When Will We Know If Planck Discovered B Mode Polarisation?

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Discussion Overview

The discussion revolves around the anticipated release of the first all-sky Cosmic Microwave Background (CMB) map by the Planck mission and its implications for detecting B-mode polarization. Participants express excitement and skepticism regarding the potential findings, the timeline for data release, and the challenges associated with measuring polarization.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation

Main Points Raised

  • Some participants express excitement about the upcoming results and the possibility of new discoveries, while others caution that the findings may only refine existing data from WMAP.
  • Concerns are raised about the delay in data release, with speculation that it may be related to addressing systematic effects, such as the "axis of evil" phenomenon.
  • Participants note that the polarization signal is significantly weaker than temperature anisotropies, making it more challenging to obtain reliable results.
  • There is a suggestion that Planck was not primarily designed for polarization measurements, which could limit its effectiveness compared to dedicated polarization experiments like EBEX.
  • Some participants believe that while the discovery of B-mode polarization is unlikely, there remains a small chance that Planck could achieve this, although confirmation may take an additional year.
  • Discussion includes the complexity of systematic effects in polarization measurements, highlighting how they can impact results differently than temperature measurements.

Areas of Agreement / Disagreement

Participants generally agree that the detection of B-mode polarization by Planck is uncertain and that the release of relevant data may be delayed. However, there is no consensus on the likelihood of Planck successfully discovering B-mode polarization or the implications of the findings.

Contextual Notes

Participants mention the challenges of systematic effects in polarization measurements, which may complicate the interpretation of results. The discussion reflects a range of assumptions about the capabilities of the Planck mission and the nature of the data being released.

Who May Find This Useful

Readers interested in cosmology, particularly those following developments in CMB research and polarization measurements, may find this discussion relevant.

skydivephil
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In case you didn't know already the first all sky Cmb map will be released at a press conference at ESA HQ March 21st
http://smsc.cnes.fr/PLANCK/Fr/GP_actualites.htm
This will be followed by a conference to discuss the cosmological data in Holland April 2nd-April 5th.
http://congrexprojects.com/13a11
 
Space news on Phys.org
Ohhh, nice. Can't wait to see the results!
 
And only a couple months late ... were they trying to smooth out any 'axis of evil' effects? [a conspiracy theory thing].
 
Im excited by this prospect, we could get something really new. But on the other hand it could just be WMAp to a few extra decimal places, that would be so dissapointing.
Hopefully if so there be a bit more interest to build a deidcated b polarisation mission.
 
Chronos said:
And only a couple months late ... were they trying to smooth out any 'axis of evil' effects? [a conspiracy theory thing].
Haha, well, I think it's been set for March for quite some time, though I don't recall precisely.

Anyway, I think the main thing that makes it take so long is nailing down the systematic effects, such as the precise beam shapes and noise properties. These can all have subtle and difficult-to-nail-down impacts on the scientific products.
 
skydivephil said:
Im excited by this prospect, we could get something really new. But on the other hand it could just be WMAp to a few extra decimal places, that would be so dissapointing.
Hopefully if so there be a bit more interest to build a deidcated b polarisation mission.

I was in a seminar listening to Martin Bucher from Planck Mission today, he said that we have to wait *another year* for polarization data... :rolleyes:
 
yenchin said:
I was in a seminar listening to Martin Bucher from Planck Mission today, he said that we have to wait *another year* for polarization data... :rolleyes:
That sounds about right to me. The polarization signal is much, much lower, which means it's much, much harder to nail the systematic effects down well enough to make for a good signal. It doesn't help that Planck wasn't really built to be a polarimeter: it was built for temperature anisotropies. Polarization was tacked-on later, and it's actually not all that good at it. It should still be better than WMAP for polarization, of course, but dedicated polarization experiments, such as EBEX, are much, much better when it comes to controlling systematic effects related to polarization.
 
I have been under the impression that whilst discovering the B mode polarisation is unlikely, there is some small chance that Planck could do this.
However from what I read above, it appears that even if it does make this discovery ( i know its not desinged for that) we won't know about it this MArch/ April, but it's another year away?
 
skydivephil said:
I have been under the impression that whilst discovering the B mode polarisation is unlikely, there is some small chance that Planck could do this.
However from what I read above, it appears that even if it does make this discovery ( i know its not desinged for that) we won't know about it this MArch/ April, but it's another year away?

That's my understanding from the seminar; we will know soon later this month if they do release any polarization data.
 
  • #10
skydivephil said:
I have been under the impression that whilst discovering the B mode polarisation is unlikely, there is some small chance that Planck could do this.
However from what I read above, it appears that even if it does make this discovery ( i know its not desinged for that) we won't know about it this MArch/ April, but it's another year away?
Right. Polarization data is really really finicky, and subject to all sorts of potential problems. One major issue is that systematic effects which cancel when performing a temperature measurement may add and become even larger when taking a polarization measurement.

This is becomes the temperature signal comes from averaging the value of the polarization signals together, while the polarization signal comes from subtracting them. So if one systematic effect pushes one signal up while the other signal goes down, the temperature signal is unaffected, but the polarization signal sees a huge result. And because the actual polarization signal is only a small fraction of the temperature signal, any systematic effects that remain in the data are bad news.
 

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