# MeerKAT radio telescope measures neutral hydrogen power spectrum directly, at 6.2 sigma significance

- Published: 2026-11-15 18:41 UTC
- Section: Sky & Space › Astronomy
- Tags: MeerKAT, MeerKLASS, neutral hydrogen, 21-cm intensity mapping, power spectrum, redshift 0.42, cosmic web, radio astronomy, Square Kilometre Array
- URL: https://realtech.media/news/rt-e9ae180237a96bd5bd1467d4_meerkat_radio_telescope/

**The MeerKLASS collaboration measured the 21-cm hydrogen power spectrum at redshift about 0.42 without galaxy catalogues, using MeerKAT data from 2021.**

![MeerKAT radio telescope measures neutral hydrogen power spectrum directly, at 6.2 sigma significance](https://realtech.media/media/2026/11/5bb14599d49d0207.jpg)
*Serge Yerin (YeS), Wikimedia Commons, CC BY 4.0*

The international MeerKLASS collaboration has made the first direct measurement of the neutral hydrogen power spectrum on cosmological scales, without reference to catalogues of known galaxies, ixbt.com reports. The measurement was made with the South African MeerKAT radio telescope. Its significance is 6.2 sigma [1].

## Intensity mapping of the 21-cm line

Neutral hydrogen emits radio waves at a wavelength of 21 cm, and their frequency shifts because the Universe expands. Instead of resolving individual galaxies, astronomers measure the total hydrogen emission over large patches of sky. The resulting maps make it possible to reconstruct the gas distribution and trace its clumps and sparse regions, which are tied to the cosmic web, the network of galaxies and the filaments of matter connecting them [1].

The team used observations from 2021. The telescope covered about 236 square degrees of sky, and the signal came from a region of the Universe at redshift of about 0.42, which corresponds to an epoch roughly 4.5 billion years ago. The emission was recorded in the 971 to 1024 MHz band. The main difficulty was separating the faint hydrogen signal from much brighter radio sources and interference, including emission from the Milky Way and effects of the instrument itself [1].

To tell the cosmological signal from measurement errors, the researchers split the observations into four independent subsets. Each was processed separately to remove foreign components, and the resulting maps and spectra were then compared. This approach suppressed uncorrelated instrumental noise and allowed the team to check whether the common structure of the signal persisted across independent datasets [1].

## What was measured and its limits

The key difference from earlier results is that the team measured the hydrogen emission's own power spectrum, not only its correlation with the positions of already known galaxies. The power spectrum is a statistical measure of how strongly the hydrogen distribution varies across spatial scales. The authors obtained an estimate of the clustering amplitude, which depends on the cosmic density of hydrogen and its linear bias relative to the distribution of matter [1].

The measurement so far covers a limited range of scales. Data processing still requires control of residual interference and of losses of the cosmological signal. The authors note that some spectra of individual subsets contain excess power from systematic effects that were not fully removed, so for the final result they chose a more conservative combination of independent measurements. The detection nevertheless shows that the method can isolate the hydrogen signal without an external galaxy catalogue [1].

MeerKAT is a precursor of the future Square Kilometre Array (SKA) observatory [1].

## Sources

1. [ixbt.com](https://www.ixbt.com/news/2026/11/15/radioteleskop-meerkat-vpervye-napriamuiu-izmeril-raspredelenie-kosmiceskogo-vodoroda-na-bolsix-masstabax.html)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-e9ae180237a96bd5bd1467d4_meerkat_radio_telescope/