MeerKAT Telescope Discovers 30 New Radio Transient Pulsars Expanding Our Understanding of the Milky Way’s Hidden Neutron Stars
The MeerKAT radio telescope in South Africa has made an impressive new discovery — 30 previously unknown radio transient pulsars, adding significantly to our knowledge of the Milky Way’s population of neutron stars. The detection comes from the MeerTRAP (MeerTRAnsients and Pulsars) project, an international collaboration focused on finding short-lived radio signals in real time.
These discoveries were detailed in a new paper by Jun Tian and colleagues from the University of Manchester, published on October 20, 2025, on arXiv. The results highlight the immense capability of MeerKAT’s wide field of view and high sensitivity for uncovering elusive cosmic phenomena.
What Exactly Are Radio Transient Pulsars?
Radio transient pulsars are rapidly spinning neutron stars that emit irregular bursts of radio waves. Unlike traditional pulsars that emit pulses at highly regular intervals, transient pulsars often send out sporadic, unpredictable flashes — sometimes minutes, hours, or even days apart.
They are part of a larger group known as fast radio transients — brief, powerful radio signals originating from astrophysical sources. When these bursts come from outside our galaxy, they’re known as Fast Radio Bursts (FRBs). However, when they come from within the Milky Way, they are typically linked to highly magnetized neutron stars such as pulsars, magnetars, or Rotating Radio Transients (RRATs).
The 30 new pulsars found by MeerTRAP are thought to be mostly RRATs, given their low pulse rates and sporadic behavior.
How MeerKAT and MeerTRAP Work Together
MeerKAT is one of the world’s most sensitive radio telescope arrays, operated by the South African Radio Astronomy Observatory (SARAO). It consists of 64 dishes spread across the Karoo region, designed for deep-sky radio observations.
The MeerTRAP project runs in parallel with other MeerKAT observations — a commensal search, meaning it collects and analyzes transient data in real time while the telescope performs other science programs. This approach allows astronomers to catch fast, one-off radio events without needing dedicated telescope time.
Using this method, MeerTRAP has already discovered dozens of galactic radio transients, and this latest batch of 30 adds an exciting new layer to that growing catalog.
The Technical Details Behind the Discovery
The team detected the new pulsars through single-pulse searches — instead of looking for continuous, periodic signals, they searched for isolated bursts of radio emission.
These bursts were captured in two of MeerKAT’s observing bands:
- UHF band: 544–1,088 MHz
- L band: 856–1,712 MHz
Of the 30 new transients, astronomers were able to measure the rotation periods of 14 sources, ranging from 0.121 to 7.623 seconds. That means one of these neutron stars spins more than eight times per second, while another takes over seven seconds for a single rotation — slow for a pulsar, but fast for something the size of a city.
One particularly intriguing follow-up observation revealed an even slower pulsar, with a period of about 17.5 seconds — among the longest rotation periods ever detected for a radio pulsar.
The dispersion measures (DMs) — a property that indicates how much interstellar material the radio signal has traveled through — ranged from 12 to 394.4 pc/cm³. This variation suggests that the sources are spread across different regions of the Milky Way, some relatively nearby and others far deeper within our galaxy’s disk.
Emission Features and Unique Behaviors
Three of the newly found pulsars exhibited fascinating emission traits.
- PSR J1243−0435 showed periodic microstructure, meaning its pulses contained fine, repeating substructures within each burst.
- PSR J1911−2020 and PSR J1243−0435 also displayed evidence of nulling, where the pulsar temporarily stops emitting detectable radio waves before resuming again.
Such behaviors help astronomers probe the inner workings of pulsar magnetospheres — the powerful magnetic regions surrounding these dense stars — and can reveal transitions in their emission states.
Measuring Pulse Strength and Patterns
For four of the 30 transients, researchers measured the fluence (total energy received) of their pulses. These values ranged between 0.1 and 2 Jy·ms, with most clustering around 0.3 to 0.7 Jy·ms. Interestingly, the fluence distribution may follow a lognormal pattern, suggesting that the pulses vary in strength but cluster around typical values — a clue to how the emission process works.
The duty cycles — the fraction of time a pulsar is “on” and emitting — were found to be very low. This means these pulsars are “dark” most of the time, lighting up only briefly, which might indicate narrow radio beams or specific geometric alignments with Earth. Such factors make these sources extremely challenging to find and underline why MeerKAT’s sensitivity and data-processing pipeline are crucial.
Locating the Pulsars and Understanding Their Origins
Out of the 30 sources, nine were localized to arcsecond precision, using voltage buffer and coherent beamforming techniques. This accurate positioning is key because it allows scientists to perform follow-up timing and imaging studies, possibly even connecting the pulsars to known supernova remnants or other structures.
The rest of the sources, while detected, still need refined localization to determine their exact positions and distances within the Milky Way.
Why This Discovery Matters
Each new pulsar discovery helps expand the pulsar census — a crucial step toward understanding the population and evolution of neutron stars.
Neutron stars are the incredibly dense remnants of supernova explosions. A single teaspoon of neutron star material would weigh billions of tons on Earth. These objects can spin rapidly and emit powerful radio beams from their magnetic poles, which we detect as pulses when they sweep past Earth — like a cosmic lighthouse.
However, not all pulsars emit regularly. Some, like the ones in this discovery, are intermittent or transient, possibly representing an intermediate stage between active pulsars and silent neutron stars. By studying these elusive objects, astronomers can learn how magnetic fields, spin rates, and plasma processes influence when and how pulsars emit radio waves.
The Bigger Picture and Future Prospects
This discovery highlights just how many hidden neutron stars may still exist undetected in our galaxy. Many of them likely go unnoticed because traditional pulsar surveys rely on periodic signals, missing those that emit only rarely.
MeerTRAP’s single-pulse real-time detection strategy is changing that by catching these brief, random bursts as they happen. The ongoing MeerTRAP survey is expected to find many more RRATs and long-period pulsars in the coming years.
As more data is collected, astronomers will be able to study how often these transients occur, what their population distribution looks like, and whether there’s a connection between these slow, sporadic pulsars and other types of neutron stars such as magnetars.
The MeerKAT telescope’s success also sets the stage for the upcoming Square Kilometre Array (SKA) — a next-generation radio observatory that will be even more powerful and capable of detecting faint, fast, and rare transient sources across the universe.
Key Numbers at a Glance
- 30 new radio transient pulsars detected
- 14 sources with known rotation periods (0.121 to 7.623 seconds)
- One pulsar with a long 17.5-second period detected in follow-up
- Dispersion measures from 12 to 394.4 pc/cm³
- Fluence range: 0.1–2 Jy·ms, peaking around 0.3–0.7 Jy·ms
- Nine sources localized to arcsecond precision
- Observed frequencies: 544–1,088 MHz (UHF) and 856–1,712 MHz (L-band)
- Extremely low duty cycles, suggesting narrow beams and rare bursts
The discovery of these 30 new radio transient pulsars proves that our galaxy still holds many cosmic secrets waiting to be found. With projects like MeerTRAP and upcoming instruments such as SKA, the next decade could revolutionize our understanding of how neutron stars behave, evolve, and light up the radio sky in unexpected ways.
Research Reference: Discovery of 30 Galactic radio transient pulsars with MeerTRAP (arXiv, 2025)
