Posted by David Kaplan on March 30, 2015
The NANOGrav PFC will address a transformational challenge in astrophysics: the detection of low-frequency gravitational waves.
Gravitational waves are elusive ripples in the fabric of space-time, which theories predict should arise from extremely energetic and large-scale cosmic events, such as orbiting pairs of massive black holes found at the centers of merging galaxies, phase transitions in the very early universe, or as relics from cosmic inflation, the period just after the Big Bang when all of the universe that we can see expanded rapidly from a minuscule volume in a tiny fraction of a second.
In Einstein's theory of gravity, these events produce waves that distort, or ripple, the actual fabric of the cosmos as they emanate throughout space. The waves have such a long wavelength—significantly larger than our solar system—that we cannot build a detector large enough to observe them.
Fortunately, the universe itself has created its own detection tool—millisecond pulsars—the rapidly spinning, super-dense remains of massive stars that have exploded as supernovas. These ultra-stable stars are nature’s most precise celestial clocks, appearing to 'tick' every time their beamed emissions sweep past the Earth like a lighthouse beacon.
Gravitational waves may be detected in the small but perceptible fluctuations—a few tens of nanoseconds over five or more years—they cause in the measured arrival times at Earth of radio pulses from these millisecond pulsars.
NANOGrav was founded in 2007 and, at the time, consisted of 17 members in the United States and Canada. It has since grown to 55 scientists and students at 15 institutions. The NANOGrav PFC will provide funding for 23 senior personnel, 6 postdoctoral researchers, 10 graduate students, and 25 undergraduate students distributed across 11 institutions.
Xavier Siemens, a physicist at the University of Wisconsin-Milwaukee, is the Principal Investigator for the project and will serve as director of the center. Maura McLaughlin, an astronomer at West Virginia University, will serve as co-director.
NSF currently supports nine other PFCs, which range in research areas from theoretical biological physics and the physics of living cells to quantum information and nuclear astrophysics.
By bringing together astronomers and physicists from across the United States and Canada to search for the telltale signature of gravitational waves buried in the incredibly steady ticking of distant pulsars, NANOGrav is advancing the PFC mission to "foster research at the intellectual frontiers of physics" and to “enable transformational advances in the most promising research areas.”
"NANOGrav is now poised to detect low-frequency gravitational waves," said Siemens. "This Center will ensure that researchers have the resources necessary to explore one of the most exciting frontiers in all of physics and astronomy."
This research makes use of the unique capabilities and sensitivity of the Arecibo Observatory in Puerto Rico and the National Radio Astronomy Observatory's Green Bank Telescope (GBT). The GBT is located in the National Radio Quiet Zone, which protects the incredibly sensitive telescope from unwanted radio interference, enabling it to study pulsars and other astronomical objects. Arecibo is the largest single dish radio telescope in the world today.
"NANOGrav is fortunate to have access to the two most sensitive telescopes in the world for this groundbreaking research," McLaughlin said. "Furthermore, as many of our observations are performed by students, the telescopes are serving a vital role in creating a pipeline for science and technology fields."
"This is a really exciting time to work on the search for gravitational waves," said David Kaplan, UWM associate professor of physics and a participant on the grant. "We are optimistic that gravitational waves will be detected by 2020, which would be the culmination of decades of hard work by dozens of astronomers."
The Physics Frontier Center ensures that UWM students, both graduate and undergraduate, will play a vital role in the search for gravitational waves, he added. The research performed by the PFC is distributed among the participating institutions and members of NANOGrav.
[Image credit: David Champion (MPIfR), NAIC, NRAO]