In the most powerful radio telescope in the southern hemisphere, we observed a twinkling star and discovered a large number of mysterious plasma structures in our cosmic community.
The plasma structure we see is a change in density or turbulence, similar to the interstellar cyclone of interstellar cyclones, as energy events in galaxies stir up.
The study was published in Natural Astronomythe first measurement of the plasma layer in the interstellar shock wave surrounding the pulsar is also described.
Now that we realize that our local interstellar medium is filled with these structures, our findings also include a rare phenomenon that will challenge pulsar radio wave theory.
Pulsar and its shock waves
Our observations were conducted on nearby fast spin Pulsar, J0437-4715, 512 light years from Earth. Pulsars are neutron stars, a super-intensive stellar residue that produces radio waves and particles of “wind”.
Pulsars and their winds move at supersonic speeds in interstellar medium (the things between stars (gas, dust, and plasma). This creates a bow-shaped shock: the shock wave of the heating gas emits red.
Interstellar plasma is turbulent, with scattered pulsar radio waves slightly away from direct straight line paths. The scattered waves create a bright and dim patch pattern that drifts on our radio telescopes as the Earth, pulsars and plasma all move in space.
From our perspective, this causes pulsars to flicker or “flash”. The effect is similar to how turbulent flows in the Earth’s atmosphere make the stars flash in the night sky.
Pulsar flicker gives us unique information about the plasma structure being too small and weak to detect in other ways.
A flashing little radio star
To the naked eye, the flickering of the star may appear random. But at least for pulsars, there are hidden patterns.
Using the right technique, we can find ordered shapes from interference patterns, called scintillation arcs. They detail the position and velocity of compact structures in interstellar plasma. Studying a scintillation arc is like performing a CT scan of an interstellar medium, each arc displaying a thin layer of plasma.
Often, scintillation arc studies find only one or at most only a few arcs, and only appreciate the most extreme (the densest or most turbulent) plasma structures in our galaxy.
Our scintillation arc study reveals an unprecedented 25 scintillation arc, which is the new basis for the most plasma structure observed by any pulsar to date.
The sensitivity of our study is only due to the sensitivity outside of the close range of the pulsar (our closest millisecond bean neighbor) and the large collection area of the Meerkat range telescope in South Africa.
Local bubble surprise
Of the 25 flashing arcs we found, 21 reveal structures in interstellar mediums. This is surprising because like our own solar system, Pulsar is located in a relatively quiet area of our galaxy called local bubbles.
About 14 million years ago this part of our galaxy was illuminated by star explosions that swept through the material in the interstellar medium and expanded the thermal void. Today, this bubble is still expanding, now up to 1,000 light-years away.
Our new flash arc discovery shows that the local bubble is not as empty as previously thought. It is full of compact plasma structures that can only last until the bubbles cool at least in some areas, dropping from millions to 10,000 degrees Celsius.
Shocked discovery
The pulsar surrounds its bow, which shocks and emits red from the light that energizes atoms.
While most pulsars are thought to produce bow impacts, only a few are observed to be faint objects. So far, no research has been used to use flicker.
We trace the remaining four scintillation arcs to the plasma structure in Pulsar Bow Shock, marks the first time astronomers stare at one of these shock waves.
This provides us with a CT-like field of view similar to different plasma layers. Using these arcs with optical images, we construct a new three-dimensional impact model that appears to deviate from us due to the movement of pulsars through space.
The flashing arc also provides us with the speed of the plasma layer. We found that an internal plasma structure is flowing towards the impact line in the opposite direction.
Although such reverse flows can occur in simulations, they are rare. This discovery will drive the new model of this bow vibrating.
The science of flickering
With new and more sensitive radio telescopes built around the world, we can expect to see more of the Pulsar Bow Shocks in interstellar medium and other events to see flickering in other events.
This will discover more about the energy processes in our galaxy that create these otherwise invisible plasma structures.
The flickering of this pulsar neighbor shows the unexpected plasma structure inside the local bubble, allowing us to map and measure the plasma velocity in the bow impact. What a twinkling little star can do is amazing.
Daniel Reardon is a postdoctoral researcher for pulsar timing and gravitational waves at Swinburne University of Technology. This article is from dialogue.
publishing – May 13, 2025 at 06:00 AM IST
