Predicting Our Fate With Extragalactic Exploration

Georgia Hartzenberg is on a mission to understand the physical processes that govern galaxies far, far away — back to when the universe was about 1.5 billion years old.

Hartzenberg is a postgraduate student studying astrophysics, a popular undergraduate study area at QUT where opportunities for research degrees have recently emerged.

She is investigating 60,000 galaxies to determine the role of environment in the evolution and ultimate fate of galaxies.

“The lifetime and evolution of a galaxy depends on the type of environment it resides in, but one of the many mysteries in astrophysics is how different galaxies came into existence,” Hartzenberg said.

Previous research, according to Hartzenberg, suggests it’s because of galaxy environments — activity between a galaxy’s dust and gas with its surroundings, as well as interactions with other galaxies.

“It’s been established galaxies take a variety of shapes which can reveal a lot about their properties,” Hartzenberg said.

“Galaxies that are ‘alive’ have high star formation rates and are typically spiral-shaped. Dead galaxies have low star formation and are generally elliptical.

“Isolated galaxies free from environmental interactions are usually spiral. They are left to evolve and die naturally once they finish their supply of gas and dust.

“Cluster galaxies experience more severe environmental interactions, ultimately causing them to die sooner, while galaxies that merge will share resources and delay the dying phase through prolonged star formation.”

One such environmental interaction is a phenomenon known as Ram Pressure Stripping, where galaxies travelling in a cluster are subjected to strong winds that can remove dust and gas.

“The severity of this effect is dependent on the galaxy’s velocity. A galaxy moving at 1000 km/s is likely to undergo more severe Ram Pressure Stripping than a galaxy travelling at 400 km/s,” Hartzenberg said.

“If it’s moving slowly, it may be able to restore its shape and medium, but a fast-moving galaxy is unlikely to recover and may transition from having a disk-like morphology into an elliptical.”

While current research has focused on nearby galaxies, little attention has been paid to more distant galaxies, according to Hartzenberg.

“Existing environmental research shows that our Milky Way galaxy will eventually merge with our nearest neighbour, the Andromeda Galaxy, but that won’t happen for billions of years yet.

“Ultimately, I’m trying to fill the gap in galaxy environment research by finding out what happened to much younger, distant galaxies, not just the galaxies closest to Earth.

“We are trying to understand how the universe and everything in it behaves in order to understand how to improve our world.”

The finite speed of light allows astronomers to peer into the past. When observing the most distant galaxies, Hartzenberg will see them as they were billions of years ago when the universe itself was also young.

Hartzenberg will analyse data from the recently released ZFOURGE survey of galaxies that formed when the universe was between two and 10 billion years old and includes data from many telescopes including the Magellan Telescope and Hubble Space Telescope.

But, observing these distant galaxies will make her analysis challenging.

“Astrophysics research predominantly relies on light as it is the primary connection between us and the universe,” Hartzenberg said.

“As we venture into the more distant parts of the universe, telescopes cannot identify the type of galaxies we’re observing — distant galaxies just look like pinpricks in the sky.

“Because they are further away, they are dimmer which in turn makes it difficult to obtain a quality measurement of their light.”

Hartzenberg will apply mathematical and computational methods to determine the galaxy environments and physical properties of her survey sample.

“Star formation gives us a way to monitor and identify the evolutionary stages of galaxies,” Hartzenberg said.

“I’ll compare the size and mass of galaxies, analyse their star formation rates, luminosities, ultraviolet and infrared light and their optical colours.

“Galaxies that appear ‘blue’ are typically very active in terms of star formation and primarily host young hot stars.

“Galaxies that appear ‘red’ predominately comprise much older stars and are not taking part in much star formation, so they are essentially dying.

“Therefore, the blue arms of a spiral galaxy are the parts that support star formation while the red nucleus consists of older dying stars. Elliptical galaxies appear redder so are mostly inactive.

While her findings may be some years away, Hartzenberg said she was thrilled by the opportunity to contribute to fundamental research and work with observations made by previous scientists like Edwin Hubble and Albert Einstein.

Ground-breaking tech from astrophysics research

Much of astrophysics research is purely exploratory and fundamental according to Hartzenberg ‘s supervisor, Dr Michael Cowley, but the opportunities for spin-off technology, understanding and science were inconceivable.

“Einstein was probably not thinking about GPS satellites in the early 1900s, but his theory of general relativity is a major component of our use of this technology today,” said Cowley, an astrophysicist with QUT’s School of Chemistry and Physics.

“Fundamental astrophysics research has historically led to ground-breaking enabling technologies.

“There’s been a tonne of spin-off technologies from astrophysics research, including medical equipment, Wi-Fi and computing.”

While real-world applications are a selling point for fundamental research, Cowley said astrophysics research is about exploring the world around us — not limiting ourselves to what is right in front of us but knowing how we came to be, and what’s in store for our universe.

“It’s important for us to learn important things about how our world operates, how our solar system operates, how the sun works and what solar weather is doing to us, the impact on power grids and our astronauts on the International Space Station,” Cowley said.

“By understanding these fundamental physics, we can start applying it to solve important challenges.”

Data scientists are in demand

After spending the next two years analysing extragalactic environments, Hartzenberg plans to round-out her career experience by spending time in industry as a data scientist or financial analyst.

Cowley, who previously worked in banking, said taking up careers in data science was common for astrophysicists.

“A professional astronomer or astrophysicist these days rarely looks through telescopes anymore. They do statistical analysis on data while the telescopes mostly look after themselves.

“Astronomy and astrophysics build strong skills in data science, mathematics, physics in general, and in communicating complex science to the public, which is also important.

“My astrophysics students are highly sought-after because of these transferrable skills, particularly in data science.

“Data science as an industry is growing rapidly because of our need to understand big data during large-scale events like pandemics and financial crises.”

Cowley said although there were more positions for data scientists, there were still good opportunities to become a professional astronomer.

“Australia has plenty of research facilities which are expanding, including the Square Kilometre Array– SKA — planned to be built in Australia and South Africa to create the largest ever radio telescope network.”

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