A network of pulsars being used to search for gravitational waves, or ripples in space-time predicted by general relativity. These waves cause changes in the arrival times of pulsar radio signals that are correlated between pulsars in a way that depends on their separation on the sky. They are detectable from Earth with sensitive radio timing observations. Credit: David Champion.
The NSF's Robert C. Byrd Green Bank Telescope, which will join in the NANOGrav hunt for gravitational waves.
Credit: NRAO/AUI/NSF
Credit: NRAO/AUI/NSF
An animation demonstrating interacting supermassive black holes in merging galaxies and how this generates low frequency gravitational waves. As these waves propagate through space, they cause coordinated changes in the arrival times of radio signals from pulsars, the universe’s most stable natural clocks, as seen from Earth. These telltale variations can be detected by powerful radio telescopes, like the Arecibo Observatory in Puerto Rico and the Green Bank Telescope in West Virginia.
Credit: John Rowe, Swinbourne
The National Science Foundation (NSF) has awarded the North American
Nanohertz Observatory for Gravitational Waves (NANOGrav) $14.5 million
over 5 years to create and operate a Physics Frontiers Center (PFC).
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 propagate throughout space. These
low-frequency 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, superdense
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 in
Morgantown, 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.”
“For
pulsar astronomers to be able to detect these gravitational waves, we
really need the best and most sensitive radio telescopes in the world,”
said Scott Ransom, an astronomer with the National Radio Astronomy
Observatory (NRAO) in Charlottesville, Va., and one of the founding
members of NANOGrav. “In the United States, we have the two best -- the
Green Bank Telescope in West Virginia with its fantastic sky coverage
and the Arecibo Observatory in Puerto Rico with its unmatched
sensitivity. These instruments have given us a huge edge in this
research.”
“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 NRAO’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 stated. “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.”
The
National Radio Astronomy Observatory is a facility of the National
Science Foundation, operated under cooperative agreement by Associated
Universities, Inc.
# # #
Contact:
Charles Blue
NRAO Public Information Officer
(434) 296-0314; cblue@nrao.edu
The research performed by the PFC is distributed among the participating institutions and members of NANOGrav. The personnel funded by the NANOGrav PFC include:
California Institute of Technology
Curt Cutler
Joseph Lazio
Walid Majid
Michele Vallisneri
Cornell University
James Cordes
Rachel Bean
Adam Brazier
Shamibrata Chatterjee
Franklin and Marshall College
Andrea Lommen
Fronefield Crawford
Lafayette College
David Nice
Montana State University
Neil Cornish
Universities Space Research Association and NASA’s Goddard Space Flight Center
Zaven Arzoumanian
National Radio Astronomy Observatory
Paul Demorest
Scott Ransom
Oberlin College
Daniel Stinebring
University of Texas at Brownsville
Fredrick Jenet
Joseph Romano
University of Wisconsin–Milwaukee
David Kaplan
Xavier Siemens
West Virginia University
Duncan Lorimer
Maura McLaughlin
Sean McWilliams
They collaborate closely with Ingrid Stairs at the University of British Columbia in Vancouver, Canada, and Victoria Kaspi at McGill University in Montreal, Canada.
