In space, no one can hear you scream, but with the right equipment, it is possible to detect a roar. The instrument that detected the mysterious roaring signal was the Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission (ARCADE), which NASA built to extend the study of the cosmic microwave background spectrum to lower frequencies.
The scientific objectives of the mission, while ARCADE floated high above Earth's atmosphere, 37 kilometers high, free of interference from our planet, were to find heat from the first generation of stars, search for relics of the particle physics of the Big Bang, and observe the formation of the first stars and galaxies.
ARCADIAN
The first evidence of this space roar Was discovered by Alan Kogut and his NASA team,1 the announcement was made in issue 213 of the American Astronomical Society on January 7, 2009.
ARCADE was able to make 'absolutely calibrated zero level' measurements, meaning it was measuring the actual brightness of something in real physical terms rather than relative terms. This was different from typical radio telescopes, which observe and contrast two points in the sky. By looking at all the 'light' and comparing it to a blackbody source, ARCADE was able to see the combination of many dim sources. That's when the intensity of a particular signal became evident..
ARCADIAN
Since then, scientists have sought to see where the radiation comes from while seeking to describe the properties of the signal. The latter became evident quite quickly. According to Al Kogut, who led the ARCADE team at NASA's Goddard Space Flight Center in Greenbelt, Maryland
It is a diffuse signal that comes from all directions, so it is not caused by a single object. The signal also has a frequency spectrum, or 'color', that is similar to the radio emission from our own Milky Way galaxy.
Scientists call the signal 'synchrotron radio background', the background is an emission from many individual sources and blends into a diffuse glow. But because the 'space roar' is caused by synchrotron radiation, a type of emission of high-energy charged particles in magnetic fields, and because each source has the same characteristic spectrum, it is difficult to identify the origin of this intense signal.
The mysterious thing is that the signal is six times stronger than expected: It has been known since the late 1960s that the combined radio emission from distant galaxies should form a diffuse radio background coming from all directions. The space roar is similar to this expected signal, but there appear to be six times as many galaxies in the distant universe to make up the difference, which could point to something new as the source.
It is now being debated whether this source is inside or outside the Milky Way. Still, one reason it probably isn't coming from our galaxy is because the roar doesn't seem to follow the spatial distribution of the Milky Way's radio emission. Once you know with certainty where it comes from, you have to determine what it is.
The American physicist David Brown, For example, has pointed out that space roar could be 'the first big empirical success of M-theory', a broad mathematical framework that encompasses string theory. 'There could be a Fredkin-Wolfram automaton scattered across a multitude of alternate universes, producing recurring physical time with endless repetitions of all possible physical events.' What this means is that the early universe had much more real matter than today, which explains the powerful radio signal.
Other possible, less theoretical sources could be large-scale diffuse mechanisms, such as turbulently merging galaxy clusters, or an entirely new class of incredibly numerous, previously unknown, individual sources of radio emission in the universe. Anything along those lines is highly speculative at this point, and some suggestions that have been floated include dark matter annihilation, supernovae from the first generations of stars, and many others.
Some scientists have suggested that gases in large galaxy clusters could be the source, although it is unlikely that ARCADE's instruments would have been able to detect radiation from any of them. Similarly, there is a possibility that the signal was detected in the earliest stars or originated in many otherwise faint radio galaxies, the cumulative effect of which is what is being recorded with ARCADE. But if this were the case, then they would have to be packed together incredibly tightly, to the point that there is no gap between them, which seems unlikely.
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The news
The strange 'space roar' detected by NASA's ARCADE instrument
was originally published in
Xataka Science
by
Sergio Parra
.