Unraveling the Mystery: How a Dead NASA Satellite Fooled Astronomers for Over a Year
Unraveling the Mystery: How a Dead NASA Satellite Fooled Astronomers for Over a Year
For over a year, astronomers were puzzled by a powerful, mysterious blast of radio waves detected in June 2024 by the Australian Square Kilometer Array Pathfinder (ASKAP). Initially believed to be a Fast Radio Burst (FRB) originating from billions of light-years away, the signal has now been definitively traced back to an unexpected source: Relay 2, a long-defunct NASA satellite launched way back in 1964.
This revelation has turned a cosmic enigma into a fascinating terrestrial puzzle. While most FRBs are thought to come from distant galaxies and are often associated with highly magnetized neutron stars called magnetars, this ‘pseudo-FRB’ was remarkably close, only about 2,800 miles (4,500 kilometers) from Earth. Its extreme brightness was simply due to its proximity, not its astronomical power.
The discovery, made by chance during a search for genuine FRBs, highlighted the unique characteristics of this signal. It lasted less than 30 nanoseconds, significantly shorter than typical FRBs which range from microseconds to milliseconds. Despite its brevity, it was strong enough to overshadow other cosmic signals.
The biggest lingering question for the research team is how a satellite that ceased operation in 1965 could spontaneously emit such a powerful, nanosecond-long radio pulse. Scientists are exploring two primary theories: electrostatic discharge (ESD) or a micrometeorite impact. ESD, a sudden spark from a build-up of electricity, is a strong contender, especially given that older spacecraft like Relay 2 were not designed with the same charge-reduction materials as modern satellites. However, typical ESD events last much longer than 30 nanoseconds.
The micrometeorite theory suggests a tiny fleck of space dust could have struck the satellite, creating a cloud of charged plasma and a radio flash. Yet, predictions for such events also indicate longer signal durations than observed. Researchers slightly favor the ESD scenario, noting similar, though longer-lasting, signals observed from GPS satellites by the now-collapsed Arecibo telescope.
Crucially, astronomers assure that this ‘pseudo-FRB’ does not undermine the validity of other FRB detections. Modern telescopes are adept at pinpointing the host galaxies of true FRBs, and a key giveaway for the Relay 2 signal was its minimal dispersion measure—a time delay at lower frequencies that indicates how far a signal has traveled through space. The lack of significant delay in the Relay 2 signal confirmed its nearby origin.
This unexpected discovery, while not a cosmic breakthrough, offers valuable insights. It underscores the need for radio telescopes like ASKAP to be vigilant for human-made signals that could be mistaken for astrophysical phenomena. More importantly, it opens a new avenue for using these powerful instruments to monitor satellites for damaging events like ESD, which are notoriously difficult to track from the ground. The team hopes to detect more such bursts in the future to better understand and potentially mitigate satellite damage.
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