CMB Acoustic Peaks

Explore real Planck 2018 temperature–temperature (TT) spectrum measurements. Choose a view and a peak, or enter a multipole ℓ; Show plots the data and reports the nearest available bin in that view. Blue dots are measurements, orange is the supplied binned BestFit reference, green marks the selected bin. Error bars and reference can be toggled; CSV exports all original columns for the current view. Click or tap the plot to select a measured bin. Left/Right move between bins; Home/End select the first/last.

Low ℓ means large sky structures, high ℓ means small ones. Angular scale is the rough relation θ ≈ 180°/ℓ, not the precise sound-horizon angle. Acoustic peaks arise from oscillations in the early photon–baryon plasma; small-scale power is damped. Dℓ = ℓ(ℓ+1)Cℓ/(2π) is temperature variance in μK², not the temperature of one point on the sky.

The file contains 83 grouped measurements with effective bin centers from ℓ≈47.7 to 2499.0 and 1σ uncertainties. Peak choices find the largest measured bin in three fixed acoustic ranges; they do not fit a precise peak location. The orange line joins the file’s BestFit bin values. This explorer neither fits cosmological parameters nor creates a sky map or a Boltzmann simulation.

Credit: ESA and the Planck Collaboration, Planck PR3 (2018), TT-binned R3.01. Dataset and definitions; Planck 2018 results V. Data licence: CC BY-NC 3.0 IGO. Data are bundled locally; no external service receives your selections.