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What are galaxies made of?

24 May 2016

An orange galaxy

Will stardust particles help scientists solve the mysterious of the universe? Image by shutterstock.

One of the greatest mysteries of the universe is how planets, solar systems and galaxies are formed. We may be one big step closer to solving this, thanks to new research into comet particles by UTS Professor Milos Toth and recent PhD graduate Dr Aiden Martin.

In 2006 NASA brought particles collected from the comet Wild 2 back to Earth as part of the Stardust mission. The samples were collected in a low-density silica aerogel—essentially a solid foam. This made examining the particles difficult.

With the funding of a SIEF John Stocker Postgraduate Scholarship in 2013, Dr Martin’s PhD project aimed to develop a technology to expose and analyse the cometary particles.

The research, just published in Meteoritics & Planetary Science (opens an external site), uses electron beam chemical etching to dig holes in the aerogel and expose the particles, without inadvertently damaging them in the process.  

Experimenting on materials similar to the Stardust particles and their foam encasing, the technique effectively vaporises the aerogel and exposes the comet particles. It also causes the emission of x-rays from the particles, which are then measured to find out what they are made of.

“The challenge for NASA has been how to expose these particles and not lose them or damage them in the process of doing it,” Professor Toth said.

“What's neat about the technique is that it finds where the particles are and exposes them in a way that vaporises the surrounding material but doesn't destroy the particles.

“Then we can do the measurements of the particles right there—we don't have to move it onto another system to measure them, we just dig down to the particles and measure them.”

A stardust particle before and after exposure to the light

A stardust particle before and after exposure to the light

The experiment took place in the lab of Dr Eric Silver, an astrophysicist the Harvard-Smithsonian Centre for Astrophysics. Dr Silver’s lab uses an advanced x-ray microcalorimeter in a home-made setup which provides analytical capabilities only available in a few places in the world. 

The process for exposing the comet particles was also conducted in collaboration with scientists from the University of California, the Smithsonian Institute and the Lawrence Berkeley National Laboratory.

This gave the project access to the materials used in the experiment and the expertise to design the project in order to address NASA’s concerns properly.

While the technique was designed for the Stardust project’s particles, it can also be applied to other fields where materials need to be modified at the nanoscale in order to control how they behave with light.

“The technique is like reverse 3D printing, it uses an electron beam to remove material with a high level of precision in order to make nanostructures or microstructures,” Professor Toth said.

The next stage of the research is to use the technique on the actual Stardust samples. After that, we may find out not just what comets are made of, but how the large objects in space, and even our solar system, came about.