# Mainz physicists rule out stupendously large primordial black holes as dark matter

- Published: 2026-11-07 04:57 UTC
- Section: Sky & Space › Astronomy
- Tags: primordial black holes, dark matter, cosmic microwave background, Planck observatory, stupendously large black holes, JGU Mainz
- URL: https://realtech.media/news/rt-b160f3d0b0ea72a30be6a9f6_mainz_physicists_rule/

**Analysis of Planck satellite cosmic microwave background data shows stupendously large black holes cannot comprise a significant fraction of dark matter.**

![Mainz physicists rule out stupendously large primordial black holes as dark matter](https://realtech.media/media/2026/11/9bc6db2d7ee7bdee.jpg)
*ESA and the Planck Collaboration, Wikimedia Commons, CC BY 4.0*

Theoretical physicists from Johannes Gutenberg University Mainz (JGU) and the PRISMA+ Cluster of Excellence have ruled out stupendously large primordial black holes as a significant component of dark matter, according to a study reported by EurekAlert and published in Physical Review Letters [1]. The researchers analyzed cosmic microwave background (CMB) measurements obtained by the European Space Agency's Planck space observatory to test whether early universe matter accumulated into ultra-massive black holes.

Primordial black holes are hypothesized to have formed shortly after the Big Bang. Theoretical models suggested that dark matter could have accumulated into stupendously large black holes (SLABs) with masses ranging from 100 million to 10 billion billion solar masses [1]. The researchers evaluated the gravitational impact these objects would have exerted on the matter distribution in the early cosmos.

## Cosmic background perturbations

The cosmic microwave background represents radiation released approximately 380,000 years after the Big Bang. Planck measured fluctuations in this background during its four-and-a-half-year mission before being decommissioned in October 2013. According to the team's calculations, a high abundance of SLABs carrying significant amounts of dark matter would have introduced distinct perturbations into the radiation field, producing a characteristic graininess in the temperature fluctuations [1].

To evaluate the hypothesis, the Mainz physicists modeled the expected perturbations across the microwave sky and compared the simulated signatures directly against Planck's empirical dataset [1]. The observed radiation spectrum lacked the graininess required by the presence of these massive objects, leading the team to conclude that SLABs did not form in sufficient abundance to constitute a substantial fraction of dark matter [1].

## Implications for early cosmos phenomena

The exclusion of large populations of SLABs directly limits potential solutions for other cosmological observations. Stupendously large black holes had previously been considered candidate explanations for the nano-Hertz gravitational-wave background detected by pulsar timing arrays, as well as for the massive early galaxies identified by the James Webb Space Telescope [1]. The authors noted that these phenomena are unlikely to be explained by SLABs given the observational constraints imposed by the CMB analysis.

## Sources

1. [EurekAlert](https://www.eurekalert.org/news-releases/1150845)

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Source: RealTech, realtech.media — https://realtech.media/news/rt-b160f3d0b0ea72a30be6a9f6_mainz_physicists_rule/