Twinkling star reveals the shocking secrets of turbulent plasma in our cosmic neighbourhood

Twinkling star reveals the shocking secrets of turbulent plasma in our cosmic neighbourhood

With the most powerful radio telescope in the southern hemisphere, we have observed a twinkling star and discovered an abundance of mysterious plasma structures in our cosmic neighbourhood. The plasma structures we see are variations in density or turbulence, akin to interstellar cyclones stirred up by energetic events in the galaxy. The study, published today in Nature Astronomy, also describes the first measurements of plasma layers within an interstellar shock wave that surrounds a pulsar. We now realise our local interstellar medium is filled with these structures and our findings also include a rare phenomenon that will challenge theories of pulsar shock waves.

What happens when matter is squashed to the brink of collapse? We weighed a neutron star to help NASA find out

What happens when matter is squashed to the brink of collapse? We weighed a neutron star to help NASA find out

Neutron stars are some of the most extreme objects in the universe. Formed from the collapsed cores of supergiant stars, they weigh more than our Sun and yet are compressed into a sphere the size of a city. The dense cores of these exotic stars contain matter squashed into unique states that we can't possibly replicate and study on Earth. That's why NASA is on a mission to study neutron stars and learn about the physics that governs the matter inside them. My colleagues and I have been helping them out. We used radio signals from a fast-spinning neutron star to measure its mass. This enabled scientists working with NASA data to measure the star's radius, which in turn gave us the most precise information yet about the strange matter inside.

First hints of gravitational waves from supermassive black hole pairs

First hints of gravitational waves from supermassive black hole pairs

When black holes and other enormously massive, dense objects whirl around one another, they send out ripples in space and time called gravitational waves. These waves are one of the few ways we have to study the enigmatic cosmic giants that create them. Astronomers have observed the high-frequency “chirps” of colliding black holes, but the ultra-low-frequency rumble of supermassive black holes orbiting one another has proven harder to detect. For decades, we have been observing pulsars, a type of star that pulses like a lighthouse, in search of the faint rippling of these waves. In June 2023, pulsar research collaborations around the world – including ours, the Parkes Pulsar Timing Array – announced their strongest evidence yet for the existence of these waves.

The hunt for interstellar tornadoes with twinkling pulsars

The hunt for interstellar tornadoes with twinkling pulsars

One enigmatic feature of the interstellar plasma is the presence of dense, compact, and intensely-turbulent regions, akin to an interstellar tornado. These so-called extreme scattering events, or ESEs, are poorly understood because they are difficult to study. Our current understanding is so poor that scientists would expect such extreme objects to quickly destroy themselves. How they form and how they sustain themselves is a mystery. The solution to this puzzle likely involves the magnetic fields in our Galaxy but further study of ESEs is critical. Unfortunately, ESEs are so small by astronomical standards, that they are completely invisible to other areas of astronomy.

Observing twinkling pulsars to understand mysterious interstellar plasma

Observing twinkling pulsars to understand mysterious interstellar plasma

Pulsars—rapidly-spinning remnants of stars that flash like a lighthouse—occasionally show extreme variations in brightness. Scientists predict that these short bursts of brightness happen because dense regions of interstellar plasma (the hot gas between stars) scatter the radio waves emitted by the pulsar.