SydneySCIENCE Highlights

Field of vision: adventures in astronomy

In a world where seeing is believing, it’s hard to comprehend the size of the objects that hold the secrets of our beginnings. From the astronomically large to infinitesimally small, physicists extend their field of vision beyond the everyday, to the night skies and to the building blocks of matter.

Professor Geraint Lewis studies the formation of smaller and younger galaxies. Galactic cannibalism is an integral process in the formation of these galaxies: as clumps of matter collide they become larger, exert greater gravitational force and grow faster. Contrary to what was traditionally thought, the Milky Way will continue to grow and eventually collide with the Andromeda galaxy in what will be the largest and most dramatic event of galactic cannibalism.

Lewis uses sophisticated computational modelling to study these enormous cannibals. “We can change the dynamics of expansion, tweak the influence of inflation, or alter the properties of matter to create an infinite set of infant universes, each maturing differently.” Lewis and team then compare each of these models with our own galaxy to elucidate the fundamental properties of our cosmos.

These large scale simulations, modelling the movements of 10 billion particles over 10 billion years in as little as 3 months, will help Lewis test theories about dark matter, star formation and shed light on the processes that lead to the formation of the Milky Way.

Lewis’ models are driven mainly by predictions of the behaviour of dark matter. Dark matter, observable only through its gravitational effect, may be less complicated than stars and gases, which collide, collapse, change temperatures and fragment. Hopefully with increases in the power of supercomputers the influence of dark matter will become clearer.

Masses in our Universe behave like lenses bending and magnifying light with their gravitational field. “We can use this phenomenon to observe structures we normally couldn’t see at all. Using gravitational microlensing, where light is bent around smaller masses, we can zoom in on previously unobservable phenomena, such as quasars,” explains Lewis. But this magnification comes with considerable distortions and, much like a fairground mirror, removing these distortions is a huge computational problem. “As cosmologists, it is our task to weave together the enormous amount of data into a coherent picture of our Universe, from its formation to present day.”

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