New field of astrophysics is answering questions about the origins of the Universe

Where do galaxies come from? Did they start off really small? How did they become the monsters we see today? How does gravity work near black holes?

Our Gravitational Wave Group is hoping to answer such questions in their quest to seek the truths of the Universe. Dr Andrew Lundgren, our Reader in Gravitational Wave Science, is part of this group. He’s using gravitational waves, a new area of astrophysics, to see the Universe in a totally different way.

Created when black holes or neutron stars collide, gravitational waves are unstoppable. As they travel through space, they spread out. By the time they reach Earth they’re incredibly tiny. This makes it nearly impossible to detect these waves. 

It’s taken decades of work fine-tuning gravitational wave detectors to make the impossible possible. Before the first gravitational waves were detected, in 2015, there was no direct proof they existed. It was all theoretical up to that point. Not any more. 

 

Listening to the Universe

Andrew explains:

‘We’ve only started making a lot of progress in the last couple of years. We’re now getting a sense of what the life cycle of stars is. Not just in our galaxy but very far out. We’re using two 4km long detectors, that are like gigantic microphones, to detect colliding black holes and neutron stars.’

Gravitational waves make mirrors in the detector vibrate at levels smaller than the size of an atom. It’s extraordinarily subtle stuff. Initially, these waves were detected at the rate of around one a month. Increasing sensitivity means this has risen to about one a week. 

Andrew says:

‘Gravitational waves move fast but the frequencies are a lot lower than light. So you can actually hear them.  

‘We’re listening out for the last moments of dead stars coming together about a billion light years away. When this happens, the sound propagates through space time and ripples in space. And these instruments pick it up.’

What does it sound like?

‘It sounds remarkably like a bird chirping!’

Challenging the accepted

Andrew wants to push the boundaries of Einsten’s theory of gravity. 

‘Einstein’s theory is perfect. It has no flaws. But black holes push at space-time and so push this theory to the limits of what it can do. And we’re hoping to find some evidence of what’s beyond this.

‘How does gravity really work? And then make a single theory of physics so it just encompasses everything.  It’s the big goal in the field.’

Andrew has great hopes for the future:

‘As we build better detectors I want to see how galaxies form. When they form they have gigantic black holes in their centre.  We don’t really know where those come from. When galaxies merge, their black holes have to merge too, but we can’t pick that up right now.’ 

These questions could be answered when LISA (Laser Interferometer Space Antenna) launches in the 2030s. Andrew hopes this spacecraft will enable him to see galaxies coming together and their black holes merging. 

‘And then,’ he says, ‘We will be able to see the entire history of the Universe.’