NANOGrav in Brief

What do we do?
We seek to measure gravitational waves--ripples in space-time--by detecting their effect on radio wave signals traveling from pulsars--rapidly rotating neutron stars--to the Earth. Our measurements are most sensitive to gravitational waves with periods of a few years, which corresponds to frequencies of a few nanohertz--hence the "NANO" in our name, "NANOGrav." The strongest sources of such gravitational waves are likely to be binary systems in which two massive black holes orbit one another. Such binary systems form when galaxies merge with one another.
Who are we?
We are a collaboration of observational and theoretical astrophysicists from more than a dozen universities, colleges, and observatories. We include faculty, scientific staff, postdoctoral scholars, graduate students, and undergraduate students, and high school students.
How will we do it?
Pulsars are rapidly rotating stars. A pulsar emits beams of radio waves which, like lighthouse beams, sweep through the sky as the pulsar rotates. The signal from a pulsar can be detected by radio telescopes as a series of regularly spaced pulses, essentially like the ticks of a clock. In fact, for the purposes of this experiment, it's useful to think of the pulsars as clocks. Gravitational waves affect the time it takes the pulses to travel from the pulsar to a telescope on Earth. We seek out perturbations due to gravitational waves in measurements of pulse arrival times at a telescope, in other words, we look for deviations in the clock ticks! In particular, we search for a distinct pattern of correlation and anti-correlation between the signals over an array of different pulsars (a "pulsar timing array"). Although pulsar pulses travel through space for hundreds or thousands of years to reach us, we are sensitive to perturbations in their travel time of much less than a millionth of a second. We seek out ways to improve our sensitivity to gravitational waves, including discovering more pulsars, improving instrumentation at telescopes, studying the characteristics of pulsars and the interstellar medium which affect our measurements, and developing new algorithms for detection gravitational waves.
Where do we observe?
We collect pulsar data using two extremely sensitive North American radio telescopes. We use the Arecibo Observatory in Arecibo, Puerto Rico, the largest telescope in the world, to observe pulsars with declinations between 0 and 38 degrees. We use the Green Bank Telescope in Green Bank, West Virginia, the largest fully-steerable single-dish telescope in the world, to observe pulsars not visible from Arecibo at declinations higher than -45 degrees. We are part of the International Pulsar Timing Array (IPTA) which is a collaboration of NANOGrav with similar European and Australian counterparts. The IPTA overall uses 9 of the world's largest radio telescopes to accomplish gravitational wave detection. We collaborate with astrophysicists elsewhere to take advantage of other telescope resources worldwide.
Why do we do it?
Throughout human history, all the information we have received from outside our own solar system has come in the form of electromagnetic waves (light, radio, X-rays, etc.). Gravitational wave astronomy will give us an entirely new spectrum with which to observe the universe. The gravitational wave regime probed by pulsar timing (nanohertz) is complementary to those probed by ground detectors such as LIGO (kilohertz) and by proposed space missions (millihertz). The separation in frequency between these instruments is the comparable to the separation between radio, optical, and gamma rays in the electromagnetic spectrum. Each technique for detecting gravitational waves promises exciting, unique science.
When will we detect gravitational waves?
We envision ourselves as an ongoing (a decade or longer ) enterprise with detection occurring on a decadal timescale. Our present program is already providing unique constraints on gravitational waves from in-spirals of supermassive black holes, cosmic strings, and other sources. Our pulsar timing array presently consists of 35 pulsars, and it grows by several pulsars a year as we discovery new, high quality millisecond pulsars. We anticipate that growth in the population of pulsars under observation, improvements in telescope sensitivity through recently commissioned instrumentation, and lengthening of data sets on all pulsar sources will bring our detection levels into the range of predicted amplitudes for the stochastic background of gravitational waves within a few years.

NSF-AST Portfolio Review Response

Gravitational waves (GWs) are ripples in space-time that are known to exist but have not yet been detected directly. Once they are, a key feature of any viable theory of gravity will be demonstrated and a new window on the universe opened. GW astronomy was named as one of five key discovery areas in the “New Worlds and New Horizons” Decadal Report. Pulsar timing probes GW frequencies, and hence source classes, that are inaccessible to any other detection method and can uniquely constrain the nonlinear nature of General Relativity. Pulsar timing is therefore a critical capability with its own discovery space and potential. Fulfilling this capability requires the complementary enabling features of both the Green Bank Telescope (GBT) and the Arecibo Observatory.

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NANOGrav on Tour

Upcoming Talks


February 25, 2013
Scott Ransom will give a colloquium talk at Brown University entitled "Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars"
March 27, 2013
Scott Ransom will give seminar at Virginia Tech entitled "Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars"
April 04, 2013
Scott Ransom will give a colloquium talk at the Harvard-Smithsonian CfA ITC entitled "Neutron Star Masses and Basic Physics Consequences"

Past Talks


February 13, 2013
Scott Ransom gave a talk entitled "Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars" at the U. Penn Physics Colloquium / Rittenhouse Lecture
February 7, 2013
Scott Ransom gave a talk entitled "Detecting Gravitational Waves (and doing other cool physics) with Millisecond Pulsars" at the Montana State Physics Colloquium
October 18, 2012
Vicky Kaspi gave a talk entitled "Searching for Radio Pulsars: Big Work for Big Payoff" at Purdue University
October 16, 2012
Joe Lazio spoke on "Gravitational Wave Study via Pulsars" at the NASA Goddard Space Flight Center
October 12, 2012
Justin Ellis gave a seminar entitled "Using Pulsars to Detect Gravitational Waves" at University of Wisconson Milwaukee
October 3, 2012
Paul Demorest spoke on "Detecting gravitational waves with millisecond pulsars" at the University of Vermont Physics Department.
September 13, 2012
Vicky Kaspi gave a talk entitled "Searching for Radio Pulsars: Big Work for Big Payoff" at CITA in Toronto, Candada

NANOGrav was well represented at the IAU General Assembly in Beijing, China August 20 - 31. This is what you missed:

August 20, 2012 11:15
Ryan Lynch will speak on "The hunt for new pulsars with the Green Bank Telescope"
August 21, 2012 10:30
Sarah Burke-Spolaor will speak on "RRATs and other high-B pulsars"
August 22, 2012 11:10
David Nice will give a talk on "Neutron-star masses"
August 22, 2012 17:00
Justin Ellis will speak on "Stochastic and continuous gravitational wave analysis pipelines for PTA data"
August 22, 2012 17:15
WeiWei Zhu will speak on "19 years of high precision timing of the millisecond pulsar J1713+0747"
August 23, 2012 14:00
Jim Cordes will give a talk entitled "Galactic structure and turbulence from pulsar observations: Results and implications
August 23, 2012 16:00
Duncan Lorimer will speak on "The Galactic neutron-star population"
August 23, 2012 17:00
Shami Chatterjee will speak on "Science with radio pulsar astrometry"
August 24, 2012 8:30
Scott Ransom will be giving a plenary presentation for the Neutron Stars and Pulsars program entitled "Pulsars are cool -- Seriously"
August 24, 2012 12:15
Walid Majid will speak on "A multi-wavelength campaign to study giant pulses from the Crab pulsar"
August 24, 2012 14:40
Vicky Kaspi will inform us about "The NuSTAR and GEMS X-ray telescopes"
June 10-14, 2012
Sarah Burke-Spolaor will speak on "Exploring Dual and Binary AGN via Radio Emission" at the American Astronomical Society Meeting in Anchorage, Alaska
May 17, 2012
Jim Cordes and Sam Finn will speak on pulsar timing for gravitational wave detection in a special session at the Gravitational Wave Advanced Detector Workshop, held at the Waikoloa Marriott Resort, Hawaii
May 14, 2012
Scott Ransom will speak on "Testing General Relativity with Pulsar Timing" at the "Testing General Relativity with Astrophysical Systems Conference", held at Harvard University
May 1, 2012
Scott Ransom will speak at the Ohio State University Physics Department Colloquium
April, 11 2012
Scott Ransom will speak at the Caltech Astronomy Department Colloquium
March 31, 2012
Andrea Lommen will speak on "Pulsar Timing Arrays: No Longer a Blunt Instrument for Gravitational Wave Detection" at the American Physical Society Meeting in Atlanta, Georgia
March 29, 2012
Andrea Lommen will speak on "Pulsar Timing Arrays: No Longer a Blunt Instrument for Gravitational Wave Detection" at the University of Florida (Gainesville)
March 29, 2012
Scott Ransom will speak on ""Nuclear Physics at Two Kiloparsecs with Millisecond Pulsars"" at the Penn State Physics Department Colloquium