How to 'listen to' the birth of black holes?
La partecipazione dell’Australia alla potenziale scoperta delle onde gravitazionali, e quindi alla capacità di “ascoltare” la nascita di un buco nero, riceverà oggi una accelerata. Questo è il giorno in cui i fisici di tutto il continenti australiano si incontreranno all’Australian International Gravitational Research Centre presso Gingin, quasi 100 Km da Perth. L’obiettivo del meeting è quello di lanciare una missione a livello nazionale che abbia lo scopo di espandere la partecipazione dell’Australia ai progetti americani ed europei unendosi così alla ricerca delle elusive perturbazioni dello spaziotempo.
Gravitational waves are ripples in the curvature of spacetime. They are thought to mark the beginning of time at the Big Bang and the end of time as black holes are born. They are generated by extreme cosmic events such as colliding stars and supernova explosions. Theory predicts that they carry vast amounts of energy at the speed of light. While their power can exceed the power of all the stars in the Universe, their effects are miniscule and difficult to detect. Centre Director, The University of Western Australia’s Winthrop Professor David Blair, said 1000 physicists around the world are currently involved in the search which is focused on the commissioning of three enormous supersensitive detectors that will start operating within the next few years in the USA and Europe, with another under construction in Japan. “The expected step in sensitivity will extend their reach tenfold and increase the number of expected signals 1000-fold“, he said. Professor Peter Veitch, Chair of the Australian Consortium for Gravitational Astronomy, said: “The new advanced detectors change the whole game. For the first time we have firm predictions: both the strength and the number of signals. No longer are we hoping for rare and unknown events. We will be monitoring a significant volume of the Universe and for the first time we can be confident that we will ‘listen’ to the coalescence of binary neutron star systems and the formation of black holes. Once these detectors reach full sensitivity we should hear signals almost once a week“. Data from the detectors will be used in conjunction with optical telescopes that will search the sky for visible signs of the catastrophic events signaled by the gravitational waves. Australia is contributing two telescopes to the search: the Zadko telescope at Gingin and the Skymapper telescope at Coonabarrabran in New South Wales. The data from the detectors will be distributed to data analysis teams in many countries. The Australian data analysis team has developed special techniques for digging signals out of the unavoidable noise in the detectors, plus special techniques that use graphics processing units for detecting signals the instant they occur (instead of traditional techniques which can take minutes or hours to identify signals). This fast detection method is especially important if optical telescopes are going to be able to locate distant explosions the moment they occur.
One of the most exciting sources is expected to be the coalescence of pairs of neutron stars to form a black hole, giving out a burst of gamma rays and a flash of light that astronomers call a kilonova.
In this project the Pawsey Centre supercomputers will be equipped with ‘search pipelines’ developed at ANU, Melbourne and UWA. These are massive computer codes designed to separate signals from the noise. Each pipeline is optimised for a specific type of signal, such as the chirps expected as neutron stars spiral together and black holes form. Using these codes, Australian students will be able to play a major role in the first discovery of gravitational waves. The project will be launched at the Gravity Discovery Centre (GDC) by the Chair of GDC Fred Deshon, the Chair of the Gravitational Wave Observatory Development Committee Jens Balkau and the Chair of the Australian Consortium for Gravitational Astronomy Peter Veitch. The GDC which also includes the Gingin Observatory shares the Gingin site with the Australian International Gravitational Research Centre and provides public education on the big questions of the Universe.