Astronomers Detected a Mysterious Radio Burst. It Turned Out to Be From a Dead NASA Satellite
The signal detected last year came from Relay 2, a communications satellite that has been defunct since 1967
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Last year, Australian scientists picked up a mysterious burst of radio waves that briefly appeared brighter than all other signals in the sky. Now, the researchers have discovered the blast didn’t come from a celestial object, but a defunct satellite orbiting Earth.
When the team at the Australian Square Kilometer Array Pathfinder (ASKAP), a system of 36 radio telescopes in Western Australia, detected the 30-nanosecond pulse last June, they thought they were looking at a fast radio burst (FRB). These powerful flashes of radio waves often come from highly dense objects like neutron stars, and they usually originate in distant galaxies. But further analysis revealed that the signal came from our own Milky Way.
“We got all excited, thinking maybe we’d discovered a new pulsar or some other object,” says Clancy James, a researcher at Australia’s Curtin University who is on the ASKAP team, to Alex Wilkins at New Scientist.
After taking a closer look, however, the team realized that the only viable source for the burst was NASA’s dead Relay 2, a short-lived satellite that hasn’t been in operation since 1967. Their findings were published in a pre-print paper on the arXiv server that has not yet been peer-reviewed.
The researchers also discovered that at the time of the event, the satellite was only around 2,800 miles away from Earth, which explains why the signal appeared so strong.
Fun facts: NASA's Relay 2 satellite
- Relay 2 was launched in 1964, two years after its partner Relay 1, as an experimental communications satellite.
- The two satellites were the first used to convey the results of an American presidential election to Europe in 1964, stating that Lyndon B. Johnson had won the vote.
The reason behind Relay 2’s sudden burst is not clear, but the team has come up with two potential explanations—and neither involves the satellite coming back to life like a zombie. One relates to electrostatic discharge—a build-up of electricity that can result in a sudden blast. Spacecraft get charged with electricity when they pass through plasma, and once enough charge accumulates, it can create a spark. “New spacecraft are built with materials to reduce the build-up of charge, but when Relay 2 was launched, this wasn’t well-understood,” explains James to Space.com’s Robert Lea. The other idea is that a micrometeorite hit the satellite, releasing a small cloud of plasma and radio waves.
Karen Aplin, a space scientist at the University of Bristol in England who was not involved in the study, tells New Scientist that it would be tough to differentiate between signals produced by each of those two scenarios, because they would look very similar.
The researchers say they favor the first idea, however, because micrometeorites the size of the one that could have caused the signal are uncommon. What’s more, the former Arecibo Observatory detected electrostatic discharge from GPS satellites, although those bursts were longer-lasting. Still, “we don’t know,” says James to Space.com.
Aplin tells New Scientist that the research points to the usefulness of future efforts to monitor electrostatic discharges from satellites. “In a world where there is a lot of space debris and there are more small, low-cost satellites with limited protection from electrostatic discharges, this radio detection may ultimately offer a new technique to evaluate electrostatic discharges in space,” adds Aplin.
The researchers echo that sentiment to Space.com, adding that these discharges are difficult to monitor. Adam Deller, an astrophysicist at the Swinburne University of Technology in Australia and a study co-author, tells the outlet that he hopes scientists can detect more of these signals in the future and come up with a model for how electrostatic discharges occur. “It would be great if that turned out to be useful in terms of helping to avoid damage to satellites,” he adds.
