This book aims to communicate the basic logic of interferometric gravitational wave detectors to students who are new to the field. Many people will want to understand more about what a gravitational wave is, how LIGO works, and how LIGO functions as a detector of gravitational waves. “This is just the beginning of our work,” Siemens said.LIGO's recent discovery of gravitational waves was headline news around the world. NANOGrav researchers say future studies of the signals super-massive black holes send out will enable scientists to view the gravitational wave universe through a new window, offering insight into titanic black holes merging in the centers of distant galaxies and potentially into other exotic sources of low-frequency gravitational waves. Super-massive black holes are the biggest type of black holes, millions to billions of times the mass of the sun, and they reside in the centers of galaxies. “We want to hear the collective chorus of all of the super-massive black hole binaries that are merging in the universe.” “Each signal is like a note, and we’re not just after one of these notes – we want to hear the whole choir,” he said. Siemens explains that using a PTA to detect a chorus of gravitational wave signals from multiple super-massive black hole mergers – described as a stochastic background of gravitational waves – holds more promise for understanding the universe than detecting a single wave from a single black hole binary collision.
“NANOgrav searches for gravitational waves with frequencies 11 orders of magnitude below those LIGO is detecting,” he said.
The gravitational waves that can be observed by LIGO, created by those types of “black hole binaries,” have frequencies of about 100 hertz, Hazboun said. Researchers with LIGO, also an NSF-funded international collaboration, in 2015 detected gravitational waves produced by the collision of two black holes using the twin LIGO interferometers in Livingston, Louisiana, and Hanford, Washington. “These results are made possible through the National Science Foundation’s continued commitment to these exceptionally sensitive radio observatories.” “Pulsars are actually very faint radio sources, so we require thousands of hours a year on the world’s largest telescopes to carry out this experiment,” McLaughlin said. Morton and other OSU undergraduates contribute by searching for new pulsars to add to NANOGrav’s array the more pulsars at its disposal, the more sensitive the gravitational wave detection can be, she explains. On the contrary, large-scale science projects require enormous amounts of collaboration and for everyone involved to believe in the goals of the group.” “It is a common misconception that scientific breakthroughs come from a lone genius. “Searching for gravitational waves is like putting together a puzzle: Everyone has their own piece but they all fit together,” said Phia Morton of Bend, a senior majoring in applied physics and nuclear engineering. Siemens said OSU receives about $600,000 annually in NANOGrav funding, with data analysis being Oregon State’s primary role in addition to project leadership and administration.Ĭo-directed by Maura McLaughlin, an astronomer at West Virginia University, NANOGrav combines the efforts of researchers at 18 universities, including approximately 20 graduate and undergraduate students at Oregon State. Siemens joined OSU in 2019 and two years later the NSF awarded NANOGrav an additional $17 million over five years to search for gravitational wave signals with the Green Bank Telescope in West Virginia, the Very Large Array in New Mexico and the Arecibo Observatory in Puerto Rico. NANOGrav began in 2007 and eight years later launched as a Physics Frontier Center with a $14.5 million grant from the National Science Foundation when Siemens was at the University of Wisconsin-Milwaukee. “We can use those pulsars as clocks spread out through the sky, and we can see how the ticking of the clocks changes from gravitational waves passing through our galaxy.” “The large number of pulsars used in the NANOGrav analysis has enabled us to see what we think are the first signs of the correlation pattern predicted by general relativity,” Siemens said. Einstein’s 1915 theory of general relativity predicted how gravitational waves should affect pulsar signals: By stretching and squeezing the fabric of time-space, gravitational waves should alter the timing of each pulse in a predictable way, delaying some pulses while speeding up others.
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