Steven Detweiler

Last updated
Steven Lawrence Detweiler
Born
Died(2016-02-08)February 8, 2016
Alma mater Princeton University (B.A. 1969)
University of Chicago (Ph.D. 1976)
Known for Gravitational waves
Black holes
Pulsar timing array
Awards Fellowship of the American Physical Society
Scientific career
Fields Theoretical physics
Institutions University of Florida
Doctoral advisor James R. Ipser

Steven L. Detweiler was a theoretical physicist and professor of physics at the University of Florida best known for proposing pulsar timing arrays as a means to detect gravitational waves, [2] an idea that led to the discovery of a stochastic gravitational wave background in 2023. [3]

Contents

Background

Detweiler received his bachelor's degree from Princeton University in 1969 and his Ph.D. from the University of Chicago in 1976 under the supervision of James R. Ipser. [4] In 2013, he was elected to a fellowship of the American Physical Society in recognition of his many and varied contributions to gravitational physics. [5] [6]

Detweiler's research focused on the dynamics of stars and black holes, as well as on the production and observation of gravitational waves. In 1975 together with Subrahmanyan Chandrasekhar, Detweiler calculated the effects of fluctuations on black holes. [7] This is important for understanding the stability of black holes, as well as the later stages of the dynamics of black hole mergers. In 1979, Detweiler proposed the idea of a pulsar timing array to measure gravitational waves with wavelengths on the scale of light-years. [2] This built upon an earlier proposal by Mikhail Sazhin to use individual pulsars. [8] The idea was first taken up experimentally by Foster and Backer in 1990, [9] and today globally there are five active pulsar timing array experiments. In 2023, this idea led to the discovery of a stochastic gravitational wave background by the NANOGrav experiment and other pulsar timing array experiments. [3]

Related Research Articles

<span class="mw-page-title-main">General relativity</span> Theory of gravitation as curved spacetime

General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations.

The following is a timeline of gravitational physics and general relativity.

<span class="mw-page-title-main">Laser Interferometer Space Antenna</span> European space mission to measure gravitational waves

The Laser Interferometer Space Antenna (LISA) is a planned space probe to detect and accurately measure gravitational waves—tiny ripples in the fabric of spacetime—from astronomical sources. LISA will be the first dedicated space-based gravitational-wave observatory. It aims to measure gravitational waves directly by using laser interferometry. The LISA concept features three spacecraft arranged in an equilateral triangle with each side 2.5 million kilometers long, flying in an Earth-like orbit heliocentric orbit. The distance between the satellites is precisely monitored to detect a passing gravitational wave.

<span class="mw-page-title-main">Pulsar</span> Rapidly rotating neutron star

A pulsar is a highly magnetized rotating neutron star that emits beams of electromagnetic radiation out of its magnetic poles. This radiation can be observed only when a beam of emission is pointing toward Earth, and is responsible for the pulsed appearance of emission. Neutron stars are very dense and have short, regular rotational periods. This produces a very precise interval between pulses that ranges from milliseconds to seconds for an individual pulsar. Pulsars are one of the candidates for the source of ultra-high-energy cosmic rays.

<span class="mw-page-title-main">Millisecond pulsar</span> Pulsar with a rotational period less than about 10 milliseconds

A millisecond pulsar (MSP) is a pulsar with a rotational period less than about 10 milliseconds. Millisecond pulsars have been detected in radio, X-ray, and gamma ray portions of the electromagnetic spectrum. The leading hypothesis for the origin of millisecond pulsars is that they are old, rapidly rotating neutron stars that have been spun up or "recycled" through accretion of matter from a companion star in a close binary system. For this reason, millisecond pulsars are sometimes called recycled pulsars.

Tests of general relativity serve to establish observational evidence for the theory of general relativity. The first three tests, proposed by Albert Einstein in 1915, concerned the "anomalous" precession of the perihelion of Mercury, the bending of light in gravitational fields, and the gravitational redshift. The precession of Mercury was already known; experiments showing light bending in accordance with the predictions of general relativity were performed in 1919, with increasingly precise measurements made in subsequent tests; and scientists claimed to have measured the gravitational redshift in 1925, although measurements sensitive enough to actually confirm the theory were not made until 1954. A more accurate program starting in 1959 tested general relativity in the weak gravitational field limit, severely limiting possible deviations from the theory.

The gravitational wave background is a random background of gravitational waves permeating the Universe, which is detectable by gravitational-wave experiments, like pulsar timing arrays. The signal may be intrinsically random, like from stochastic processes in the early Universe, or may be produced by an incoherent superposition of a large number of weak independent unresolved gravitational-wave sources, like supermassive black-hole binaries. Detecting the gravitational wave background can provide information that is inaccessible by any other means about astrophysical source population, like hypothetical ancient supermassive black-hole binaries, and early Universe processes, like hypothetical primordial inflation and cosmic strings.

This timeline lists significant discoveries in physics and the laws of nature, including experimental discoveries, theoretical proposals that were confirmed experimentally, and theories that have significantly influenced current thinking in modern physics. Such discoveries are often a multi-step, multi-person process. Multiple discovery sometimes occurs when multiple research groups discover the same phenomenon at about the same time, and scientific priority is often disputed. The listings below include some of the most significant people and ideas by date of publication or experiment.

<span class="mw-page-title-main">Gravitational wave</span> Propagating spacetime ripple

Gravitational waves are waves of the intensity of gravity that are generated by the accelerated masses of binary stars and other motions of gravitating masses, and propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as the gravitational equivalent of electromagnetic waves. Gravitational waves are sometimes called gravity waves, but gravity waves typically refer to displacement waves in fluids. In 1916 Albert Einstein demonstrated that gravitational waves result from his general theory of relativity as ripples in spacetime.

<span class="mw-page-title-main">Gravitational-wave observatory</span> Device used to measure gravitational waves

A gravitational-wave detector is any device designed to measure tiny distortions of spacetime called gravitational waves. Since the 1960s, various kinds of gravitational-wave detectors have been built and constantly improved. The present-day generation of laser interferometers has reached the necessary sensitivity to detect gravitational waves from astronomical sources, thus forming the primary tool of gravitational-wave astronomy.

<span class="mw-page-title-main">Gravitational-wave astronomy</span> Branch of astronomy using gravitational waves

Gravitational-wave astronomy is a subfield of astronomy concerned with the detection and study of gravitational waves emitted by astrophysical sources.

<span class="mw-page-title-main">Donald C. Backer</span> American astrophysicist

Donald Charles Backer was an American astrophysicist who primarily worked in radio astronomy. Backer made important contributions to the understanding and study of pulsars, black holes, and the epoch of reionization.

<span class="mw-page-title-main">Primordial black hole</span> Hypothetical black hole formed soon after the Big Bang

In cosmology, primordial black holes (PBHs) are hypothetical black holes that formed soon after the Big Bang. In the inflationary era and early radiation-dominated universe, extremely dense pockets of subatomic matter may have been tightly packed to the point of gravitational collapse, creating primordial black holes without the supernova compression typically needed to make black holes today. Because the creation of primordial black holes would pre-date the first stars, they are not limited to the narrow mass range of stellar black holes.

A pulsar timing array (PTA) is a set of galactic pulsars that is monitored and analysed to search for correlated signatures in the pulse arrival times on Earth. As such, they are galactic-sized detectors. Although there are many applications for pulsar timing arrays, the best known is the use of an array of millisecond pulsars to detect and analyse long-wavelength gravitational wave background. Such a detection would entail a detailed measurement of a gravitational wave (GW) signature, like the GW-induced quadrupolar correlation between arrival times of pulses emitted by different millisecond pulsar pairings that depends only on the pairings' angular separations in the sky. Larger arrays may be better for GW detection because the quadrupolar spatial correlations induced by GWs can be better sampled by many more pulsar pairings. With such a GW detection, millisecond pulsar timing arrays would open a new low-frequency window in gravitational-wave astronomy to peer into potential ancient astrophysical sources and early Universe processes, inaccessible by any other means.

<span class="mw-page-title-main">European Pulsar Timing Array</span> Five-radio telescope collaboration to track stellar remnants gravitational waves

The European Pulsar Timing Array (EPTA) 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. It is one of several pulsar timing array projects in operation, and one of the four projects comprising the International Pulsar Timing Array, the others being the Parkes Pulsar Timing Array, the North American Nanohertz Observatory for Gravitational Waves, and the Indian Pulsar Timing Array.

The North American Nanohertz Observatory for Gravitational Waves (NANOGrav) is a consortium of astronomers who share a common goal of detecting gravitational waves via regular observations of an ensemble of millisecond pulsars using the Green Bank Telescope, Arecibo Observatory, the Very Large Array, and the Canadian Hydrogen Intensity Mapping Experiment (CHIME). Future observing plans include up to 25% total time of the Deep Synoptic Array 2000 (DSA2000). This project is being carried out in collaboration with international partners in the Parkes Pulsar Timing Array in Australia, the European Pulsar Timing Array, and the Indian Pulsar Timing Array as part of the International Pulsar Timing Array.

The International Pulsar Timing Array (IPTA) is a multi-institutional, multi-telescope collaboration comprising the European Pulsar Timing Array (EPTA), the North American Nanohertz Observatory for Gravitational Waves (NANOGrav), the Parkes Pulsar Timing Array (PPTA) in Australia, and the Indian Pulsar Timing Array Project (InPTA). The goal of the IPTA is to detect ultra-low-frequency gravitational waves, such as from mergers of supermassive black holes, using an array of approximately 30 pulsars. This goal is shared by each of the participating institutions, but they have all recognized that their goal will be achieved more quickly by combining their respective efforts and resources.

<span class="mw-page-title-main">First observation of gravitational waves</span> 2015 direct detection of gravitational waves by the LIGO and VIRGO interferometers

The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016. Previously, gravitational waves had been inferred only indirectly, via their effect on the timing of pulsars in binary star systems. The waveform, detected by both LIGO observatories, matched the predictions of general relativity for a gravitational wave emanating from the inward spiral and merger of a pair of black holes of around 36 and 29 solar masses and the subsequent "ringdown" of the single resulting black hole. The signal was named GW150914. It was also the first observation of a binary black hole merger, demonstrating both the existence of binary stellar-mass black hole systems and the fact that such mergers could occur within the current age of the universe.

<span class="mw-page-title-main">Chiara Mingarelli</span> Italian-Canadian astrophysicist

Chiara Mingarelli is an Italian-Canadian astrophysicist who researches gravitational waves. She is an assistant professor of physics at Yale University since 2023, and previously an assistant professor at the University of Connecticut (2020–2023). She is also a science writer and communicator.

<span class="mw-page-title-main">Hellings-Downs curve</span> Gravitational wave detection tool

The Hellings-Downs curve is an analytical tool that helps to find patterns in pulsar timing data in an effort to detect long wavelength gravitational waves. More precisely, the Hellings-Downs curve refers to the wave-like shape predicted to appear in a plot of timing residual correlations versus the angle of separation between pairs of pulsars. This theoretical correlation function assumes a gravitational wave background that is isotropic and Einsteinian.

References

  1. "Steven Lawrence Detweiler, Legacy Obituary". Legacy.com . Retrieved 2024-01-05.
  2. 1 2 Detweiler, Steven L. (1979). "Pulsar timing measurements and the search for gravitational waves". Astrophys. J. 234: 1100. Bibcode:1979ApJ...234.1100D. doi:10.1086/157593.
  3. 1 2 NANOGrav (2023). "The NANOGrav 15 yr Data Set: Evidence for a Gravitational-wave Background". Astrophys. J. Lett. 951 (1): L8. arXiv: 2306.16213 . Bibcode:2023ApJ...951L...8A. doi: 10.3847/2041-8213/acdac6 .
  4. "Steven L. Detweiler, Inspire" . Retrieved 2024-01-05.
  5. "Steven Detweiler". Physics Today. 2016. doi:10.1063/PT.5.6205 . Retrieved 15 May 2024.
  6. "APS Fellowships". American Physical Society. Retrieved 15 May 2024.
  7. Chandrasekhar, S.; Detweiler, S. (1975). "The quasi-normal modes of the Schwarzchild black hole". Proc. Roy. Soc. Lond. A. 344 (1639): 441–452. Bibcode:1975RSPSA.344..441C. doi:10.1098/rspa.1975.0112.
  8. Sazhin, Mikhail V. (1978). "Opportunities for detecting ultralong gravitational waves". Sov. Astron. 22: 36–38. Bibcode:1978SvA....22...36S.
  9. Foster, R.S.; Backer, D.C. (1990). "Constructing a pulsar timing array". Astrophysical Journal . 361: 300–308. Bibcode:1990ApJ...361..300F. doi:10.1086/169195.