Zahlen, bitte! Mysterious nothing with a diameter of 1.8 billion light years
A mysterious, massive cold spot in the cosmological microwave radiation has researchers puzzled: it is larger and colder than anything else in space.
The huge cold spot in the cosmic microwave background radiation data has astounded scientists: it is considered to be much larger and colder than expected in the standard models, and there is nothing comparable. Some researchers even consider the huge cosmic void with a diameter of 1.8 billion light years to be the largest coherent structure that mankind has ever discovered.
The cosmic microwave background (CMB) is a legacy of the still young universe. It was created around 380,000 years after the Big Bang, when the recombination of atoms began, galaxies and galaxy clusters were formed and cosmic radiation was released into the universe.
It can be measured throughout the universe as we know it. The afterglow of this process is invisible to the human eye, but can be measured with special telescopes in the microwave range.
NASA probe measures anomaly for the first time
This oldest light was systematically investigated in the early 2000s by the NASA space probe WMAP (Wilkinson Microwave Anisotropy Probe). The measured regions were littered with warm and cold patches of background radiation, but one region stood out unusually: the area is about 70 microkelvins colder than the average of 2.3 kelvins. It is located in the area of the Eridanus constellation, south of the celestial equator.
(Image: ESA/ Durham University)
Since it could not be completely ruled out whether measurement errors were responsible for the anomaly, little attention was paid to the remarkable cold spot. This changed when the much more powerful ESA space probe Planck began its work in 2009. The WMAP measurement was confirmed: The spot was therefore real.
The researcher Istvan Szapudi from the University of Hawaii in Manoa said in 2015 about the cold spot: "This is possibly the largest single structure that mankind has ever discovered. The explanations for this range from a statistical error to previously undiscovered physics."
Part of the cold spot may be related to the fact that there is also a void within it. Whereby "void" is relative in this case: there is around 30% less matter than in the regions that are full of galaxy clusters. These empty spaces are also called supervoids (void – for "emptiness" or "gap"). The Eridiani supervoid in the cold spot is around 2 billion light years away from Earth.
Large void could explain part of the cooling
The Eridiani supervoid could explain part of the temperature anomaly. This is due to the so-called Sachs-Wolfe effect, which was discovered in 1967 by the American astronomers Rainer Sachs and Arthur Wolfe: Gravity exerts an influence on the energy of light particles.
In the early universe, matter was closer together, and so was the effect of the gravitational force acting on the individual particles of light (photons): it received energy. However, if it reached a region that exerted less gravitational force, it lost energy and became colder.
(Image: NASA)
Prof. Carlos Frenk, a cosmologist at Durham University, described in 2015 how impressed he was by the discovery: "I'm not so unhappy about the gap itself. It's like the Everest of voids - there must be one that's bigger than the others. But it doesn't explain the whole cold spot, which we're still in the dark about." The Eridanus supervoid can probably only explain about 10 to 20 % of the cooling of the area.
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The anomaly thus contradicted some explanatory models that predicted a similarity of the universe, regardless of which region was being explored. In an investigation in 2022, researchers concluded that the anomaly may have been caused by an event in the earlier universe, or that the standard model is incomplete. Some theories suggest that it could be the result of an interaction under the influence of a parallel universe.
Whatever the case, the cause remains a mystery and is still part of cosmological research. For so long, the giant cold spot will remain a mystery that inspires speculation.
(mawi)
