the origin of aids was a good example.

        Nobody is immune because nobody can keep up with everything. The comments on slashdot demonstrate that every day. Over the last 7-8yrs there has been a magnificent debate on slashdot over global warming. What once was marked troll is now insightfull, if nothing else I think most of the regulars (including me) know more about the science behind it than they did a few years ago.
    • by Kelz (611260)
      And lets hope that not too much research is completely screwed due to a change in a constant (though what experiments would need to take into account the diameter of the galaxy I do not know).
    • by Anonymous Coward
      Well, if we're expecting that the universe is actually 75 to 95 percent dark matter based on the
      SAME KIND OF FLAWED DATA, perhaps we are underestimating the amount of matter we actually CAN see.

      I always wondered how exactly they determined how much matter was in the universe, indirect evidence or not.
      Seems like there may be few assumptive leaps there, upon which we build our entire cosmological understanding.

      If the 'missing' matter is actually regular matter that we haven't found, or have found and discount
    • "...it's a good reminder how science is about data, validation and facts not about authority. You're supposed to check your data, check your facts and try to avoid making implicit assumptions."

      ...and then in your twilight years some smart-arse with a spreadsheet takes all the fun out of polishing your nobel.
  • by The Ancients (626689) on Wednesday February 20, 2008 @04:07AM (#22485320) Homepage
    So I read the article (yeah, yeah - I know...I was bored) and I hope the spreadsheet software used wasn't Excel - we all know how well that counts.
  • by Thanshin (1188877) on Wednesday February 20, 2008 @04:13AM (#22485360)
    Is there any physical effect where a galaxy ends? Or are we just talking about an imaginary limit.

    How hard is it to map the galaxy? If we don't know where the stars are, we can't know the size. If we know, we don't need it; we can describe the actual, real, shape.

    Where's the flaw in my logic? (I hope it's in the part about the limit being imaginary, I like limits in Space like the heliosphere)
    • Re: (Score:3, Informative)

      by timnbron (1166139)
      They're measuring the sea of electrons between the stars, which they assume stops at the 'edge' of the galaxy.

      FTA:
      "As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down. ... If you know the distance to the pulsar accurately, then you can work out how dense the WIM is and where it stops - in other words where the Galaxy's edge is.
      • by Thanshin (1188877)
        Ok. So there's actually a physical limit: the border between the intergalactic medium (IGM) and the interstellar medium (ISM).

        Pretty, pretty Universe.
    • by SnowZero (92219) on Wednesday February 20, 2008 @04:51AM (#22485510)

      Is there any physical effect where a galaxy ends? Or are we just talking about an imaginary limit.
      Yes, you pass a sign that says "Now leaving Milky Way galaxy, pop 13.167B". That is soon followed by a sign reading "Ejected star crossing, next 200,000 light years."

      How hard is it to map the galaxy?
      It's pretty easy actually; We draw the Earth, the rest of the solar system, a few constellations, and a whole lot of "here be dragons[1] (maybe)".

      Where's the flaw in my logic?
      Asking a serious question on slashdot. At night. Clearly.

      [1] Now known to consist of dark matter and dark energy, which is why you can't see them.
    • by Siener (139990) on Wednesday February 20, 2008 @06:08AM (#22485852) Homepage

      How hard is it to map the galaxy? If we don't know where the stars are, we can't know the size. If we know, we don't need it; we can describe the actual, real, shape.

      It's pretty hard to measure the size and shape of the Milky Way simply because we are stuck in the middle of it. Measuring the size and shape of far away galaxies is a lot easier because we have a better view. Our galaxy is a flat disk with spiral arms where we are in one of those arms - the overall structure is very hard to measure from that perspective. To complicate things further there is quite a lot if interstellar dust that messes up our view in certain directions.

      As an analogy - imagine being stuck in a traffic jam. Figuring out the extent of it is very hard from the view you get from your car. A helicopter in the sky has no problems though.
  • skeptical (Score:2, Interesting)

    by timmarhy (659436)
    have they checked their freely available sources they found on the internets? seriously i'm dubious of everything claiming to use a spread sheet and/or internet sources these days.
  • 'cause I think I'm supposed to know but I don't, but how does the tag "montypythonwaswrong" relate to this story?
    • by bersl2 (689221)
      I can't remember the exact number, but there was a song in The Meaning of Life that mentioned the diameter of the galaxy. "The Galaxy Song" I think is what the song is titled.
      • There was a song in The Meaning of Life that mentioned the diameter of the galaxy. "The Galaxy Song" I think is what the song is titled.

        Yes, the "Galaxy Song". Look here now [geocities.com] for the lyrics before GeoCities melts. Second verse: "It bulges in the middle, sixteen thousand light years thick." etc.

        • Re: (Score:2, Informative)

          by Anonymous Coward
          As a public service to the Slashdot community I'm going to blatantly violate copywrite and post the lyrics here so we can all see them after geocities melts down

          Galaxy Song

          Spoken: Whenever life gets you down Mrs. Brown,
          And things seem hard or tough,
          And people are stupid, obnoxious or daft
          And you feel that you've had quite enough...

          Just remember that you're standing on a planet that's evolving
          And revolving at nine hundred miles an hour,
          That's orbiting at nineteen miles a second, so it's reckoned,
          A sun that i
  • It's only ~ 1.4426 times as big as we thought in log scale...
  • by backslashdot (95548) on Wednesday February 20, 2008 @04:41AM (#22485468)
    Now you guys tell me!

    What the Fudge man, I have been eating Snickers all this time thinking I'm getting more chocolate! Now I find this out?
  • by Trogre (513942) on Wednesday February 20, 2008 @04:43AM (#22485476) Homepage
    What we're seeing now is middle age spread.

  • by jsse (254124) on Wednesday February 20, 2008 @05:02AM (#22485552) Homepage Journal
    Use something a layman could understand OK?

    Say, how many Library of Congress, or elephants, have we got here?
  • by dltaylor (7510) on Wednesday February 20, 2008 @05:17AM (#22485628)
    The spiral arms are thicker than we've been assuming. Does that mean that there are more stars and gas/dust clouds in the greater volume? If there are more, then the mass of the galaxy is higher, and with the relativistic adjustment recently adopted, there's less need for a "dark halo", or, at least, less of one required to balance the velocity of the outer stars. OTOH, if there's the same amount, then the density is less, which throws off the very measurement technique that they're using to derive the new thickness, since the less-dense interstellar medium will have less effect on the two wavelengths (yeah, I read the article).

    Anyone know of an online resource for the American Astronomical Society papers? I'd like to see what, if anything, they say about the density values for the WIM.
  • by Linker3000 (626634) on Wednesday February 20, 2008 @05:19AM (#22485640) Journal
    ...We are told that the sun's light takes approx 8 minutes to reach us, but now we know that the distance involved is twice as much so therefore the speed of light must be approximately double what we thought! ...if the moon is twice as far away as previously thought, how come astronauts have landed successfully - in theory, they should get 'there' and be in the middle of nowhere ...UNLESS, of course they never went....AH HA!!!

  • by delibes (303485) on Wednesday February 20, 2008 @05:37AM (#22485722)
    "Our galaxy itself contains a hundred billion stars. It's a hundred thousand light years side to side. It bulges in the middle, sixteen thousand light years thick, But out by us, it's just three thousand light years wide."
  • Mmmm. Double-sized Milky Way. aaaaagggggcccchhhh (drools).
  • by syousef (465911) on Wednesday February 20, 2008 @05:43AM (#22485752) Journal
    From TFA with commentary:

    Proving not all science requires big, expensive apparatus, Professor Gaensler and colleagues...downloaded data from the internet

    No, this actually proves that you can reuse data gathered with large expensive apparatus. There's a difference. They couldn't have done this without expensive infrastructure that just happened to cost them nothing (or close to nothing) - ie. The original instruments and the Internet.

    The University of Sydney team's analysis differs from previous calculations because they were more discerning with their data selection. "We used data from pulsars: stars that flash with a regular pulse," Professor Gaensler explains. "As light from these pulsars travels to us, it interacts with electrons scattered between the stars (the Warm Ionised Medium, or WIM), which slows the light down.

    Well now wouldn't you want to explore why the data differs so much, before declaring your answer to be the correct one just because you verified your calculations are correct?

    My first thought is: Did they use some standard or average value for the density of the WIM? Could the discrepancy be because the WIM itself is not uniform through the thickness of the galaxy/

    This is definitely an interesting result and worth following up but rather than declare victory the real question is why is there such a large discrepancy with other data?

    • by schwanerhill (135840) on Wednesday February 20, 2008 @11:16AM (#22488194)

      The pulsar data they downloaded from the internet largely did use big, expensive instruments—this work is a new, improved analysis of a large sample of already-published data from many sources.

      They did not use the canonical space-averaged electron density for the WIM (0.03 cm-3); they used pulsars with independent distance measurements*. What's different about their work from previous estimates of the scale height of the WIM is that they did not use pulsars with any of several other distance measurement techniques that are less reliable. In particular, one of the commonly used distance measurement techniques uses absorption due to neutral hydrogen in the plane of the Milky Way. However, the neutral hydrogen (cold neutral medium, CNM) disk is considerably thinner than the WIM disk (scale height of 100–250 pc, depending upon whom you ask, versus 1000 (the old result)–1800 (their new result) pc for the WIM), so that technique only works at all well for pulsars in the plane (and is still model-dependent even then), which makes it a biased sample for measuring the height of the Milky Way's disk.

      These authors also limits themselves to galactic latitudes |b| > 40 degrees, which means that they're sampling a relatively local cylinder about the Sun. Therefore, their sample isn't contaminated by spiral arms or many classical H II regions [wikipedia.org] (gas ionized by hot, massive stars), which will change the result.

      This result is a fairly dramatic revision of the scale height of this phase of the interstellar medium and, consequently, the weight of the medium. (In fact, it's the phase I make my living studying, so it's very important to me!) However, this does not have any bearing on the scale height of the stars (which contain 85% of the mass in the Galaxy) or the neutral hydrogen. It also doesn't change the total amount of ionized gas in the WIM. (That column density is measured very accurately by pulsar dispersion.)

      The WIM is certainly not uniform throughout the Galaxy. It is a turbulent medium with varying densities, and it only fills ~20% (that number is highly uncertain, to a factor of two or more, I would say) of the volume within the 1000–1800 pc high disk. However, particularly over the path lengths the more distant pulsars sample, those local differences should be pretty well averaged out.

      The discrepancy with previous work is largely due to a tremendous amount of progress in recent years measuring parallax distances to pulsars, largely using very long baseline interferometry [wikipedia.org]. Distance measurements in astronomy are notoriously difficult, and improvements will continue for years to come.

      * They relied only upon distance measurements determined in one of two ways: parallax [wikipedia.org] (the only direct distance measurement method in astronomy, useful for relatively near pulsars—out to about 1000 pc=3000 ly, with decreasing accuracy further away) and association with globular clusters. Globular clusters contain thousands of stars that were formed at about the same time and have the same heavy element content, so their distance can be determined based on standard, well-known stellar evolution models and a color-magnitude diagram. These two distance measurements are about as accurate as a pulsar distance measurement will get in the foreseeable future, although particularly the parallax distances will continue to improve both in quantity and quality.

  • It bulges in the middle, sixteen thousand light years thick
    Ok, so they were 4,000 light years out, but that's better than 6,000.
  • Define "edge" (Score:3, Insightful)

    by Dan100 (1003855) on Wednesday February 20, 2008 @06:03AM (#22485826) Homepage
    To measure the thickness of something, you need to know where it ends. The Milky Way isn't a solid object, so there must be some arbitary definition of the "edge" where the average density drops below a certain value.

    Perhaps the differences in quoted thicknesses are the result of different definitions of the edge?

  • Actual paper? (Score:5, Interesting)

    by N7DR (536428) on Wednesday February 20, 2008 @06:09AM (#22485856) Homepage
    Does anyone know where the actual paper can be found? TFA is just a news release for the popular press. Going to the list of publications for the author of the study (http://www.physics.usyd.edu.au/~bmg/papers/) doesn't list anything that looks like it's the paper on which the news release is based.

    TFA says: "The team's results were presented in January this year at the 211th meeting of the American Astronomical Society in Austin, Texas." but there's no indication of where the results have actually been published in a peer-reviewed journal so that one could read the paper for oneself. I looked on the AAS site and couldn't find anything there either. So, pending access to a detailed published per-reviewed account of their work, I'm reserving judgement as to how valid the claim is.

    • Re: (Score:3, Informative)

      by schwanerhill (135840)
      The research was presented in a poster at the AAS meeting. I have a copy of the poster on my desk, but it's not, to my knowledge, in a generally available place, and no paper has appeared (yet). It's a tad unusual for a press release to be put out with no accompanying published paper.

      The abstract is available [harvard.edu]. However, as is typical for the AAS, the abstract has to be submitted in October for the January meeting and therefore doesn't have the actual result that's in the poster.
  • My first thought was it referred to the choccy bar 'Milky Way' and got all excited.
  • by catdevnull (531283) on Wednesday February 20, 2008 @11:39AM (#22488550)
    ***GUARANTEED increase your galaxy by 6,000 light years***
    thick and sturdy clusters. ladies love dark matter. hawking beautiful einstein copernicus keppler cassini
    jplab buzz lightyear wormhole

    [sorry--I couldn't resist]
  • Damn it! (Score:3, Funny)

    by fahrbot-bot (874524) on Wednesday February 20, 2008 @02:47PM (#22491586)
    Now I have to pack an extra suitcase.

It is better to give than to lend, and it costs about the same.

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