A team of astronomers has detected a message from the dead. According to a new paper published on arXiv, a burst of transient radio waves that was detected in June 2024 was actually a signal from an inactive NASA satellite.
Though the occurrence of the signal is surprising, it isn’t that the dead satellite spontaneously restarted, turning on and resuming its transmissions to astronomers and observatories on Earth. Instead, the team says that this signal was probably due to an electrostatic discharge, or ESD, event — an accumulation of electricity that disperses with a radio-signaling spark.
“Our observation opens new possibilities for the remote sensing of ESD,” the team wrote in its paper, “and reveals a new source of false events for observations of astrophysical transients.”
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Short Radio Signals
Radio signals come from all corners of space, and they tell astronomers much about the structure and composition of the celestial objects around us. Indeed, not only do radio telescopes capture radio waves from planets, stars, and galaxies; they also catch signals from comets and clouds of charged gases, as well as from pulsars and many of the other occupants of far-off space.
While searching for a type of faraway radio transmission called a fast radio burst (FRB) — which are thought to be released by magnetic neutron stars, or magnetars — astronomers operating the Australian Square Kilometre Array Pathfinder (ASKAP), a terrestrial radio telescope located in Western Australia, detected a surprisingly short signal. The burst was less than 30 nanoseconds long — a remarkably short duration for any radio burst.
Using the location of their observations and the time of the burst, the team discovered that the radio waves were not from a star, a galaxy, or any other distant astronomical source, but a deactivated communications satellite called Relay 2, which continues to orbit Earth, around 2,800 miles away.
The spacecraft was sent into orbit in 1964, and its operations were officially stopped in 1965. The next year, the first transponder that the satellite carried to transmit and receive radio signals lost its functionality, and a year after that, the second failed, too, leaving the spacecraft inactive for almost 60 years.
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A Surface Spark?
The team behind the discovery says that the signal was not a result of Relay 2’s transponders.
“While re-commencement of transmissions by defunct satellites has been observed, a [30-nanosecond] pulse does not naturally correspond to any on-board system,” they wrote in the study. “We therefore rule out that the burst was a deliberate transmission.”
Rather than a revival of the dead, it is probable that an electrical charge accumulated on the surface of the satellite as it traveled through space, sparking an ESD shock and sending out a sudden radio wave signal.
ESD radio signals have been detected from the surface of other satellites orbiting Earth in the past, with several similar observations made by a radio telescope in Puerto Rico. But these signals have tended to be longer than the burst from Relay 2.
“ESDs have previously been observed with the Arecibo radio telescope,” the astronomers wrote in the study, “but on 1,000 times longer timescales.”
Another possibility is that a collision with a micrometeorite produced an observable spark and radio signal, though these flashes, too, are typically longer than the burst observed by the team.
While both explanations are feasible, the astronomers say that they find the ESD theory more convincing, in part because of the age of the satellite, which was made with older materials that were more susceptible to ESDs.
“We suggest that the burst originated from an electrostatic discharge (ESD) event, or potentially a micrometeoroid impact, and consider that such events may be relatively common,” the astronomers concluded in their paper. “The observation of such a short burst […] is unexpected, and raises the prospect of new methods of remote sensing of […] discharges from satellites.”
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
arXiv. A Nanosecond-Duration Radio Pulse Originating From the Defunct Relay 2 Satellite
NASA. Radio Waves
NASA. Relay 2
Sam Walters is a journalist covering archaeology, paleontology, ecology, and evolution for Discover, along with an assortment of other topics. Before joining the Discover team as an assistant editor in 2022, Sam studied journalism at Northwestern University in Evanston, Illinois.
