A few years ago, astronomers were surprised to detect a very high radio signal with no determined origin, a spatial roar that remains unexplained.
In space, no one can hear you scream, said the poster for the first film in the Alien series. The reason is well known: in the vacuum of space there is no air, and therefore there can be no sound. However, in 2006, NASA discovered something they called “space roar,” a signal six times stronger than anyone expected.
This signal is not a sound, but a radio signal. The space roar was first discovered by ARCADE, the Absolute Radiometer for Cosmology, Astrophysics and Diffuse Emission. It is a detector that NASA attached to a stratospheric balloon, which rose to 36,000 meters in height with the aim of searching for radio signals from distant galaxies.
Radio waves are electromagnetic radiation, just like visible light or infrared light that allows the telescope Webb take amazing pictures. The radio waves that a star like our sun emits are not very different from the light that we receive. That’s why we have huge radio telescopes, like the ill-fated Arecibo. Due to the expansion of the universe, distant light decreases in energy as it travels, and high-energy light ends up being converted into radio waves.
This was ARCADE’s mission, to detect these faint radio signals from distant stars without the hindrance of Earth’s atmosphere. Instead, he was given the radio equivalent of turning on the television at full volume. The researchers described it as a “boom,” six times stronger than anyone had anticipated.
After some investigation, scientists ruled out the idea that they were simply very noisy early stars. They also ruled out that it somehow came from the dust of our own galaxy. It was just a radio burst, dubbed “space roar,” that seemed to be part of the background noise, for no reason.
The roar, or radio synchrotron background emission, is a diffuse signal coming from all directions, so a single object is ruled out. The signal also has a frequency spectrum, or “color,” that is similar to the radio emission from our own Milky Way.
Since the late 1960s it has been known that the combined radio emission from distant galaxies should form a diffuse radio background coming from all directions. What was not expected is its magnitude, which cannot be explained because there do not appear to be six times as many galaxies as are already known. This raises many unknowns regarding its origin.
Although the space roar has piqued the interest of many, there is still no explanation for it. There is still controversy regarding whether it comes from our galaxy, the Milky Way, or from outside it, although the latter is the most likely according to experts. It is also speculated that it is residual radiation extended by many parallel universes, or that it comes from the annihilation of dark matter, or that it is produced by interstellar dust and gas.
In any case, the space roar is a real problem that hinders the capture of radio waves from the first stars following the formation of the universe. One more mystery that science must solve.
