The fit of the number of neutrino species required to match the CMB fluctuation data. Image credit: Brent Follin, Lloyd Knox, Marius Millea, and Zhen PanPhys. Rev. Lett. 115, 091301 — Published 26 August 2015.
(…) Last year, a paper by Brent Follin, Lloyd Knox, Marius Millea and Zhen Pan came out, detecting this phase shift for the first time. From the publicly-available Planck (2013) data, they were able to not only definitively detect it, they were able to use that data to confirm that there are three types of neutrinos — the electron, muon and tau species — in the Universe: no more, no less.
The number of neutrino species as inferred by the CMB fluctuation data. Image credit: Brent Follin, Lloyd Knox, Marius Millea, and Zhen PanPhys. Rev. Lett. 115, 091301 — Published 26 August 2015.
What’s incredible about this is that there is a phase shift seen, and that when the Planck polarization spectra came out and become publicly available, they not only constrained the phase shift even further, but — as announced by Planck scientists in the aftermath of this year’s AAS meeting — they finally allowed us to determine what the temperature is of this Cosmic Neutrino Background today! (Or what it would be, if neutrinos were massless.) The result? 1.96 K, with an uncertainty of less than ±0.02 K. This neutrino background is definitely there; the fluctuation data tells us this must be so. It definitely has the effects we know it must have; this phase shift is a brand new find, detected for the very first time in 2015. Combined with everything else we know, we have enough to state that yes, there are three relic neutrino species left over from the Big Bang, with the kinetic energy that’s exactly in line with what the Big Bang predicts.(…)
Read more at http://www.forbes.com/sites/startswithabang/2016/09/09/cosmic-neutrinos-detected-confirming-the-big-bangs-last-great-prediction/#66a2193b4be4