In 1977, a radio telescope recorded a 72-second signal coming from the direction of the constellation Sagittarius. Stunned, the astronomer who observed it wrote "Wow!" on the readout. Since it couldn't be explained, plenty argued the signal was proof of life beyond our planet. After 40 years, however, a researcher has finally burst their bubble. Antonio Paris of St. Petersburg College last year suggested the 1420 MHz "Wow!" signal actually came from hydrogen gas surrounding a comet—either 266P/Christensen or P/2008 Y2, which were in the area of the signal at the time but only discovered about 10 years ago, per Popular Mechanics. So when one passed by Earth earlier this year, Paris pointed a radio telescope at it.
Unlike any other celestial source nearby, 266P/Christensen emitted a radio signal at 1420.25 MHz. Paris then pointed his telescope at three other comets selected at random. All appeared to emit a 1420 MHz signal, which hydrogen atoms naturally produce, per the SETI Institute. A SETI researcher told Forbes last month that the signal was likely radio frequency interference. But this shows that '77's 'Wow!' signal "was a natural phenomenon from a solar system body" and certainly not a message from aliens, Paris writes in the Journal of the Washington Academy of Sciences. Or, as the London Times puts it, the Wow signal just "officially lost its wow factor." (A coming telescope will be able to view nearby galaxies in "unprecedented" detail.)