Astronomers have been watching nearby stars for decades, trying to understand how they behave and how their planets might influence them. Most of that work has relied on visible light, infrared surveys, and X ray data. A new project has now added radio bursts to that list in a very serious way. The results come from a massive set of observations from the Low Frequency Array, a network of antennas across Europe that listens to the sky at the lowest radio frequencies that can reach the ground. These frequencies reveal magnetic activity, rapid bursts, and energetic events that do not show up in ordinary starlight. Until now, these signals have been extremely hard to detect and even harder to study.
The team behind this project reprocessed more than a year of Low Frequency Array data and created a new method that can pick out short radio bursts from many directions at once. This method allowed them to watch almost two hundred thousand points in the sky for changes in circularly polarized radio waves. Circular polarization is important because it often appears when strong magnetic fields accelerate particles. This is true around active stars and also inside the magnetic environments of planets. With this new approach, the astronomers could see events that earlier surveys missed completely.
Out of the large number of targets examined, twenty seven produced clear radio bursts that stood out sharply from the background. Many of these stars had been found in earlier data, but eight had never shown up in any radio observations before. Some of the bursts were strong. Others were faint but still obvious once the new technique isolated the rapid changes in the data. Most lasted between thirty minutes and ninety minutes. One lasted only two minutes and showed a sudden drift in frequency. These events demonstrated that nearby stars can produce short and intense bursts that do not appear in long exposure images.
The bursts were found to be highly circularly polarized. This detail matters because it points to a specific physical process that produces radio waves when electrons move through a magnetic field. The electrons spiral around magnetic field lines and release radio waves at a frequency that depends directly on the strength of the magnetic field. This process is known from planets in our Solar System, especially Jupiter, which produces strong radio bursts when electrons are accelerated near its magnetic poles. It is also found in active stars. The important point is that it produces a distinct pattern that separates it from other kinds of radio noise.
When the researchers looked at the bursts from the nearby stars, several showed shapes in time and frequency that were instantly recognizable. The bursts formed curved structures known from studies of Jupiter. These shapes appear when a narrow beam of radio emission sweeps across the observer as the magnetic field rotates. The signal rises and falls in a predictable way as different parts of the magnetic structure move into view. Some bursts showed two vertical features connected by a flatter top. Others showed a rising or falling leg. These shapes matched the patterns that appear when electrons travel along a magnetic flux tube, such as the one connecting Io to Jupiter.
One detection stood out for how closely it resembled a known example from the Solar System. The star GJ 687 produced a burst that lasted about forty five minutes and reached up to roughly one hundred sixty megahertz. The researchers compared this burst to a classic arc produced by the interaction between Io and Jupiter. The resemblance was clear. Both show a narrow, tall structure at the same time that the signal reaches its highest intensity. Both also show a clear cut-off at the highest frequencies reached during the event. This similarity suggests that the burst from GJ 687 came from a magnetic environment with a strong and organized field structure.
GJ 687 is already known to host a Neptune sized planet. The planet orbits close to the star and moves through a region with high magnetic activity. The researchers calculated the power that a star planet interaction could produce in this system. They used known values for the star’s magnetic field, the expected speed of the stellar wind, and the size of the planet. The predicted power matched the observed burst within the expected range. Even if the planet had only a weak magnetic field of its own, the interaction between the star and the planet’s surrounding plasma would still be strong enough to create the burst. This agreement does not prove the planet produced the event, but it does show that the numbers fit without stretching the physics.
The brightness temperature of the burst from GJ 687 was extremely high. It reached levels that cannot be explained by heat alone, which means the burst came from a coherent process. The power output was comparable to values seen in magnetic interactions inside the Solar System but scaled to the size and energy of a star. The duration also fit the expected crossing time for a narrow beam of radio emission as the magnetic field rotates. When all these details were combined, the researchers concluded that a star planet interaction is a reasonable explanation, although an active region on the star could also create such a burst.
Not every burst in the survey pointed to a planet. Some stars, such as EQ Peg A, are known to experience strong magnetic activity and flares. In these cases the bursts can be explained by processes happening directly on the star. These stars rotate quickly and have powerful magnetic fields. Their bursts can be intense and frequent. The study took this into account and evaluated each burst according to the conditions around the star where it occurred. Some bursts matched expectations for stellar flares. Others showed structures that were more consistent with a rotating magnetic tube, which may indicate a planetary influence.
What makes this project notable is the scale of the data and the method used to uncover these events. The Low Frequency Array produces huge volumes of data. Traditional processing methods average these data into long exposures that reveal faint galaxies and distant radio sources. The new approach does the opposite. It focuses on changes that occur on scales of seconds or minutes. This type of behaviour vanishes in averaged images, which is why so few of these bursts had been seen before. By pulling out the variable part of the signal, the researchers were able to find faint bursts that would normally be buried under normal radio sky noise.
The findings also show that magnetic activity in nearby stars is more common than expected. Many low mass stars are active. Some rotate slowly, while others spin quickly and produce strong magnetic regions. These differences influence how often bursts occur. The survey detected only a small number of bursts out of a huge sample, but this does not mean the events are rare. Many stars may produce bursts at times when the telescope was pointed elsewhere. Others may burst only during certain phases of rotation or when conditions in their magnetic fields reach a specific threshold. The new method makes it possible to monitor more stars more often, which increases the chance of catching these events.
The comparison with Jupiter is useful because it gives a baseline for understanding what the bursts mean. The radio arcs produced by Io moving through Jupiter’s magnetic field have been studied for decades. Their shapes and timing have allowed scientists to learn how energy moves through Jupiter’s magnetosphere. When similar shapes appear in distant stars, it signals that the same physical processes may be occurring there. A planet moving through a strong magnetic field can trigger bursts of radio emission. The discovery of similar arcs around stars suggests that some exoplanets may create their own radio signatures.
This study also highlights that low frequency radio astronomy can reveal information that no other method can provide. The frequencies used come from electrons moving through magnetic fields. They do not depend on starlight or planetary transits. They give direct clues about the size and strength of magnetic structures. For exoplanets this is especially important because a magnetic field can protect a planet’s atmosphere from charged particles. It can also shape the way energy flows between a star and its surrounding space.
What the researchers have shown is that the tools to detect this behaviour already exist. The challenge was finding the right method to extract the weak bursts from the massive datasets. With the new technique in place, the study shows that stars near Earth do in fact produce short and intense bursts of polarized radio waves. These bursts reveal magnetic structures that have remained hidden until now. Some come from active stars. Some may come from interactions with orbiting planets. Many more remain unstudied in existing data.
The work marks a new step in studying the invisible magnetic environments around nearby stars. By watching how low frequency radio waves change over time, scientists can now search for patterns that reveal the motions of electrons, the shapes of magnetic fields, and the possible influence of planets that cannot be seen directly. The signals are faint, but with the right approach they can be detected and studied in detail. The results show that the space around nearby stars is far more active than once assumed and that the magnetic behaviour of those systems can now be explored in ways that were not possible before.
Source Study:
Nature Astronomy (2026), “The detection of circularly polarized radio bursts from stellar and exoplanetary systems.”
