Amrita Banerjee

PhD student
CDM
Swinburne University of Technology
Road-tripping in Tasmania in 2026

How would you describe your work to a 10-year old?

You know how stars live together in huge groups called galaxies, like cities made of billions of stars? Most galaxies are busy making brand-new baby stars all the time. But some of them just stop, forever. We call those dead galaxies, and I want to understand why they die.

Here’s the cool part. Every galaxy is wrapped in a giant invisible blob of stuff we can’t see, called dark matter. You can’t see it or touch it, but its gravity holds the whole galaxy together, like an invisible hand cupping a handful of glitter. My big question is: how heavy is that invisible blob? You can’t put a galaxy on a scale, so I use a detective trick. The heavier the invisible blob, the more likely galaxies are to clump together. So I count how clumped-up they are and work backward to figure out the weight.

But how do I know my trick really works? I build a pretend universe inside a giant computer, one where I already know the right answer, and test my trick on it first. If it works there, I can trust it in the real sky. And the best bit: the galaxies I study are so far away that their light took billions of years to reach us, so I’m really looking back in time. I’m basically a time-travelling detective, weighing invisible giants in a universe I can rewind.

How did you get to where you are today?

I chose physics because of the night sky. All those stars made me wonder what they were and how everything out there began, and I have been chasing those answers ever since.

I did my Master’s in physics, specialising in cosmology and particle physics (the largest and smallest scales in the universe). During that, I worked on something called AGN.

Right at the centre of most galaxies sits a black hole, usually fast asleep. But sometimes it wakes up, and that hungry, glowing centre is an AGN, like the most powerful lighthouse in the universe, powered by a black hole’s dinner. I was a detective figuring out what wakes the black hole up and makes it feed, and how to tell these galaxies apart from normal ones, which glow simply because they are busy making new baby stars.

Now I’m doing my PhD at Swinburne, studying enormous galaxies that died far earlier than anyone expected.

What advice would you give to someone considering studying physics/science?

My advice is simple: stay curious about everyday things. Physics is not locked away in textbooks or labs; it is everywhere, in why the sky is blue, how a bike stays upright, and why your tea goes cold. If you already find yourself wondering how ordinary things work, you have exactly what science needs.

What do you enjoy doing outside of work/besides physics?

Outside of physics, I love reading books, choreographing dance, travelling a lot, writing poems, theatre and watching different types of films

Which three people (living or dead) would you invite to dinner?

Rabindranath Tagore
Richard Feynman
“You know who”