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Australian Student Astronomer Finds Universe's Missing Mass

May 29th 2011

Science - Blue sphere in space

An Australian student at Monash University has made a breakthrough in the field of astrophysics, discovering what has until now been described as the Universe’s ‘missing mass.’ Amelia Fraser-McKelvie, working as a member of a team at the Monash School of Physics, conducted a targeted X-ray search for the matter and within just three months found it – or at least some of it.

What makes the discovery all the more noteworthy is the fact that Fraser-McKelvie is not a career researcher, or even studying at a postgraduate level. She is a 22-year-old undergraduate Aerospace Engineering/Science student who pinpointed the missing mass during a summer scholarship, working with two astrophysicists at the School of Physics, Dr. Kevin Pimbblet and Dr. Jasmina Lazendic-Galloway.

The School of Physics put out a call for students interested in a six-week paid astrophysics research internship during a recent vacation period, and chose Ms Fraser-McKelvie from a large number of applicants. Dr. Pimbblet, lecturer in the School of Physics put the magnitude of the discovery in context by explaining that scientists had been hunting for the Universe’s missing mass for decades.

"We've been looking for this ordinary matter for a couple of decades," said Dr. Pimbblett. "It's been published in one of the most prestigious journals in the world, so astronomers all over the world will be able to read this article." Predicting that the discovery may change the way telescopes are built, the astronomer said "We will be using this as part of the science drivers for some telescopes that are on the design board, that are being built right at this moment in time," he said.

Not since the work of Fritz Zwicky has the astronomy world been so excited about the missing mass of the Universe. Zwicky's evidence came from observing the orbital velocities of galaxies in clusters, rotational speeds, and gravitational lensing of background objects. Fraser-McKelvie's breakthrough in the world of astrophysics may verify Zwicky's findings. Born in Switzerland, Zwicky spend most of career at California Technological University, where he made advances in both observational and theoretical astronomy.

“It was thought from a theoretical viewpoint that there should be about double the amount of matter in the local Universe compared to what was observed.  It was predicted that the majority of this missing mass should be located in large-scale cosmic structures called filaments - a bit like thick shoelaces,” said Dr. Pimbblet.

Astrophysicists also predicted that the mass would be low in density, but high in temperature - approximately one million degrees Celsius. This meant that, in theory, the matter should have been observable at X-ray wavelengths. Amelia Fraser-McKelvie’s discovery has proved that prediction correct.

Fraser-McKelvie said the ‘Eureka moment’ came when Dr. Lazendic-Galloway closely examined the data they had collected.  “Using her expert knowledge in the X-ray astronomy field, Jasmina reanalysed our results to find that we had in fact detected the filaments in our data, where previously we believed we had not.” She added, "I feel really lucky."

X-ray observations provide important information about physical properties of large-scale structures, which can help astrophysicists better understand their true nature. Until now, they had been making deductions based only on numerical models, so the discovery is a huge step forward in determining what amount of mass is actually contained within filaments.

Still a year away from undertaking her Honors year (which she will complete under the supervision of Dr. Pimbblet), Fraser-McKelvie is being hailed as one of Australia’s most exciting young students.  Her work has been published in one of the world’s oldest and most prestigious scientific journals, the Monthly Notices of the Royal Astronomical Society.

“Being a published author is very exciting for me, and something I could never have achieved without the help of both Kevin and Jasmina. Their passion and commitment for this project ensured the great result and I am very thankful to them for all the help they have given me and time they have invested,” said Fraser-McKelvie.

Dr. Pimbblet said that Fraser-McKelvie is very talented student who excelled in performing the breakthrough research. “She has managed to get a refereed publication accepted by one of the highest ranking astronomy journals in the world as a result of her endeavours.  I cannot underscore enough what a terrific achievement this is. We will use this research as a science driver for future telescopes that are being planned, such as the Australian Square Kilometre Array Pathfinder, which is being built in outback Western Australian.” The paper can be found at the Cornell University website.http://arxiv.org/abs/1104.0711

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