Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

ESA Planck Mission photograph.

  1. Jul 20, 2011 #1
    I want to know as much as I can about this picture.

    Its the most beautiful picture I've ever seen. What an accomplishment. Must have been one heck of a party when they seen this for the first time.

    Now here's what my brain sees when I look at it. The top and bottom are remnants of a "sphere" that was ripped in half when an enormous amount of energy burst through the center.

    Now I would like to know what trained minds see when they look at it.

    What do the different colors represent?

    What is the bright line through the center?

    Why does everything appear to be attached to the bright line?

    I believe the top and bottom are the CMB, if that assumption is correct, why is it shaped and formed the way it is? If that is not correct then what is correct?

    Any information you have on what the picture shows or how it was taken would be greatly appreciated.

    What cooling technology did they use to acquire this picture?
  2. jcsd
  3. Jul 20, 2011 #2
    After reading up a little more I realize the line through the center is our galactic plane which seems obvious now.

    I cant wait to see the final images when the entire CMB is shown. Not that i'll understand what it shows but others will and I can read their papers:)

    What do the tiny variaions in the CMB represent, heat differences?
  4. Jul 20, 2011 #3


    User Avatar
    Science Advisor

    It is indeed a beautiful image. This is a map of microwave radiation. The Planck satellite sits out at the (L2) Lagrange point (a special point in space beyond the Earth where the satellite will orbit the sun at the same angular speed as the earth -- this keeps the earth always in between the satellite and the sun). It maps the microwave sky in every direction. From the satellite's point of view, this map is really a sphere, with each point on the sphere registering a different microwave intensity. For ease of visual inspection, this map is cut open and spread out (a Mercator projection of the microwave sky). The bright central band is the Milky way -- the "equator" of the galactic sphere. The mottled orange and red colors trace the fluctuations in the primordial cosmic microwave background (CMB). The galaxy is brighter because it is warmer; although beautiful, the galaxy is actually a nuisance to cosmologists trying to study the CMB. The galaxy and other foreground emissions can be subtracted, giving an image of only the CMB. Here is an image of the full CMB sky after subtraction obtained by the WMAP satellite -- Planck's older brother:http://apod.nasa.gov/apod/ap050925.html" [Broken]
    Last edited by a moderator: May 5, 2017
  5. Jul 20, 2011 #4


    User Avatar
    Science Advisor

    Sorry, just replied at the same time as you. Yes, those are tiny temperature differences. They truly are tiny: they exist at 1 part in 100,000! These trace the origin of the all large scale structure in the universe -- they are a snapshot of the tiny density fluctuations as they existed when the universe was only a couple hundred thousand years old. They would go on over the next several hundred million years to collapse and grow into galaxies and galaxy cluster and clusters of clusters...

    These initial fluctuations provide a wealth of information on early universe physics, in particular, inflation. Different inflation models predict different patterns for these fluctuations, and so cosmologists rely heavily on intricate CMB analysis to learn about the earliest moments of the universe's history.
  6. Jul 21, 2011 #5


    User Avatar
    Science Advisor

    The different colors are different frequencies of the Planck satellite. The redder colors are from lower-frequency channels, while the bluer colors are from higher-frequency channels. Don't ask me which colors, specifically, are which. I'm not sure.

    Already mentioned, but yes, it's our galaxy, and the sort of wispy stuff you see coming off from that is the dust in our galaxy.

    Yes, that's CMB. The color of the CMB has to do with the specific way in which they chose to weight the different channels to produce the image. But the brighter spots are going to be slightly higher in temperature, the dimmer spots slightly lower.

    Heh, the Planck satellite has some serious cooling systems. They're described very roughly here:

    And in detail here:
  7. Jul 22, 2011 #6
    Thanks for the replies guys, or girls, does anyone know how much more accurately the new mission will map the CMB compared to the old images.
    Can or do we use spectroscopy on the CMB to obtain information on the elements or particles and the quantity of them that sent the light all those years ago.
    If so what other information could we obtain from this technique, what other techniques are used to understand the CMB?
    And finally, and less importantly to me, when the satelite scans the sky, due to expansion, would the images kind of spiral?
    I dont know how to explain it but what I mean is when it is scanning, every split second it is seeing the CMB as further away than it was a moment ago. So as it spins and scans the sky the image should appear to spiral away.
    I mean wouldnt the scientists on this mission have to account for expansion to gain an image of the CMB that was uniform all the way around in terms of distance?
    Thanks for your patience and information.
  8. Jul 22, 2011 #7
    Two more questions I just thought of.
    Correct me if my assumption is wrong but as the CMB moves further away it cools.? If that is so then if we were to somehow cool the telescope to absolute zero, could we see further into the CMB and see it with more detail?
    And two, how does the Planck telescope differentiate between the microwave background and all the other microwaves given off by matter in the Universe?
  9. Jul 22, 2011 #8


    User Avatar
    Science Advisor

    See the second slide of this presentation to see a comparison between Planck and WMAP:
    http://www.google.com/url?sa=t&source=web&cd=2&ved=0CB0QFjAB&url=http%3A%2F%2Fplanck.ipac.caltech.edu%2Fepo%2Fcurricula%2Fgeneral_talk-files%2FPlanck_general-talk-for-web_01.pdf&ei=H3opTqWhHc29tgeToMDXAg&usg=AFQjCNEgI0XNmISuEubou41GDC5un4jcdA&sig2=EKB7FAWj9tsm0aE-diXmaQ" [Broken]. The left is WMAP's measurement of the temperature anisotropies in the CMB; the right is a simulated projection for Planck.

    These are the original photons left over from the big bang. Soon after the big bang, the photons and baryons (including electrons) were tightly coupled together in a plasma, with photons undergoing frequent Thompson scattering with the charged particles. As the energy of the universe dropped, the temperature soon became right for neutral hydrogen atoms to form. After this, the photons effectively decoupled from the neutral hydrogen, and free streamed across the universe -- the CMB was born. So, the CMB photons are the best example that we humans have of a black body spectrum in the universe!

    In principle, yes, the CMB is every second arriving on earth from a slightly further distance. However, this distance is negligibly small percentage of the distance to the CMB in the first place! Neglecting this expansion has effects well beyond the precision of our experiments.
    Last edited by a moderator: May 5, 2017
  10. Jul 22, 2011 #9


    User Avatar
    Science Advisor

    Some of your questions are addressed in this thread:https://www.physicsforums.com/showthread.php?p=3414848#post3414848"
    that has been going simultaneously with this one.
    Last edited by a moderator: Apr 26, 2017
  11. Jul 22, 2011 #10


    User Avatar
    Science Advisor

    Well, the Planck satellite observes the CMB down to about 5 arcminutes in resolution (one twelfth of a degree), while the WMAP satellite only got the CMB down to about 13 arcminutes (a little more than a fifth of a degree). So there's a massive improvement in resolution. This resolution is mostly a function of the optics of the telescope, not the cooling. The cooling allows two things:
    1. Lower noise in the radiometers for the low frequency instrument. This allows Planck to get similar signal-to-noise at low frequencies as WMAP with only one telescope instead of two as with WMAP.
    2. Allows the use of bolometers. Radiometers, as used by WMAP, are basically radio antennas. But these antennas have a very hard time measuring higher frequency signals (above around 100GHz they're basically worthless). So bolometers are used at higher frequencies. The bolometers operate in a different fashion, and do better with higher-frequency radiation, but they need to be supercooled to function.

    Planck also observes the sky in 9 different frequency channels, from 30GHz to 857GHz (by contrast, WMAP observes the sky at 5 channels from 23GHz to 94GHz). By observing the sky at more frequencies, some of which have never been observed on the full sky, Planck allows for much better separation between foregrounds and the CMB. The reason, fundamentally, why many channels are required is that there's a lot of junk between us and the CMB, and different sorts of junk emit different amounts of radiation at different temperatures. Having a lot of channels allows us to distinguish the different stuff we see from one another.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook