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Science

Black Holes...Pink? 55

Posted by Hemos from the i'd-like-mine-ty-died dept.
st. augustine writes "Australian astronomers have discovered that some black holes are actually pink. Here's a Wired article, and here's the Australians themselves. I was more excited before I found out they were already expecting the black holes to be blue. "
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Black Holes...Pink? More

Black Holes...Pink?

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  • Re:Hawking Radiation (Score:1)

    by Anonymous Coward
    No, it's not Hawking radiation (as I tried to point out in the earlier "Clarifications" comment). Hawking radiation just wouldn't be intense enough, it gets weaker for larger bodies (like huge quasars). It wouldn't be pink either, but some pure blackbody temperature.

  • Slashdot denizens == Groundhogs (Score:1)

    by Anonymous Coward
    I dread the posting of items astronomical on Slashdot. The (*attempting to be judicious*) ignorance and jeering, peasant-like-tone, calls to question and account the elder statement that hackers match in their interests the pursuit of *science fiction*, an integral aspect of which is astronomy or at the least, astrophysics. But the queries here encoded? Abominable! I hail my fellow Anonymous Cowards (Scores 5 and 4) who anticipated the spate of questions and answered them.
    All here, 't'would seem, hail Star Trek and Star Wars... but sit in discussing actual phenomena and knowledge of even our own mere star system like ignorant old European men discussing some 19th century war!
    To answer a pair of (almost unasked) queries -
    The speed of light is c. 299,792.4562 km/s. Rounding to 3EX is useful for rough estimates, but when one wishes to assess the highly dependent values such as the distance to a given Cepheid variable, such rounding *would not* occur!
    How long, then, is a light year? This, too, may depend on the astronomer's hewing to his or her art. The civil year is measured as being 365.0 days of 24 hours - but the sidereal year (the actual momentum of the planet) measures as 365.26 rotations, each 23 hours, 56 minutes, 4 seconds in length. Multiply the value of C by the sidereal to determine a light year, if you wish.
    A parsec is 3.2616 light years in length... it derives from the measure of parallax on the dome of the sky, helping to measure proper motion and the like. Barnard's Star, a dim red dwarf, was discovered and made known as remarkable for it's proper motion, greatest of any star! It is only 5.2 light years distant. Doubtless many such red dwarfs arc nearby in this our section of the galactic disk, hidden by their radiative obscurity.
    I despair for our culture. We seem to be regressing toward the primitive expansion of old human memes within a terrestrially advanced framework rather than rising to the sublime. But, what may I expect? Observe those men who walked on Luna and saw the glories of our world in the 1960s - they could hardly be named pioneers or visionaries, or revolutionaries! Only one of them was a scientist (the geologist of Apollo 17). John Glenn, *snort* - a politician, and most actually believe that he walked the Lunar regolith. We are surrounded by our wondrous networking technology (and yet arguing over ludicrous obvious issues such as whether our operating systems should be open engineering works), but how many of you feel that the future the old stories promised has come? Belter cultures, Lunar cities, Martian wars of independence? How prefer you instead, "Congress would like to pass the US Space Shuttle to business and fly it until the 2020s"?
    As I posted this, I was notified that the International Space Station was passing overhead. Due to my presence in the city and it's low altitude, I was unable to see it on this pass. But I observe it when I may! A strange sight, to see that star-like object moving through the sky so quickly, still stranger to *know what it is*... but how many of you look up even to the few works our hands have acheived?
  • Posted by AnnoyingMouseCoward:

    Essentially, I have to agree with the general point of your posting. People these days spend too much time reading Sci-Fi and not enough time actually reading about science.

    Sci-Fi is not about science, it's about our own terrestrial obsessions projected onto a bunch of aliens.

    As a point in case, just consider the amount of Sci-Fi which is set here in the solar-system versus the amount which is set on *habitable* planets around other stars.

    Having discovered that there are no easy frontiers here in our own backyard, we ignore the possibilities and look elsewhere, in spite of the enourmous resources in terms of material and energy that we could tap.

    In short, most Sci-Fi looks at the past. It's an attempt to re-enact the process of European colonialism on a larger scale. Because of that, few people are interested in anything that isn't a habitable planet.

    Still, things are gradually changing. The terra-forming of Mars is gradually coming into the conceptual realm of the general public and it may simply be a matter of time before we re-adjust our perspective away from terrestrial obsessions. Unfortunatly for me, it's not likely to be during my lifetime though.
  • I mean come on! This is been a recurent posting on usenet for years... Black holes being pink... because they are made of spam :-) don't you find this funny? have you actually followed the link [frivolity.com]?

    It's not offensive or anything, it's just humour

    Maybe I don't get it....

    ---

  • To sum-up a longer [frivolity.com] proof, there is no such a thing as a black hole, because black holes are actually made of spam, and spam is pink!

    ---

  • To my knowledge, relativity and qm have not been merged, that is the whole point of all the work that has been done on grand unified theories (guts).

    You wouldn't happen to be from Fresno would you? People from Fresno might be able to confirm your theory. (Now that's an obscure reference, anyone get it? ;)

  • The same precise conversion is done in measuring all their distances.
  • Then I wanted to sneak those two zeros in there.
    oops.
    thanks.
  • I thought at first, oh, they're just using a British billion (a million million) but that would have put them off by a factor of 10.

    Good question, and even more interesting that the same calculation is repeated in all their distance measurements.
  • Hmm, yes, it's only a theory, probably the best but have they had any major breakthroughs with the observational data in the last few years?
    I'm just interested to know.
  • Why do they assume that quasars and black holes are one and the same thing? I know there are theories about the "power source" of quasars being not larger than a certain size because their luminosity varies with a certain period, so the speed of light limits the size etc.
    In the last few years, what new findings have their been?
  • Yes, and in Disney, mice can talk.
    ;-)

  • When I said about and approximate, I mean +/- a much smaller delta than a factor of three. eg. The speed of light in a vacuum is 3e8 m/s +/- 1e7 m/s (a far cry from saying its between 1e8 and 1e9). Same for the 9.5e15 (+/- 1e14). It's called significant figures.

    The issue is that they used the exact same (incorrect) conversion for each place that they mentioned a light-year to kilometer conversion.

    Now, on the other hand, if I were approximating with logarithms, and took an exponent (either that, or I looked at a slide rule with a severe astigmatism), I could expect a factor of 3 error very easily, because that's a linear error of only 0.5 in the log10 domain.

    --Joe

    --

  • When I took all of my science courses, I was taught that 1 light-year == the distance light travels in one year in a vacuum. In the article, they mention the following:

    This quasar is about one billion light-years away (30,000,000,000,000,000,000,000 kilometres).

    In other words, one billion light-years is 3e25 meters. Interpreting one billion as 1e9, this implies that one light year is 3e16 meters.

    Now, if I recall correctly, the speed of light in a vacuum is approximately 3e8 meters/second. There are approximately 3.16e7 seconds in a year (365.24 * 24 * 60 * 60). Multiplying these together gives me a light-year of about 9.5e15.

    So, is it just me, or are their light-years off by about a factor of 3?

    --Joe

    --
  • Actually, more like a factor of 1000.

    --
  • This was my thought.

    If the black hole is sucking in gas towards the viewer, it will appear to be blue (shorter wave length)

    If the direction of suck is away from the viewer, it ought to appear red (longer wave length).

    And if the acretion disk were viewed edge-on, one would see both red- and blue- shifted light.

    I'm no high-energy astrophysicist, but doesn't this explanation make sense?
  • Glad to be of service! Share and enjoy!
  • So is the "pinkness" the result of Hawking Radiation from the black holes? Steven Hawking (did I spell his name right?) predicted many years ago that black holes emmitted radiation - kind of combining gravatation theory with the Heisenberg Uncertainty Principle.

    I recall seeing a TV program in England about 1982/3 where Hawking said that if they ever actually found his radiation, he would get a Nobel Prize.

    Well, I am sure that these Australians would have thought of this (since Hawking Radiation is rather well known) and maybe it just isn't in the right frequency range.

    (P.S. that TV show had a 1 second shot of me crossing the street - I just happened to be in front of the camera when they were filming Trinity Street in Cambridge.)
  • Hmm. . .Pink, as I always understood, was a light, diffused red. Could we just be seeing frictional heating of surrounding gas clouds, diffused by the clouds beyond the heated zone ???

    Denser clouds would heat more by friction, pushing it from red-hot to yellow-hot to blue-hot. . .or would it ???

    As far as a doppler effect due to rotation, no. The effects of a receding edge would effectively be countered by the approaching edge. . .

  • I agree, but wouldn't much of the material being drawn toward the observer be located on the oposite side of the event horizon so as to be out of sight. It seams the net affect would be more of the visable acretion disk would be red shifted. Another question: Is the relative velocity of the acreting material with respect to the object great enough to be significant when compared to the expansion of the universe?

    Sorry, I should do some research, I'm not much of an astronomer yet...
  • oh sh-- just wait untill the rev jerry falwell hears about this...
  • Could the light be redshifted? Perhaps one side is orbiting away from us so fast it is redshifted to pink? But then you'd expect the opposite side to be blueshifted...is the telescope resolution high enough to see that?
  • Right. One side of the accretion disk is orbiting away from the earth so the light it emits is redshifted by the Doppler effect, and the other side is blueshifted. (The inner part of the accretion disk is falling into the black hole, but the velocity there is small in comparison with the velocity of rotation.) However, there is another, additional, redshift which is due to light losing energy as it escapes from the gravitational attraction of the black hole (or, what amounts to the same, to the time slowing effect in the neighborhood of the black hole). So on one side of the hole the Doppler shift and the gravitational shift add up and on the other side they compensate.

    Anyway, there are a lot of effects in play there: the expansion of the universe is a pretty large one. And, of course, we don't know what the initial wavelength of the emitted radiation was... So to say that the light is pink because it is redshifted is a pretty big simplification.
  • I still say we go with the Red Dwarf idea.

    Find 100 perfect suns in the right combination, make them all go nova, so all around the universe everybody can read....

    Enjoy Coke.

    And now after that happens the big novad stars will be a cute pink. What a beautiful universe.
  • For someone who acts so holier-than-thou, you should at least get your facts right.

    The year that we measure on the planet is 365.24 days (hence the leap year every 4 years). A sidreal year is actually 366.24 years . . .

    Just thought you might want to know. . .
  • It sort of makes sense. The only trouble is that black hole sucking is isotropic (the same in all directions). So, there will always be a component towards and away from the observer. In theory, if we could resolve the acretion disk (we cannot come even close for Quasars) we would see some blue shifted light and some red shifted light. . . but at those distances everything is so redshifted anyway (do to universe expansion) that it all looks red :-)
  • It is almost certain that Quasars are powered by black holes. That is what modern theory says, anyway, and it seems pretty valid.
  • How is it possible that the velocity of the jets exceeds c? It should never exceed c from _any_ reference frame.
  • "approximately 3e8 meters/second"
    "about 9.5e15"

    You said it, when your approximating all over the place, it's not suprising that you should be off by a factor of 3.
  • I guess it's just a matter of how you say it.

    The Earth, when viewed from space, rotates on its axis (about) 366.25 times by the time it goes around the Sun. We on Earth only see this as 365.25 days due to the fact that we are going around the Sun as well and one whole rotation is lost due to movement in it's orbit (this is much easier with pictures :-))

    Allright. Here is a better explanation (hopefully). There are 3.155815x10^7 seconds in a year. If we divide this time by the length of the sideral day, we get 366.25 . . . If we divide it by an Earth day (what we see here on Earth) we get 365.25 days. . .

    Like everything, it's a matter of perspective. . .
  • Well, technically some of the matter would be hidden by the event horizon, but the black hole is so tiny compared to the accretion disk that it doesn't really have an affect on the color. The main material that you have to look at in redshift/blueshift considerations is the material adjacent to the black hole, not the stuff in front of or behind the black hole.

    And, you're right. Compared to the expansion of the universe, these redshifts/blueshifts are often pretty small. Whenever these measurements are being made, they use filters appropriate to the redshift that the object is at (i.e. a "5000 Angstrom filter" designed for high redshifts may actually let light through at a higher wavelength).
  • I can't say to any major observational breakthroughs that I know of (although they very well may be out there) but new theory seems to suggest that AGN's (Active Galactic Nuclei, of which Quasars are a subset) are a stage of formation of _all_ galaxies, including our own. Observationally, the only data that I know of is the fact that Quasars fluctuate on a scale of a few days or weeks, which can only be understood if they are small and the only way things that small can give off that much energy from material falling into a black hole. . .
  • Astronomers generally don't worry about piddly little details like factors of 2 or 3. Often the potential error associated with making the measurement itself can make the point moot, especially when dealing with extragalactic distances, since most of our distance scale calibrations tend to be done "in galaxy". Error propagation isn't fun. Factors of 10, on the other hand, are more serious... In this specific case, however, I suspect someone either made a typo or used a nice, round phrase like "one billion".

    wAnder
  • It's not the velocity of the jet that exceeds c. It's the velocity of the spot illuminated by the jet. Things like that are called superluminal sources because they _appear_ to go faster than light. Imagine you shining a flashlight on a wall. If you turn the flashlight fast enough, the spot on the wall will move faster than the speed of light even though the flashlight isn't. There are superluminal sources in the earth's atmosphere during thunderstorms (caused by an em pulse from lightning propagating upward from the cloud).
  • Pink holes [bbc.co.uk]
  • You answered your own question. Any redshifted light would be counteracted by the blueshifted light. This is one reason why we see spread in the emission lines from Quasars. (part of the emission line is blue shifted and the other part is redshifted, so the line spreads out) The pink light is from something else. . . probably material in the acretion disk of the black hole.

  • Clarifications (Score:4)

    by Anonymous Coward on Monday May 10, 1999 @01:47PM (#1899014)
    Just anticipating a flood of misconceptions from people who didn't read or only skimmed the article..
    • This doesn't apply to all black holes, just some of them.
    • The pink color isn't coming from the black holes themselves, nor is it Hawking radiation. It's coming from outside the holes (perhaps from accreting material that is orbiting them).

  • Note to self (Score:4)

    by alkali ( 28338 ) on Monday May 10, 1999 @02:03PM (#1899015)
    When seeking information on the Internet about important new developments in astrophysics, using the search term "pink holes" will probably not give you completely satisfactory results with most search engines, even though the hit count may be large.

  • More Info That Might Clear Up Questions (Score:5)

    by Anonymous Coward on Monday May 10, 1999 @02:43PM (#1899016)
    These objects are distant quasars. The quasar population was largest when the universe was around a third of its present size (a redshift of 2) and about a fifth (specifically, one 3*sqrt(3)th) of its current age. At this distance, which is around ten billion light years, the resolution of ground-based telescopes is around five thousand light years (this is a limit set by the Earth's atmosphere). So we know that the whole galactic nucleus of the host galaxy, as viewed by us, is "pink". A quasar should dominate the light output from this region- and the light is emitted from a region a few light-days across. This is known because quasars vary in brightness on timescales of weeks.

    When astronomers refer to colors, typically "red" or in this case "pink" refers to emission of larger amounts of light at long wavelengths at short ones. Given the telescopes used, I would guess that they were observing in the "optical" band, which is from around 350 nm (near UV) to around 800 nm (infrared). These would be emitted by the quasar as UV and would lengthen into this band in the observer frame. At redshift 2, these would be emitted at 117 to 267 nm. So, a better headline would be "black holes found to emit more near-UV than far-UV". Of course, this wouldn't be very striking.

    The accepted mechanism for quasar action is that matter falls toward a black hole, collides with other matter, and emits radiation. In fact, there is an equilibrium where the matter falling in produces enough radiation that radiation pressure keeps more matter from falling in. This process should be very hot and so should produce light that is "blue" even in the far UV region.

    There are, however, some additional details of the procedure. Some quasars have what are called "jets" of ejected material. We know these are extremely fast because the apparent velocity across the line of sight exceeds the speed of light in many cases. This is allowed by relativity if the jet moves at a speed near the speed of light pointing directly at us. The jet phenomenon is believed to be connected with a preferred axis of rotation for the material falling into the black hole, and with "synchrotron radiation" emitted by charged particles accelerated by the black hole's gravity. The report seems to suggest that the "pink" light is connected with the jet phenomenon, perhaps in cases where the jet is pointed directly at us.

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