The "Wow!" signal is one of the greatest space mysteries.
On August 15, 1977, a strong narrow band radio signal was detected by the Ohio State University's Big Ear Radio Telescope during a search for extra-terrestrial intelligence (SETI). The signal, which lasted for 72 seconds, was so remarkable that astronomer Jerry Ehman, who discovered it days later, wrote "Wow!" on the printout, giving it its famous name. The signal originated from the direction of the constellation Sagittarius and has been considered one of the best candidates for an alien radio transmission.
The Search for the Source
Despite numerous attempts to find a source of the "Wow!" signal, it has never been determined with surety. This has led to various theories about its origin. Some scientists suggest it might have been a natural cosmic event or interference from a terrestrial source. However, the possibility that it was a message from an extra-terrestrial civilization remains a tantalising hypothesis. Recent research has pointed to a Sun-like star about 1,800 light-years away as a possible source, although this has not been confirmed.
As per the BBC, the signal was concentrated on the region of the radio spectrum at wavelength 21.106 cm and frequency 1420.406 Mhz. This is called the hydrogen line, emitted by accelerated hydrogen atoms, the most common element in the Universe.
Competing Theories
One of the prominent theories proposed by Antonio Paris in 2016 suggests that the "Wow!" signal could have been caused by the passage of a hydrogen cloud accompanying one of two comets (266P/Christensen and P/2008 Y2) that were in the same part of the sky at the time. This idea would explain why the signal was not measured again - the comet that caused it moved on in its orbit. However, this theory remains controversial, with some astronomers arguing that it does not fully explain the characteristics of the signal.
In 2017, Paris and his team again surveyed the sky around Sagittarius using a telescope when Comet 266P/Christensen was passing through this region. They determined that the signal of 266P/Christensen (and three other comets) matched the "Wow!" signal.
Cultural Impact and '3 Body Problem'
The "Wow!" signal has not only fascinated scientists but has also permeated popular culture. Netflix series '3 Body Problem', based on the science fiction trilogy by Liu Cixin, integrates the "Wow!" signal into its storyline. In the series, the signal is portrayed as a real message from an alien civilization, leading to dramatic consequences for humanity. This creative use highlights the enduring intrigue and mystery surrounding the "Wow!" signal.
The Ongoing Mystery
The "Wow!" signal remains one of the great unsolved mysteries in the search for extra-terrestrial intelligence. While some researchers continue to investigate potential natural explanations, the possibility that it was an intentional signal from another civilization keeps the curiosity alive. Until a repeat signal is found or a definitive explanation is provided, the "Wow!" signal will continue to be a source of wonder and speculation in both the scientific community and beyond.