Spiral galaxies seen edge-on often show dark lanes of interstellar dust blocking light from the galaxy's stars, as in this image of the galaxy NGC 4565 from the Sloan Digital Sky Survey (SDSS-II).
Spiral galaxies seen edge-on often show dark lanes of interstellar dust blocking light from the galaxy's stars, as in this image of the galaxy NGC 4565 from the Sloan Digital Sky Survey (SDSS-II).

Astronomy

Intergalactic Dust Could Be Messing Up Observations, Calculations

26 Feb , 2009 by

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“Just like household dust, cosmic dust can be a nuisance,” said astronomer Ryan Scranton of the University of California, Davis. Scranton is part of a team of researchers from the Sloan Digital Sky Survey that have been analyzing the colors of distant quasars whose light passes in the vicinity of foreground galaxies on its way to the Earth. What they found is that the vast expanses of intergalactic space appear to be filled with a haze of tiny, smoke-like “dust” particles that dim the light from distant objects and subtly change their colors. “Galaxies contain lots of dust, most of it formed in the outer regions of dying stars,” said team leader Brice Ménard of the Canadian Institute for Theoretical Astrophysics. “The surprise is that we are seeing dust hundreds of thousands of light-years outside of the galaxies, in intergalactic space.”

An implication of this finding means that since most distant supernovae are seen through some haze, our current estimates of their distances may be affected.

Dust grains block blue light more effectively than red light. “We see this when the sun sets: light rays pass through a thicker layer of the atmosphere,” said Scranton, “absorbing more and more blue light, causing the sun to appear reddened. We find similar reddening of quasars from intergalactic dust, and this reddening extends up to ten times beyond the apparent edges of the galaxies themselves.”

The team analyzed the colors of about 100,000 distant quasars located behind 20 million galaxies, using images from SDSS-II. “Putting together and analyzing this huge dataset required cutting-edge ideas from computer science and statistics,” said team member Gordon Richards of Drexel University. “Averaging over so many objects allowed us to measure an effect that is much too small to see in any individual quasar.”

Supernova explosions and “winds” from massive stars drive gas out of some galaxies, Ménard explained, and this gas may carry dust with it. Alternatively, the dust may be pushed directly by starlight.

“Our findings now provide a reference point for theoretical studies,” said Ménard.

Intergalactic dust could also affect planned cosmological experiments that use supernovae to investigate the nature of “dark energy,” a mysterious cosmic component responsible for the acceleration of the expansion of the universe.

Intergalactic dust doesn’t remove the need for dark energy to explain current supernova data, Ménard explained, but it may complicate the interpretation of future high-precision distance measurements. “These experiments are very ambitious in their goals,” said Ménard, “and subtle effects matter.”

The new findings are reported in a paper titled “Measuring the galaxy-mass and galaxy-dust correlations through magnification and reddening,” submitted to the journal Monthly Notices of the Royal Astronomical Society, and posted today on the web site arXiv.org.

Source: Sloan Digital Sky Survey

By  -        
Nancy Atkinson is currently Universe Today's Contributing Editor. Previously she served as UT's Senior Editor and lead writer, and has worked with Astronomy Cast and 365 Days of Astronomy. Nancy is also a NASA/JPL Solar System Ambassador.


24 Responses

  1. Fst says:

    I’m not an astronomer and I know I’m going far here, so please someone clarify it to me: could this mean that redshift is caused by intergalactic dust and that maybe the universe is not expanding at all?

  2. Jack says:

    It certainly screwed up your spellchecker, re calculCations…!!!

    Damn that intergalactic dust!!!

  3. Ethan Siegel says:

    No way, Fst. The dust is going to have subtle effects only, it doesn’t change any of the conclusions people have drawn about cosmology, redshift, or dark energy.

    I’m just posting here to avoid alarmism; this is an extremely minor correction to measurements.

  4. Astrofiend says:

    “# Fst Says:
    February 26th, 2009 at 3:02 pm

    I’m not an astronomer and I know I’m going far here, so please someone clarify it to me: could this mean that redshift is caused by intergalactic dust and that maybe the universe is not expanding at all?”

    >>>No – this is a separate effect. Redshift and ‘reddening’ are two different things. Note that there is a theory flying about that states that redshift could be caused by interstellar gas and dust, but almost no astronomer or physicist believes it – it has major problems apparently.

    Anyway – back to the original question. This reddening that the article speaks about is essentially why we see sunsets as red – in the sunset case, the atmosphere preferentially scatters bluer light, leaving redder light to pass through less hindered. The redder the light is, the more likely it is to pass through the atmosphere unhindered, and vice versa. It is due to an effect called Rayleigh Scattering. Essentially interstellar/galactic dust has the same effect – it allows light of a longer wavelength to pass unscattered more than light of a shorter wavelength. The net effect is that the light we see from any object beyond the dust will appear dimmer and redder due to the bluer light being scattered out of our line of sight by the dust.

    This affects distance measurements for supernovae etc because such measurements rely on the ‘absolute luminosity’, or intrinsic brightness of the event to gauge its distance. Hence, an unaccounted for dimming effect will have a bearing on the result of such calculations, though probably small. It is important to note that in this effect, the spectral lines that make up the light do not get ‘shifted’ to the red – they stay right where they should be, given the distance to the object. Rather, objects appear redder and dimmer due to the action of removal of blue light from the stream of photons that we eventually see.

    The separate phenomenon of ‘redshift’ (the term here being used in its most common meaning – i.e. in relation to the expanding universe) is where actual spectral lines of atoms – the ‘light fingerprint’ that they emit is shifted to the red end of the spectrum by the direct action of the expansion of the universe i.e. the wavelength of the light of a given frequency when emitted is subsequently stretched by the expansion of space-time itself. The net effect of this is not really a reddening of such objects in visible light, because as blue light gets shifted down to red, so UV light gets shifted down into the blue and so on. Rather, The spectral lines move to the red end of the spectrum, and hence do not appear where they should be. This is a direct indication of the action of the expansion of the universe.

  5. Lotusface says:

    These are the subtleties that will clue us in to the real nature of the universe, we have been almost correct in our observations of the place. When we find the difference between the environment inside & outside of the heliosphere there will be additional minor corrections and likewise with the milky way locale. I know in my bones that the “supernatural” ideas some have will be explained by subtle discoveries like this(way down the timeline).

  6. robbi says:

    Fst- I’m not an astronomer either, but the ‘general’ distance to close to distant galaxy are correct enough for ‘general amateur astronomers-too many indicators out there says our Universe is expanding, one is if the Universe is ‘static’ or not expanding is, ALL the light from distant galaxies should’ve brighten up our Universe far more than what we see, and our ‘night’ sky would not be so dark! What this feed is about is, ‘fine tuning’ of our Universes’ expansion and recently found/theorized data from distant Supernova Type 1A that our Universe is accelerating the expansion, the acceleration is real and forever took the heat off Cosmologist and general Astronomers why the previous rate of expansion and age according to the ‘Big Bang’ theory , will place the age of the Universe is less than the oldest stars!! It appears the interstellar dust between galaxies is more dense than previously thought, and will require further ‘fine tuning’ . I’m certain far more knowledgeable persons will explain other indicators why our Universe is expanding and accelerating the expansion

  7. OilIsMastery says:

    Well I guess that would explain the myopia and scotoma of mainstream science.

  8. Dave says:

    #Fst: Im no astronomer either, but i think the evidence for the expanding universe is seen in the spectral lines in the light from different galaxies ( absorption lines from various elements like hydrogen etc)…the lines themselves are shifted to the red, and more so the farther away the galaxy in question is…all the dust would do is attenuate the light at various colours, but the spectral lines would not be shifted…the shift is due to the expanding universe having something like a Doppler effect on the lines due to space itself getting bigger while the light in question is on the way to us…..any experts on here care to clarify?

    #oilsmastery: huh? What you mentioned doesnt explain anything…or make sence.

  9. Steven C says:

    Well, as with all things big and small … theories are based on observed phenomena. Many theories that seemed to explain the observed phenomena later proved to be “fantasy”. As observations accumulate, some theories fade because no amount of “fine-tuning” of the theory permits the observed phenomena to be satisfactorily explained. The origin of the Moon is as good an example as there is. When I was in School, the universally accepted theory said that the moon was thrown out of a rapidly spinning young earth – the division theory. Only in the mid to late 1980’s did scientific community embrace and shift to the glancing impact of a planet sized object as the theory of choice — a theory that had lain in ill repute for over 30 years before finally being embraced when it was proven in simulations that you could run the Earth-Moon backwards in time and never arrive at a point where they merged. I am not a professional astronomer but I still find “dark matter” and now “dark energy” to be unsettling as both were invented to “fine tune” preserve our current theories. Based on what has been observed to date, we still cannot detect or prove that “dark matter” or “dark energy” exists. I often wonder if scientists should not look more carefully at what has been observed and not observed and go back to square zero and find a theory that doesn’t need a lot of fine tuning and “dark stuff” to be consistent with what has been observed. Red shifts seem to the Holy Grail of the astronomical community and the “accepted” theory of red shifts and using those theories to infer distances and such has led us to this point.

    What if our theories about red shifts are only partially correct. There was a curious theory that proposed quantum based red shifts but this might upset all of our distance measurements so it has become very unpopular.

    Perhaps we need to re-examine the basis of our theories and, perhaps, “dark matter” and “dark energy” really are unnecessary.

    Perhaps we have gotten it wrong all along and we need some fresh viewpoints.

    I will state bluntly that I don’t know what the answers are Astronomers have been 100% sure in the past only to abruptly switch to another theory …

    I don’t know but all this talk of “fine tuning” seems to be “major tuning”.

    What if the “void” is teeming with dust and debris. Maybe all this “dark matter” is really just “dim” matter.

    I am sure that Astronomers/Astrophysicists a hundred years from now will look back at some or most of our “quaint” prevailing theories and smile with amusement.

  10. robbi says:

    Steven C Says-In the late 50s’ I was a child and wonder why looking at a map, S.America was a perfect fit with Africa-everyone saw that, so I asked the teacher why does S.America,Africa and so many other areas looks as if they all fit to another, I was told the it’s all a coincidence and the mountains are a shrinking effect, I had a heated discussion with the teacher and said why doesn’t the whole Earth look like a prune- well I had to see the principal lol. Coninental drifting was fully published by Alfred Wegener in 1912,but convention scientist and geologist at the time and later called him a nutcase and worst. It wasn’t until the 1960s’ that geologist and scientist, still fighting to the last, accepted Continental Drifting. The most convincing thing I have about the expansion of the Universe is from Olbers’ paradox 1862, although he really was not the first to think of the reason why is the night sky so dark if we have an infinite universe—-at that time, galaxies other than our Milky Way was not known. Still, when Galaxies were recognized and the numbers keeps on expanding,, if the Universe is ‘Static’ or not expanding, the light form the trillions of Galaxies should brignten up our Universe much more than what we have. Lets face it, Science in general evolves as slow as a snail, and current scientist hates changes and don’t like to be considered wrong. Anyone who ‘goes against the grain’ is considered a quack and worst . I try to keep an open mind and think ‘outside the box’, and don’t really accept all conventional facts, but, funding goes to the ones with ‘conventional proven results’ or so it seems, and the ‘old school’ scientist will fight to the bleeding end to prevent funding to anyone who has theories that contradicts current conventional thinking. Since I have retired as a Network Administrator 2 1/2 years ago, I am just a serious amateur astronomer and ‘puter geek
    and really try to stay neutral on these ‘exchange of truth’.If you read about the asteroid feed, you will know what I mean.!!!

  11. robbi says:

    Steven C Says-There are 2 strange things
    that makes my thinking about the Comets and the Solar Wind kinda hazy-=I was near Perth ,Austrailia in Jan-Feb07 on vacation there and thru New Zealand. I saw Comet McNaught-it was brighter than Comet Hale-Bopp, the brilliant tail as seen even with the naked eyes and then a 25x125mm binoculars had the most oddly quick changing tail that show brilliant lanes far frome the nucleus that Solar Wind alone can not cause, because the changes were so quick and startling, I checked if there was auroras increased sighting, none. Than Comet Holmes. it was so far from the Sun and yet became bright enough to see with the naked eye in dark areas, solar wind can not work that far from the Sun.
    Einsteins Theories will continue to dominate 100 years from now-practical applications are when cosmic rays hits other certain sub-atomic particles traveling near speed of light-the life ot that particle should have been in a certain nanoseconds or about 10miles or 16KM , but such particle lives long enough to sometimes hit the Earths’ surface showing the effects of something perfectly when traveling near speed of light, the life of the particle slows drastically compared to relatively stationary objects. His theories have so far passed all tests. However, there are a few things in Astonomy like Comets that says something else is also involved.

  12. robbi says:

    Steven C Says- Interesting when you said about the divsion theory about Earth-Moon system as in the late 50s’ it was the Sun pulling enough mass from out molten Earth that created the Moon-and the void was the Pacific Ocean which of course before Drifting Continent was finally accepted by scientist and Geologist . In the late 60s to about 2000 when wine,woman, family and song messed up my mind, I finally got back to get my own large ‘scope with the ‘puter control etc. and retired at age 55 in late 2006. In the late 70s’ I was asking my young sons what the teacher said how the Moon was created, most students had already said a collision and the teacher said nothing!!! People in the US in general to the mid 60s’ believed in ‘creationism’ while me and others who had an open mind as I am an agnostic believes in catastrophism. Many people in the US into the 70s’ still could not believe the Earth could have such violent changes, while I knew if I was in some countries like Indonesia, volcanos rules!!! In 1980 I was living in the Portland, Ore metro area, and Mt St Helens collapased with a incredible landslide and the blast was directed toward the NW which killed people directly 25 miles away, in the Earth overall sceam of things this was a decade event but El Chichón Volcano in Mexico blew 2 years later blasting more ash about 20miles or 32kilometers up and giving us some nice Sunrise,Sunsets until Mt Pinotubo outdid all in 1991. Back to Mt St. Helens, there was some religious he-be je-be freaks who though Mt St Helens will not run dare blow, I said,’WHY NOT’,they said because we are a Christian Country-I said dont’ give me that BS, Earth will do will it will do, and does not respect anyones religions. They didn’t want to talk to me because they though I was a devil.lol. When the thing blew May18,1980, and I went to work Monday May 19th, I said, why didn’t your religion protect those people killed and destroyed much besides the ashfall hundred of miles away still with a few inches of ash on the ground. Those religious freaks shut up from then on Lol.
    In 100 years, I believe humans will still not go to Mars because I believe without any basis for facts outer space beyond Earths’ atmosphere is quite deadly-we had the Apollo missions to the Moon, but humans were out of the Earths’ only for a few days.
    The findings of UltraHighEnergyCosmicRays
    some time ago told me, if the Earths’ atmosphere stops >99.9% of those beasts, I said damm.!! Articles I’ve read from various sources believes 6M people on Earth die yearly from cancer, the mysterious type where the patient was just seen by the doctor and had routine tests done,then the next day the patient feels kinda sick,gets really sick then a few hours later goes to the doctor, the doctor sees the patient was in bad shape and ordered tests, it should it appeared it may have started in the thyroid section but the spread was something that was not ot the types usually caused by thyroid cancer as this spread is relatively slow. The entire body was affected wihtin minutes from the start, and the patient was hospitalized and the patient lost so much weight and a bag of bones in 3 weeks the patient died. The patient did not have a history of cancer in the family and in no cancerous areas. The doctor then checked thruout the US and other doctors said an incredible ‘strange’ quick all body cancer had affect some patients the same way from time to time, and a small database was started and still being organized. As more research is done, if found it affected all ages, races, cultures and is just like a ‘bolt out of the blue’
    All patients had no history of cancer or in a cancerous area, and they think back to doctors they replaced and they knew of similar cases Some checks were made overseas to Japan, Europe, China and they also said of this ‘lightning quick cancer’ and fast death within a month. The theory, which I think has a lot going for it, says 6M are killed yearly by this mysterious cancer caused by the Universes’ cosmic rays and UHECR. I believe our Suns Heliosphere stops >99% of ‘true’ outer space deadly charged particles. Some time, in the next few centuries, a probe will be sent well out the Suns’ Heliosphere and bow shock or well away from the Sun influence (about 500-1000 a.u.)and measure the type of radiations out there .I believe it will be quite deadly, the only way I think and I have read articles about this is to mimic the safety of being in Earths’ atmosphere in ‘True Outer Space’ is to have 21 meters or 66 feet of lead shielding around the spaceship-gezzzzz,where are they going to get that much lead from and what true guarentee is this!! There will be many discoveries done, but many theories from Einstein will still rule with some additions and modifications done
    In 100 years, the changes will not be as drastic as it was from1909 now that the shackles of creationism and religion does not shackle our discoveries and thinking for the last few decades

  13. Aodhhan says:

    Never amazed by the amount of misinformation given by people who know just enough about astronomy to be dangerous.

    To address the redshift question/problem. In a very simple way.

    Long wavelengths appear red. The longer the wave is, the darker and more rich the red color appears.
    Short wavelengths appear blue. The shorter and more compact, the deeper and more rich the blue color.

    Think of a slinky, and imagine the coils as light waves. As distance increases between the two ends of the slinky, the wave lengths become greater, and the slinky would turn redder. Increase the distance more, and wavelength increases, and the red light becomes richer.

    If you compacted the slinky, the distance between the two ends are closer, and the wave length much shorter; thus appearing more blue.

    Simply, distance stretches light waves.

    Essentially, the slinky always contains both red and blue. However, when it is stretched, the red becomes richer and the blue becomes more sparse, but it is still there.

    Since dust affects the shorter wavelengths the most, you get the affect there is less blue light than there actually is, so you get the appearance that an object is redder, and we falsely interpret the object being further away than it actually is.

    So, does this mean the universe isn’t really expanding?
    No. This problem only appears when there is a lot of dust between us and the object we are viewing. There are plenty of areas where we observe far away objects without dust in the way.

  14. Chris says:

    Aodhhan,

    How can we now be certain that there is no dust between us and some arbitrary far-distant object? If it took us this long to come to the realization that there is some dust in intergalactic space nearby, isn’t it possible that there is even more accumulated dust the further away we look? In other words, how can we possibly discount the possibility that we’re seeing something “clearly” without the effect of dust when we’ve been seeing this (allegedly) small dust effect the entire time?

  15. ND says:

    Aodhhan,

    I think you’re confusing reddening and redshifting. They’re different phenomenon. redshifting is a measure of how far spectral lines have shifted because of the speed of the object along the line of sight, regardless of how much reddening may occur. Reddening is basically like looking through a reddish filter.

  16. jerry says:

    The study throws a major wrench in the supernova cosmological studies. Specifically, relativistic reddening IS difficult to discern from dust reddening.

    In the current supernova distance determinations, there is little reddening budget assigned to dust; and this lack of dust in the supernova sample is statistically inconsistent with the amount of dust implied from this general study.

  17. collin says:

    Distance does not stretch wavelengths, velocity does. It’s the same concept of hearing a fire engine speed away from you and the siren drops in pitch. If the fire enging was stationary, the pitch would be the same whether it was 5 feet away from you or 100 feet away.

    My problem is this…I can’t seem to reconsile the difference between the *appearance* of reddened and redshifted light. How would we know which is which? The perception of red is just the wavelength of light that hits our lenses so what would be the difference of light that came in at red wavelengths due to redshifting or reddening? I guess I might argue that this dust phenomenon, while not washing away expansion theory, might account for some of the rate of expansion that we thought was occuring before.

    I don’t know…you’ve got to keep an open mind…we are like infants sitting in a car trying to figure out how it works.

  18. Aodhhan says:

    ND, No I’m not confused at all. Reddening is throwing off the accuracy of redshift measurement. How about that? :)

    Chris, could be a can of worms. I’m going to hold off for a bit to see what sort of consistencies (or lack of), distortion, etc turn up with further study.

    Another question; is there any “magnified” affect of this reddening when observing far away galaxies via gravitational lensing.

  19. jerry says:

    Dust ‘reddening’ is not consistent at all wavelengths, whereas doppler redshift is; so within margins of error, you can compare the attenuation in different spectral ranges and differentiate between doppler redshift and dust reddening.

    At very high velocities; general relativity causes a ‘reddening’ effect in addition to the doppler shift in the frequency bands.

    Supernova researchers have concluded, or at least assumed, that most of the reddening they observe is due to relativistic effects, not dust.

    It is a degenerative problem, in that if you assume or conclude there is substantial dust reddening, then you also must presuppose that the most distant supernova events are much brighter and/or much closer than current distance estimates. The difference is substantial: You can no longer substantiate that the ‘accelerating cosmic expansion’ ‘proven’ in the late 1990’s is real: A more likely scenario is that we don’t have a good handle on distant supernova absolute magnitude.

  20. Aodhhan says:

    Collin, you have it all wrong. If what you said was the case (since the speed of light is constant) there would be no redshifting. I would have also spent a lot of my career wasting time.

    Please study more about the doppler affect.

  21. ND says:

    collin,

    The following wiki entry is a good overview of redshift and how it’s measured.

    http://en.wikipedia.org/wiki/Redshift

    Redshift can be measured for wavelengths outside of the visible spectrum.

  22. ND says:

    Aodhhan,

    What career are you in?

  23. robbi says:

    In the relatively near future with advanced space scopes and ground based scopes using various filters and specialized detectors, they will eventually find the zone of ‘nothing’, this is NOT the area where the Universe ends, it is part of space that has receded faster than the speed of light-this does not break Einsteins rule as space itself is expanding and not the objects like ‘baby galaxies’. These objects have receded into ‘nothing’ because they are in space > speed of light and forever gone from view, dispite the best detectors available and would be dimmer than the Universes ‘glow’ from the leftover of the Big Bang.
    To get past this glow is to create gravitrons detectors which is thousands of times more difficult than creating a true neutrino ‘scope’ or viewing ALL neutrinos in ‘movement’ which is far,far beyond out current technology
    and knowledge, this is probably something in the 3000 millennium
    In short, they will find the edge of zone of ‘nothing’ or objects in space that travel > speed of light forever gone, even if they ever create a gravitron detector, those objects past the zone of ‘ nothing’ is forever gone from view

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