The Big Ear Radio Telescope in Delaware, Ohio, was disassembled in 1998 having operated for over 30 years. It was replaced by a golf course. Big Ear was never the world’s biggest radio telescope, nor its most sensitive. But Big Ear nevertheless made one of the most famous observations in the history of astronomy, one that till this day has never been explained.
Throughout the 1970s, Big Ear searched for signals from extraterrestrial civilizations. And on Aug. 15, 1977, it found one — a strong, intermittent signal lasting for 72 seconds, that stood out from the background noise like a searchlight.
The team quickly ruled out a terrestrial origin or a broadcast from a satellite. Nevertheless, the signal was so powerful and unusual that Jerry Ehman, the astronomer who analyzed the data print out, annotated the signal with the word “Wow!”.
The director of the observatory, John Kraus, later gave a detailed account of the observation: “The WoW” signal is highly suggestive of extraterrestrial intelligent origin, but little more can be said until it returns for further study,” he wrote, in a letter to the astronomer Carl Sagan.
The Big Ear team continued to observe the same part of the sky, as have others, but the Wow! signal never returned. Nor has anything like it been observed in any other part of the sky.
Kraus and others have even searched for stars that could be the source of the signal: “We checked star catalogs for any Sun-like stars in the area and found none,” wrote Kraus. To this day, the Wow! signal remains unexplained and unrepeated.
Which is why the discovery this week of a probable source is significant news. The finding is the result of some clever sleuthing by an amateur astronomer and the creation of a fabulous new 3D map of the galaxy.
First, some background. Back in 2013, the European Space Agency launched the Gaia space observatory to map the night sky — to determine the position, the distance, and the motion of stars with unprecedented accuracy. So far, Gaia has mapped some 1.3 billion stars, allowing astronomers to begin creating the most detailed 3D map ever made of our galaxy. The mission is expected to continue until 2024.
Gaia’s new star map has significantly improved our understanding of the galaxy and the stars within it and this gave amateur astronomer Alberto Caballero an idea. The Gaia database is now significantly more detailed than the star catalog that John Kraus studied in the 1970s. Perhaps the new database might reveal the source of the Wow! Signal, he reasoned.