International Pulsar Timing Array
Encyclopedia
The International Pulsar Timing Array (IPTA) is a consortium of consortia ,
comprising the European Pulsar Timing Array
(EPTA), the North American Nanohertz Observatory for Gravitational Waves
(NANOGrav), and the Parkes Pulsar
Timing Array (PPTA). The goal of the IPTA is to detect gravitational waves using an
array of approximately 30 pulsars. This goal is shared by each of the participating
consortia individually, but they have all recognized that their goal will be achieved
more quickly in collaboration, and by combining their respective resources.
The basic experiment exploits the predictability the pulses from millisecond pulsars
(MSPs) and uses them as a system of Galactic clocks. Disturbances in the clocks will
be measurable at Earth. A disturbance from a passing gravitational wave will have
a particular signature across the ensemble of pulsars, and will be thus detected.
The experiment is analogous to ground-based interferometric detectors such as
LIGO
and VIRGO
, where the time-of-flight of a laser beam is measured along a
particular path and compared to the time-of-flight along an orthogonally oriented
path. Instead of the time-of-flight of a laser beam the IPTA is measuring the time-
of-flight of an electromagnetic pulse from the pulsar. Instead of 4 km arms (as in
the case of LIGO) the ‘arms’ of the IPTA are thousands of light-years (the distance
between the pulsars and the earth.) Each of the PTAs times approximately 20
millisecond pulsars (MSPs) each month. With significant overlap between the
collaborations the total number of MSPs timed by the IPTA (and thus the number
of ‘arms’ in the detector) is approximately 30.
These differences between the IPTA and the ground-based interferometers allow
them to probe a completely different range in gravitational-wave frequency and
thus a different category of sources. Whereas ground-based detectors are sensitive
to 10’s-1000’s of Hz, the IPTA is sensitive to 10’s-100’s of microHertz. Their
primary source of gravitational waves is supermassive black-hole binaries (billions
of solar masses), presumed to exist in plenty in the universe at the centers of
galaxies, resulting from previous mergers of those galaxies.
The resources of the IPTA are substantial. The EPTA uses large quantities of
time on Europe’s five 100-meter class telescopes: the Lovell Telescope at Jodrell Bank,
England, the Effelsberg 100-m Telescope in Germany, the Sardinia Radio Telescope
in Italy, the Westerbork Synthesis Radio Telescope in the Netherlands, and the
Nancay Radio Telescope in France. Together these 5 telescopes make up the Large
European Array for Pulsars (LEAP) in which they operate together as a single 300-meter class telescope.
NANOGrav uses about 1-day per month of time at the Green Bank 100-m telescope,
and 0.5 days per month at the 300-m Arecibo observatory
in Puerto Rico. The PPTA
uses several days per month at the 64-meter Parkes Radio Telescope.
Pulsar timing was tied for top ranking in the "medium size" category for priorities
from the Particle Astrophysics and Gravitational Panel of the Astro2010 Decadal
Review sponsored by the National Academy. The table is in Table B.1 of the report.
The IPTA is coordinated and advised by the IPTA committee, a six-member
committee with two representatives from each of the three PTA consortia.
Currently on the committee are Andrea Lommen (chair, Franklin and Marshall
College), Dick Manchester (ATNF), Scott Ransom (NRAO), Ben Stappers (Jodrell
Bank Center for Astrophysics), Gilles Theureau (Nancay Telescope), and Willem van
Straten (Swinburne University). Each of the three consortia are also members of the
Gravitational Wave International Committee, an advisory council consisting of the
leaders of gravitational wave experiments worldwide.
comprising the European Pulsar Timing Array
European Pulsar Timing Array
The European Pulsar Timing Array is a European collaboration to combine five 100-m class radio-telescopes to observe an array of pulsars with the specific goal of detecting gravitational waves...
(EPTA), the North American Nanohertz Observatory for Gravitational Waves
North American Nanohertz Observatory for Gravitational Waves
The North American Nanohertz Observatory for Gravitational Waves is a consortium of astronomers who share a common goal of detecting gravitational waves via regular observations of an ensemble of millisecond pulsars using with the Green Bank and Arecibo radio telescopes...
(NANOGrav), and the Parkes Pulsar
Timing Array (PPTA). The goal of the IPTA is to detect gravitational waves using an
array of approximately 30 pulsars. This goal is shared by each of the participating
consortia individually, but they have all recognized that their goal will be achieved
more quickly in collaboration, and by combining their respective resources.
The basic experiment exploits the predictability the pulses from millisecond pulsars
(MSPs) and uses them as a system of Galactic clocks. Disturbances in the clocks will
be measurable at Earth. A disturbance from a passing gravitational wave will have
a particular signature across the ensemble of pulsars, and will be thus detected.
The experiment is analogous to ground-based interferometric detectors such as
LIGO
LIGO
LIGO, which stands for the Laser Interferometer Gravitational-Wave Observatory, is a large-scale physics experiment aiming to directly detect gravitational waves. Cofounded in 1992 by Kip Thorne and Ronald Drever of Caltech and Rainer Weiss of MIT, LIGO is a joint project between scientists at MIT,...
and VIRGO
Virgo
-Astronomy:* Virgo Cluster, a cluster of galaxies in the constellation Virgo* Virgo , a constellation* Virgo Stellar Stream, remains of a dwarf galaxy* Virgo Supercluster, a galactic supercluster-Surname:* Virgo...
, where the time-of-flight of a laser beam is measured along a
particular path and compared to the time-of-flight along an orthogonally oriented
path. Instead of the time-of-flight of a laser beam the IPTA is measuring the time-
of-flight of an electromagnetic pulse from the pulsar. Instead of 4 km arms (as in
the case of LIGO) the ‘arms’ of the IPTA are thousands of light-years (the distance
between the pulsars and the earth.) Each of the PTAs times approximately 20
millisecond pulsars (MSPs) each month. With significant overlap between the
collaborations the total number of MSPs timed by the IPTA (and thus the number
of ‘arms’ in the detector) is approximately 30.
These differences between the IPTA and the ground-based interferometers allow
them to probe a completely different range in gravitational-wave frequency and
thus a different category of sources. Whereas ground-based detectors are sensitive
to 10’s-1000’s of Hz, the IPTA is sensitive to 10’s-100’s of microHertz. Their
primary source of gravitational waves is supermassive black-hole binaries (billions
of solar masses), presumed to exist in plenty in the universe at the centers of
galaxies, resulting from previous mergers of those galaxies.
The resources of the IPTA are substantial. The EPTA uses large quantities of
time on Europe’s five 100-meter class telescopes: the Lovell Telescope at Jodrell Bank,
England, the Effelsberg 100-m Telescope in Germany, the Sardinia Radio Telescope
in Italy, the Westerbork Synthesis Radio Telescope in the Netherlands, and the
Nancay Radio Telescope in France. Together these 5 telescopes make up the Large
European Array for Pulsars (LEAP) in which they operate together as a single 300-meter class telescope.
NANOGrav uses about 1-day per month of time at the Green Bank 100-m telescope,
and 0.5 days per month at the 300-m Arecibo observatory
Arecibo Observatory
The Arecibo Observatory is a radio telescope near the city of Arecibo in Puerto Rico. It is operated by SRI International under cooperative agreement with the National Science Foundation...
in Puerto Rico. The PPTA
uses several days per month at the 64-meter Parkes Radio Telescope.
Pulsar timing was tied for top ranking in the "medium size" category for priorities
from the Particle Astrophysics and Gravitational Panel of the Astro2010 Decadal
Review sponsored by the National Academy. The table is in Table B.1 of the report.
The IPTA is coordinated and advised by the IPTA committee, a six-member
committee with two representatives from each of the three PTA consortia.
Currently on the committee are Andrea Lommen (chair, Franklin and Marshall
College), Dick Manchester (ATNF), Scott Ransom (NRAO), Ben Stappers (Jodrell
Bank Center for Astrophysics), Gilles Theureau (Nancay Telescope), and Willem van
Straten (Swinburne University). Each of the three consortia are also members of the
Gravitational Wave International Committee, an advisory council consisting of the
leaders of gravitational wave experiments worldwide.