LIVE: Secret star stuff Natasha Hurley-Walker

It was this choice that led Natasha to detect a repeating signal from space that just shouldn't be there. 

That signal came in the form of radio emission from within our galaxy, appearing every 18.18 minutes - the slowest repetition rate ever detected. 

Quickly determined not to be aliens, but flashes of radio light from an unknown form of neutron star, this newest mystery from space is called a Long Period Radio Transient. Now, scientists are finding more and more of them with radio telescopes all over the world.

Hearing any astronomer or quantum physicist talk about these transients outlines the exciting possibilities they open up for our understanding of the Universe and atomic physics. They also make us ask, is anything really impossible?

In astronomy, transients are objects in our Universe that flash or change the light they emit over time (transient is also the lifestyle of many post-docs). 

A type of neutron star, called a pulsar, is one of the most common transients studied by radio astronomers. Discovered by Dame Jocelyn Bell Burnell in 1967, pulsars are the remains of stars that have gone supernova: exploding at the end of their life, only to leave a very small, dense ball of matter spinning incredibly quickly. The extreme environment of these pulsars causes beams of radio light to form at their north and south poles. It's these beams that we can detect from Earth.  

Because they are spinning so fast, these beams sweep across the Earth at the rate of milliseconds. One of the most famous pulsars, Vela, spins at 11 times per second.

The speed of this rotation matches what we understand on the relationships between density, gravity and atomic forces. Something spinning much, much slower makes no sense at all - it can't be explained by existing models and mathematics.

Images:

An artist's impression of a pulsar. Credit: Mark Garlick/Science Photo Library 

Some antennas of the Murchison Widefield Array (MWA). Credit: ICRAR/Dragonfly Media

Natasha has also led a project to make the best radio-image of our sky. Using the Murchison Widefield Array (MWA), a telescope operated by an international consortium and located in Western Australia, she produced an iridescent image that illuminates what had gone unseen in our own galaxy. 

The resulting image is the Galactic and Extra-Galactic All-Sky MWA Survey (GLEAM). The creation of this is so much more than just pointing a telescope at the sky and printing an image, the way an optical telescope would. With radio telescopes, these things are a bit more involved. 

As Natasha says, 

"Making this image took millions of CPU [Computer Processing Unit] hours on very powerful supercomputers. And part of the reason for that is that this area [our galaxy] is so incredibly complicated. There's bubbles around exploded stars, there's diffuse stuff, there's huge magnetic fields - it's really expensive to image that."  

But, as she points out, this is the area where we can see stuff change - where we can monitor for unusual transient activity. So once you've got all the constants mapped out, discoveries can be made.

Radio light can show us things invisible to our own eyes and help identify complex processes happening in space. For example, a radio telescope reveals the extreme forces taking place in nearby galaxy, Centaurus A, telling us that a huge black hole sits at its centre.

Image:  Centaurus A, a galaxy with a supermassive black hole, imaged at radio wavelengths with the MWA telescope. Credit: Ben McKinley, ICRAR/Curtin and Connor Matherne, Louisiana State University. 

The discovery came because Natasha got to play with the data: she had time and resources to push the boundaries of convention and look for the impossible. This is a rare opportunity in any field, but so important as we look to expand human knowledge.

This turned out to be the first of many discoveries. Three years later, astronomers are even detecting these pulsar-like objects rotating every 6 hours, deepening the mystery with every new discovery. 

For Natasha, this project was fun, it was playful, and it turned out to have huge ramifications. It told us that how we understand the Universe, stars and matter at its most extreme is incomplete.  

To solve the mystery of these transients, Natasha says she has reached the bounds of her expertise. Telescopes in other wavelengths (optical, infrared, x-ray, gamma) will need to observe these objects too, with particle physicists analysing the data to seek an explanation.

So, for now, long period radio transients stand as a reminder that there's so much more to learn. Who knows what further discoveries will tell us about our own existence and the matter that makes us. 

Image: 

 The Galactic and Extra-Galactic All-Sky MWA Survey (GLEAM). Credit: Natasha Hurley-Walker