The Search for Extraterrestrial Intelligence (SETI) has been ongoing for more than sixty years, with the official start of Project Ozma at the Greenbank Observatory in West Bank, Virginia in 1960. Led by renowned astronomer Frank Drake, this survey aimed to monitor two nearby Sun-like stars, Epsilon Eridani and Tau Ceti, for signs of potential extraterrestrial technological activity.
Since then, numerous surveys have been conducted using different wavelengths to search for technosignatures around other stars. While no conclusive evidence has been found to prove the existence of advanced civilizations, there have been instances where scientists could not rule out the possibility.
In a recent paper published in the journal Acta Astronautica, veteran NASA scientist Richard H. Stanton described the results of his multi-year survey of more than 1300 Sun-like stars for optical SETI signals. Stanton observed two identical pulses from a Sun-like star located approximately 100 light-years from Earth, matching similar pulses observed four years ago from a different star.
Stanton, a former NASA Jet Propulsion Laboratory (JPL) engineer, has dedicated his retirement to the search for extraterrestrial intelligence using the telescope at the Shay Meadow Observatory in Big Bear, California. Unlike traditional SETI surveys that utilize radio antennas, Stanton’s survey focuses on optical signals, specifically pulses of light that could result from laser communications or directed-energy arrays.
The field of optical SETI traces its roots back to a 1961 study by Schwartz and Townes, who proposed that intense nanosecond laser pulses could be used by extraterrestrial intelligences to send optical signals that outshine their stars. Stanton’s approach involves observing a single star for approximately one hour using photon counting to sample the star’s light at a high time-resolution, searching for pulses and optical tones.
After years of searching, Stanton reported an unexpected “signal” while observing HD 89389, an F-type star in the constellation Ursa Major. The signal consisted of two fast, identical pulses 4.4 seconds apart, not detected in previous searches. Detailed comparisons ruled out various natural phenomena as potential sources of the signal, making it a unique and unexplained observation.
Further analysis of historical data revealed another pair of pulses around HD 217014 (51 Pegasi), a main-sequence G-type star located about 50.6 light-years from Earth. This star, known for hosting one of the first exoplanets ever detected, exhibited similar pulse patterns, challenging conventional explanations for the observed signals.
Stanton’s work highlights the ongoing efforts in the search for extraterrestrial intelligence and the potential for unexpected discoveries in the vast cosmos. As scientists continue to explore new technologies and methodologies in SETI research, the possibility of finding evidence of advanced civilizations beyond Earth remains an intriguing and elusive goal. There are several intriguing possibilities when it comes to explaining the mysterious pulses of light detected from a distant star. One possibility is that the pulses are caused by starlight diffraction by a distant body in the Solar System. Another possibility is that partial eclipses are being caused by Earth satellites or distant asteroids. There is also the concept of ‘edge diffraction’ by a straight edge, as described by the Sommerfeld Effect.
One fascinating possibility is that a gravity wave could be responsible for generating these pulses. Additionally, there is the intriguing notion that the pulses could be the result of extraterrestrial intelligence (ETI). As astronomer Stanton pointed out, whatever is modulating the light from these stars must be relatively close to Earth, suggesting that any ETI activity would have to be within our own Solar System. However, Stanton emphasizes that more data is needed to draw any definitive conclusions.
He stated, “None of these explanations are really satisfying at this point. We don’t know what kind of object could produce these pulses or how far away it is. We don’t know if the two-pulse signal is produced by something passing between us and the star or if it is generated by something that modulates the star’s light without moving across the field. Until we learn more, we can’t even say whether or not extraterrestrials are involved.”
There are existing examples of Optical SETI (OSETI) or LaserSETI initiatives, such as the collaboration between Breakthrough Listen and the Very Energetic Radiation Imaging Telescope Array System (VERITAS) Collaboration. Stanton’s method offers potential for future SETI surveys to search for similar optical pulses. He suggests using synchronized arrays of optical telescopes to track the movement of any objects between the star and Earth, as well as observing events with telescopes separated by a few hundred kilometers to study the arrival time differences of each pulse.
In conclusion, the discovery of these unexplained pulses from a distant star opens up a realm of possibilities and challenges for astronomers. By employing innovative methods and technologies, researchers may be able to shed light on the origins of these mysterious signals and potentially uncover new insights into the nature of our universe.
