The Roar Of Space

Space is typically thought of as a very quiet place. But one team of astronomers has found a strange cosmic noise that booms six times louder than expected.

The roar is from the distant cosmos. Nobody knows what causes it. And it is going to kill us all (not really, but I don't know).

Of course, sound waves can't travel in a vacuum (which is what most of space is), or at least they can't very efficiently. But radio waves can. Radio waves are not sound waves, but they are still electromagnetic waves, situated on the low-frequency end of the light spectrum. Many objects in the universe, including stars and quasars, emit radio waves. Even our home galaxy, the Milky Way, emits a static hiss (first detected in 1931 by physicist Karl Jansky). Other galaxies also send out a background radio hiss.

But the newly detected signal is far louder than astronomers expected. Using the balloon-borne instrument named ARCADE (Absolute Radiometer for Cosmology, Astrophysics, and Diffuse Emission), it was launched from NASA's Columbia Scientific Balloon Facility (I had no idea we had one) in 2006, and reached an altitude of about 120,000 feet where the atmosphere thins into the vacuum of space.

ARCADE's mission was to search the sky for faint signs of heat from the first generation of stars, but instead they heard a roar from the distant reaches of the universe. Detailed analysis of the signal ruled out primordial stars or any known radio sources, including gas in the outermost halo of our own galaxy. Other radio galaxies also can't account for the noise – there just aren't enough of them. The signal is measured to be six times brighter than the combined emission of all known radio sources in the universe.

For now, the origin of the signal remains a mystery.