The Planck Collaboration Opens The Kimono

Hot on the heels of the Moriond Conference (during which CERN officials announced that they are confident that the Higgs-like boson announced last July 4 is, in fact, a Higgs boson), the ESA’s Planck Collaboration have plopped out 30 papers announcing the results thus far of the Planck Satellite’s examination of the Cosmic Microwave Background (CMB), the cosmic “afterglow” of the Big Bang, discovered back in 1964 by Arno Penzias and Robert Wilson.

Cosmic Microwave Background (Image credit: ESA, Planck Collaboration)

Capturing the CMB at even higher resolution than the WMAP mission, Planck’s data have allowed the team to produce a refined plot of the CMB fluctuation angular power spectrum, including values for multipole moment l>1000 (for which WMAP had no solid data), corresponding to smaller angular features. (E.L. Wright has a great tutorial on the CMB power spectrum.)

Power spectrum of temperature fluctuations. (Image credit: ESA and the Planck Collaboration)

While I haven’t really had a chance to dive in, there are a lot of goodies here. In summary:

  • The data refines estimates of the age of the universe to 13.82 billion years. Estimates based upon WMAP data pegged this at 13.73 billion years.
  • The Planck data indicates a Hubble constant (the rate at which the universe is expanding) of 67.3 kilometers per second per megaparsec, slightly lower than the previously estimated value of 74.2 km/s/Mpc. (This constant is a tricky beast to measure accurately, but that is a story for another day.)
  • Estimates of the composition of the universe are a bit different from those obtained from WMAP data as well:
    • 4.9% baryonic (normal) matter – up from 4.6% from WMAP data
    • 26.8% dark matter – up from 24% from WMAP data
    • 68.3% dark energy – down from 71.4% from WMAP data
  • An anisotropy in the CMB observed in WMAP is confirmed. One side of the CMB is a bit warmer on average, and the opposite side is a bit cooler. It is a subtle effect, but it is there. This could have profound implications for the generally accepted assumption in cosmological models of isotropy. Or, it could be a statistical fluke. Unfortunately, we only have a sample size of one universe, so it is difficult to tell based upon the available data. (Here is something that Sean Carroll wrote about this anisotropy in 2008.)
  • In the power spectrum, there seems to be some suppression of fluctuations at large angular scales. (In other words, there are non-Gaussian deviations in the distribution of fluctuations.) This could help refine inflationary models.
  • Neff has a measured value of 3.3 ±0.5, consistent with Standard Model predictions assuming only three neutrino species. This dampens hopes for the discovery of sterile neutrinos (neutrinos which do not interact via the weak nuclear force), despite recent results from the MiniBooNE experiment hinting at the possibility of sterile neutrinos. (This result means that I’ll have to update several sections of the neutrino physics “mega-post” that I’ve been working on for over a year. Will I ever finish that bloody thing?)

As I have already indicated, I haven’t really had time to dive in, but there are plenty of others commenting on this.  Here are some of the best sources:

Background material on the CMB:


About Glen Mark Martin

MCSE-Messaging. Exchange Administrator at the University of Texas at Austin. Unrepentant armchair physicist.
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3 Responses to The Planck Collaboration Opens The Kimono

  1. John says:

    A few other points:

    1. The octupole and quadrupole are aligned with the ecliptic (as in the WMAP), so Planck has pounded the final nail into the Copernican Principle.
    2. The “axis of evil” persists, though Lawrence Krauss, Copi, Huterer, etc. hoped otherwise, so the Cosmological Principle is gone.
    3. The anomalies occur at the largest angular scales, which invlaidate LCDM for this universe, and inflation.
    4. The big bang theory needs to be jettisoned.
    5. We do live in a special place.

    • The “Axis of Evil” anomaly does not necessarily invalidate either the Copernican Principle or the Cosmological Principle, although it certainly forces a re-evaluation. Keep in mind that there exist potential explanations that are consistent with current models, including contributions due to peculiar motion of our galaxy and local cluster, as well as the prospect of this being a statistical fluke that would look different from some other vantage point in the cosmos. But, given that we have observational sample size of one visible universe, that is challenging to test.

      The anomalies at large angular scales by no means invalidate either the Lambda-CDM model or inflation, although these results due severely constrain inflationary models. Hybrid inflation is pretty much ruled out, and chaotic inflation is in jeopardy. “Slow-roll” inflationary models are still on the table.

      As for invalidating the basic Big Bang model, there is nothing here that does that.

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