Measuring distances in the universe is no easy task. Almost all methods rely on light, which can be absorbed by dust, scattered, or distorted along the way. It's like trying to spot a distant lighthouse through fog and haze. Neutrinos are a different story. These ghostly particles pass through anything without noticing obstacles.
A team of astronomers decided to build a new "distance ladder"—a method that uses neutrinos instead of the usual light-based rungs. They took data from the IceCube neutrino observatory spanning 14 years and selected 12 galaxies (Seyfert galaxies with active nuclei) that showed a notable excess of neutrinos. The key idea: link a galaxy's neutrino luminosity to its X-ray luminosity. This is similar to judging the power of a speaker by the loudness of its sound, even if the speaker itself is out of sight.
In the end, the Hubble constant (which indicates how fast the universe is expanding) came out to about 49 km/s per megaparsec. The uncertainty is still large — roughly 40 km/s on the plus side and 30 on the minus. But the important thing is this: it's the first time such a measurement has been made using neutrinos. And it is free from the distortions that are inevitable for light.
So cosmologists have a new tool, like adding a quiet but crystal-clear channel to a noisy radio receiver. The signal is still weak, but over time, as data from new neutrino telescopes accumulate, this "ladder" could become much more precise.
as written by the authors arXiv:2608.00923v1
Measuring distances in the Universe is one of the hardest problems in physics and astronomy. Almost every distance probe relies on photons, whose propagation across cosmic distances introduces extinction, absorption, scattering, and radiative-transfer effects. Neutrinos suffer none of these and propagate unattenuated through dust, intergalactic medium, and dense source environments alike. We introduce a new distance-ladder method for measuring the Hubble constant $$H_0$$ using high-energy astrophysical neutrinos from point sources as standardizable candles, and report its first observational realization. Using 12 X-ray-selected Seyfert galaxies for which IceCube reports significant per-source neutrino excesses in its 14-year public point-source release, we exploit the disk-corona correlation $$L_ u = \kappa\, L_X^\beta$$ between neutrino and X-ray luminosities to construct a neutrino distance ladder anchored by non-redshift distances to NGC 1068 (Cepheid + TRGB). We find $$H_0 = 49^{+40}_{-30}\,\mathrm{km\,s^{-1}\,Mpc^{-1}}$$ and $$\beta = 0.67^{+0.16}_{-0.25}$$ (68% credible intervals), with the corona slope disfavoring the calorimetric limit $$\beta = 1$$ at $${\sim}2\sigma$$. The result is consistent with existing $$H_0$$ determinations from Planck and SH0ES within 1$$\sigma$$. While the uncertainty on $$H_0$$ is large, the measurement is free of electromagnetic propagation systematics and demonstrates the viability of neutrinos as a novel cosmographical probe.
Neutrinos interact so weakly with matter that they can pass through a light-year of lead without noticing. Every second, about 100 billion neutrinos from the Sun pass through your body.
In Stanisław Lem's novel "His Master's Voice," neutrinos are used to receive a signal from space: there they play the role of an ideal information carrier, unaltered by the medium.