Fast Radio Bursts (FRBs) have remained a mystery to astronomers even since the first was detected in 2007 (known as the Lorimer Burst).
These quick bursts typically last for mere nanoseconds, though some have been found to last up to 3 seconds, and their precise cause remains unknown.
In recent years, scientists have traced a few FRBs back to their source and have determined that they came from neutron stars.
This has led to the theory that FRBs are caused by compact objects, though this has yet to be proven.
On June 13th, 2024, scientists at the Australian Square Kilometer Array Pathfinder detected a potential Fast Radio Burst (FRB) that lasted just 30 nanoseconds.
The pulse had a bandwidth of 695.5 MHz – 1031.5 MHz, which was strong enough to temporarily eclipse all other radio signals in the sky, leading scientists to speculate that it must have come from a distant cosmic source.
In a recent study, a team of astronomers and astrophysicists determined that the FRB did not come from a distant astronomical source, but from NASA’s Pathfinder 2 mission, a now-defunct satellite orbiting Earth.
The study was led by Clancy James, an Associate Professor with the International Centre for Radio Astronomy Research (ICRAR). He and his ICRAR colleagues were joined by researchers from the Center for Astrophysics and Supercomputing at Swinburne University of Technology, the Royal Observatory at the University of Edinburgh, the Inter-University Institute for Data Intensive Astronomy at the University of Cape Town, the Australia Telescope National Facility, the Sydney Institute for Astronomy, the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav), and the Royal Melbourne Institute of Technology.
The Relay 2, launched in 1964, was the second in a series of early American satellites designed to test communications technologies. While Relay 1 provided the first American television transmissions across the Pacific Ocean, Relay 2 conducted radio transmissions for a year before it ceased operations.
Its final broadcast was of Senator B. Everett Jordon (D-N.C.) opening the International Exposition of the American Textile Machinery Association in 1965. However, the mission continued to operate until 1967 when its two transponders failed and further communications ceased.
When the FRB was detected in June 2024, it was assumed that the signal had come from a distant cosmic source since this was the case with most previously-detected events. However, subsequent analysis showed that it came from a source closer to Earth, eventually leading the team to Relay 2.
As they describe in their study, the team traced the burst using Skyfield Python Module 1, an astronomy program used to compute the positions of stars, planets, and satellites in orbit, which showed the Relay 2 satellite within the observed FRB’s timeframe and position:
Skyfield also calculates the distance between ASKAP and Relay 2 at 4322 km at the observation time — reasonably consistent with the estimated distance of 4500 km ± 80 km. An angular distance of 3.2′ corresponds to 4 km in the plane of the sky at a distance of 4322 km… [T]he position on the sky, as seen from ASKAP, of the observed burst location and Relay 2 in a five-second window centred on the observed burst time. We therefore conclude that this burst originated with Relay 2.
They also determined that the signal was so strong because it was passing directly over the SKAP when it occurred, which explains the clarity of the signal itself.
As for what caused the burst, the team dismissed the possibility that Relay 2 temporarily came back online. Instead, they attribute it to electrostatic discharge (ESD), which has been observed with satellites in the past. This occurs when electrostatic charges build up on a satellite or spacecraft until it reaches the point where it will discharge in a large burst.
Another possibility is that it was due to a charged plasma cloud caused by a micrometeorite collision.
These results could lead to new tools for studying FRBs and other signals, and could also lead to new techniques for monitoring the movement of defunct satellites. They also suggest that radio observatories searching for cosmic rays – like the Low Frequency Array (LOFAR) and the Auger Engineering Radio Array (AERA) – will be able to identify nanosecond-scale FRBs.
This, they argue, could help future surveys to distinguish between cosmic events and interference from local objects:
In particular, experiments measuring radio emission from high-energy particle cascades search for impulsive signals of 1–100 ns duration (Schröder 2017), and regularly encounter RFI on these timescales.
This makes bursts (be they due to ESD or micrometeoroid impacts) a potential impostor signal for experiments looking for radio-emission from high-energy particles. Conversely, such astroparticle experiments could readily be made capable of detecting space-borne impulsive radio-frequency events.
Written by Matthew Williams/Universe Today.
