Building $100m black hole detector ‘not pie in the sky’
“You cannot create conditions like that in the lab; you could never hope to. This is how we can study matter at its most extreme in the universe.”
The detector, known as NEMO, is one of nine recommendations made in the Decadal Plan for Australian Astronomy mid-term review, released publicly on Wednesday by the Australian Academy of Science’s National Committee for Astronomy.
The report was sent to the federal government several weeks ago.
“It’s not just pie in the sky. It’s things we do definitely want to do. It’s a plan, not an aspiration,” said University of Queensland astronomer Professor Tamara Davis, one of the report’s authors.
Science Minister Karen Andrews said she was considering the report’s expert advice.
“Participation in an Australian gravitational wave observatory … would need to be taken in the context of Australia’s considerable investments and scientific involvement in multinational astronomical facilities more generally,” she said, pointing to federal investments in the sprawling Square Kilometre Array in Western Australia and the Giant Magellan Telescope in Chile.
A separate paper led by OzGrav and Monash University and published on Wednesday lays out NEMO’s design specifications: two arms, each four kilometres long which would be used to detect gravitational waves coming from the neutron star collisions.
The project would cost between $50 and $100 million and would be complete by the late 2020s. The team has not yet selected a preferred site for the project.
Gravitational waves are ripples in the fabric of space-time. They are one of the most radical – yet accurate – predictions of Albert Einstein’s general theory of relativity.
Einstein imagined space-time as a sheet of elastic. Heavy objects, such as stars, weigh down the sheet.
Extremely heavy and fast-moving objects, such as neutron stars, cause ripples in the sheet that spread out through the universe. When they pass through the Earth, they slightly stretch and shrink our space-time (yes, you are being stretched and shrunk too, if only very slightly).
Gravitational wave detectors pick up these ripples by using huge straight tubes which can be several kilometres long. A laser is used to measure the distance between the ends of the tubes to within a fraction of the size of an atom.
When a gravitational wave passes through the detector, the arms shrink and expand slightly – a difference picked up by the laser.
Astronomers’ current detectors are very good at detecting gravitational waves made by colliding black holes. But before neutron stars collide, they orbit extremely quickly around each other, creating gravitational waves at a frequency too high for current detectors to study.
NEMO would be purpose-built to pick up and study those collisions.
But the astronomers behind the project also have a second, even more ambitious goal.
The global astronomy community has long-term plans to build three much larger, 40 kilometre-long $1.5 billion gravitational wave detectors dotted around the planet, including one in the southern hemisphere.
NEMO would allow many of the new technologies needed for those detectors to be tested and put Australia in pole position when it came to deciding where they would be built.
“Much of the science demands three detectors distributed around the world, and we think there’s a niche in building a prototype to watch neutron stars tearing each other apart,” said Professor Matthew Bailes, director of OzGrav.
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Liam is The Age and Sydney Morning Herald’s science reporter