An international team of astronomers reports detecting an unusual radio signal at about 45 MHz from the red dwarf system GJ 725A, roughly 11.5 light-years from Earth. Using the LOFAR radio telescope, the researchers identified what they describe as coherent radio emission—preliminarily claimed to be the lowest-frequency signal of this kind reliably confirmed from a stellar system. The work involved specialists from the Netherlands Institute for Radio Astronomy and the University of Amsterdam; the findings appear in a preprint on arXiv.org and have not yet completed peer review.
Key Takeaways: The signal is linked to GJ 725A itself, not its companion, and appears in the 42–50 MHz band with a central frequency near 45 MHz. Circular polarization is measured at about 74%; the signal persisted during a one-hour observation but was not seen in other sessions. Its unexpectedly high brightness has pushed the team to consider three explanations, all still unproven.
GJ 725A is a cool, low-mass red dwarf, much smaller and dimmer than the Sun. The system is already known to host a small rocky planet, GJ 725Ab, which completes an orbit in about 11 days. The star itself rotates roughly once every 103 days and is considered very low-activity, making ordinary stellar emission an awkward fit. The broader interest lies in low-frequency radio astronomy: such observations can test how magnetic fields connect stars, planets and moons, but they are also vulnerable to confusion and one-off detections.
The first hypothesis is auroral emission from an undiscovered massive planet in a wide orbit. Even a strong planetary magnetic field may not be enough: if the planet sits far from the star, the stellar wind may lack the power to drive the observed radio emission. The authors therefore speculate that such a planet could have a volcanically active moon, with Jupiter’s Io as a local analogue.
The second hypothesis points to internal activity in the star, though GJ 725A’s slow rotation and low activity weaken that case. The third involves a magnetic interaction between the star and the known planet GJ 725Ab. That explanation also faces a problem: the planet’s mass is estimated at 2.8 ± 0.4 Earth masses, and standard models suggest this is too little to sustain the required magnetic field. The roughly 74% circular polarization and high brightness remain the strongest reasons to doubt routine emission mechanisms.
For now, the result should be treated as provisional. The team will need repeat LOFAR observations, independent telescope confirmation and a clearer picture of the signal’s frequency range, persistence and polarization. If confirmed, GJ 725A could become a useful case study for star–planet magnetic interaction; if not, it may join the list of intriguing but unexplained radio detections. The researchers themselves stress that a single observing run is not enough for a definitive claim.
Source: kun.uz