New Test Of General Relativity Research Articles

Life, the universe and everything, with GAIA

Great things are expected of the GAIA Observatory, currently expected to launch in 2011. Gerry Gilmore explains how it will provide accurate measurements that will help us understand the formation of the Milky Way and the distribution of dark matter. The GAIA Observatory, ESA’s Cornerstone 6 mission, addresses the origin and evolution of our galaxy, and a host of other scientific challenges. GAIA will provide unprecedented positional and radial velocity measurements with the accuracies needed to produce a stereoscopic and kinematic census of about one billion stars in our galaxy and throughout the Local Group, about 1% of the galactic stellar population. Combined with astrophysical information for each star, provided by on-board multicolour photometry, these data will have the precision and depth necessary to address the three key questions which underlie the GAIA science case: l when did the stars in the Milky Way form? l when and how was the Milky Way assembled? l what is the distribution of dark matter in our galaxy? The accurate stellar data acquired for this purpose will also have an enormous impact on all areas of stellar astrophysics, including luminosity calibrations, structural studies, and the cosmic distance scale. Additional scientific products include detection and orbital classification of tens of thousands of extrasolar planetary systems, a comprehensive survey of objects ranging from huge numbers of minor bodies in our solar system, including near-Earth objects, through galaxies in the nearby universe, to some 500 000 distant quasars. GAIA will also provide several stringent new tests of general relativity and cosmology.

The Confrontation between General Relativity and Experiment

The status of experimental tests of general relativity and of theoretical frameworks for analysing them are reviewed. Einstein’s equivalence principle (EEP) is well supported by experiments such as the Eötvös experiment, tests of special relativity, and the gravitational redshift experiment. Future tests of EEP and of the inverse square law will search for new interactions arising from unification or quantum gravity. Tests of general relativity at the post-Newtonian level have reached high precision, including the light defl ection the Shapiro time delay, the perihelion advance of Mercury, and the Nordtvedt effect in lunar motion. Gravitational wave damping has been detected in an amount that agrees with general relativity to half a percent using the Hulse-Taylor binary pulsar, and new binary pulsar systems may yield further improvements. When direct observation of gravitational radiation from astrophysical sources begins, new tests of general relativity will be possible.

Deflection of spacecraft trajectories as a new test of general relativity.

We derive a simple formula which gives the general relativistic deflection of a spacecraft, idealized as a point mass, for all values of the asymptotic speed V(infinity) (0< or =V(infinity)< or =1). Using this formula we suggest a new test of general relativity (GR) which can be carried out during a proposed interstellar mission that involves a close pass of the Sun. We show that, with foreseeable improvements in spacecraft tracking sensitivity, the deflection of a spacecraft's trajectory in the gravitational field of the Sun could provide a new test of GR.

GAIA: Composition, formation and evolution of the Galaxy

The GAIA astrometric mission has recently been approved as one of thenext two ``cornerstones'' of ESA's science programme, with a launch datetarget of not later than mid-2012. GAIA will provide positional andradial velocity measurements with the accuracies needed to produce astereoscopic and kinematic census of about one billion stars throughoutour Galaxy (and into the Local Group), amounting to about 1 percent ofthe Galactic stellar population. GAIA's main scientific goal is toclarify the origin and history of our Galaxy, from a quantitative censusof the stellar populations. It will advance questions such as when thestars in our Galaxy formed, when and how it was assembled, and itsdistribution of dark matter. The survey aims for completeness to V=20mag, with accuracies of about 10 mu as at 15 mag. Combined withastrophysical information for each star, provided by on-boardmulti-colour photometry and (limited) spectroscopy, these data will havethe precision necessary to quantify the early formation, and subsequentdynamical, chemical and star formation evolution of our Galaxy.Additional products include detection and orbital classification of tensof thousands of extra-Solar planetary systems, and a comprehensivesurvey of some 105-106 minor bodies in our SolarSystem, through galaxies in the nearby Universe, to some 500 000 distantquasars. It will provide a number of stringent new tests of generalrelativity and cosmology. The complete satellite system was evaluated aspart of a detailed technology study, including a detailed payloaddesign, corresponding accuracy assesments, and results from a prototypedata reduction development. (Less)

Sources of gravitational radiation: Coalescing binaries

Binaries consisting of compact objects — neutron stars, or black holes — seem likely to become the source of gravitational radiation most frequently observed in the late 1990's by the ground-based, laser-interferometric detectors now under development. The radiation comes from the orbital motion as the stars spiral together due to gravitational radiation reaction. The low frequencies observable from space make new classes of binaries detectable, such as coalescing massive black holes, and make it possible that several coalescencing systems with relatively long times to coalescence could be detected in our own galaxy. I examine the prospects for detecting such sources with various types of space-based detectors, and then consider the sorts of things we could learn from them, including new tests of general relativity.

Higher-order relativistic periastron advances and binary pulsars

The contributions to the periastron advance of a system of two condensed bodies coming from relativistic dynamical effects of order higher than the usual first post-Newtonian (1PN) equations of motion are investigated. The structure of the solution of the orbital second post-Newtonian (2PN) equations of motion is given in a simple parametrized form. The contributions to the secular periastron advance, and to the period, of orbital 2PN effects are then explicitly worked out by using the Hamilton-Jacobi method. The spin-orbit contribution to the secular precession of the orbit in space is rederived in a streamlined way by making full use of Hamiltonian methods. These results are then applied to the theoretical interpretation of the observational data of pulsars in close eccentric binary systems. It is shown that the higher-order relativistic contributions are already of theoretical and astrophysical significance for interpreting the high-precision measurement of the secular periastron advance of PSR 1913+16 achieved by Taylor and coworkers. The case of extremely fast spinning (millisecond) binary pulsars is also discussed, and shown to offer an easier ground for getting new tests of general relativity, and/or, a direct measurement of the moment of inertia of a neutron star.

On a new gravitational effect of a rotating mass

A new general relativistic many-body effect is described. It results in an unexpectedly large relative acceleration between neighboring test particles that follow an inclined orbit about a rotating mass. The effect vanishes if the orbit coincides with the equatorial plane of the rotating mass. The existence of this effect is due to a small divisor involving the deviation of the orbital frequency measured by a comoving clock from the frequency measured by an inertial clock. The influence of the rotation of the Sun on the Earth-Moon system is investigated, and it is shown that the new effect causes a harmonic variation in the Earth-Moon separation with an amplitude of order 1 m and dominant periods of 18.6 yr, ∼1/2 yr, 1 month, and ∼1/2 month. The confirmation of these results by the lunar laser ranging experiment would provide a significant new test of general relativity and a measurement of the angular momentum of the Sun.

A new test of general relativity - Gravitational radiation and the binary pulsar PSR 1913+16

view Abstract Citations (587) References (37) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS A new test of general relativity - Gravitational radiation and the binary pulsar PSR 1913+16 Taylor, J. H. ; Weisberg, J. M. Abstract Pulse arrival times of a binary pulsar were observed for seven years using average pulse profiles representing about five minutes of data acquisition with synchronous averaging and a least squares procedure for fitting the standard profiles. A model was formulated using relativistic terms, both secular and periodically varying with orbital phase, and it was assumed that the pulsar is an accurate clock. Tests were made to determine the magnitude of possible systematic biases. The component masses and absolute size of the orbit were determined. These values were used, together with the well-determined orbital period and eccentricity, to calculate the rate at which the orbital period should decay as energy is lost from the system via gravitational radiation. The results agreed strikingly with general relativity but disagreed with most other theories of gravitation. For this reason, the companion star must be a neutron star or black hole. Publication: The Astrophysical Journal Pub Date: February 1982 DOI: 10.1086/159690 Bibcode: 1982ApJ...253..908T Keywords: Binary Stars; Gravitational Waves; Orbit Calculation; Pulsars; Pulsed Radiation; Relativity; Black Holes (Astronomy); Error Analysis; Least Squares Method; Neutron Stars; Orbit Decay; Stellar Mass; Stellar Models; Stellar Motions; Stellar Radiation; Physics (General) full text sources ADS | data products SIMBAD (1)

A new test of general relativity

The emission of gravitational radiation by the recently discovered binary pulsar system will cause its orbital periodP to decrease at a rate which can now be predicted to beP−1dP/dt= −(3 ± 2) × 10−9yr−1 if the only orbital perturbations are of general-relativistic origin. It is shown that other sources of period change are probably less important. The accuracy of this prediction as well as the possibility of its verification will improve greatly over the next few years. This is the first observation that can test general relativity beyond the post-Newtonian approximation.

New Test of General Relativity: Preliminary Results

New Test of General Relativity: Preliminary Results

The Problem of the Rotating Disk

In Part I of this paper, the spatial geometry of the surface of a rotating disk is examined from the standpoint of general relativity theory. Eddington's argument for a homaloidal surface is shown to be in error, and Einstein's "relative" geometry is correlated with the "intrinsic" geometry of the disk (i.e., the geometry as determined by an observer at rest on the rotating disk). The Gaussian measure of hypercurvature of the surface, at any point on the disk at radius $r$ is found to be $\ensuremath{-}3\frac{{\ensuremath{\omega}}^{2}}{{c}^{2}}{(1\ensuremath{-}\frac{{\ensuremath{\omega}}^{2}{r}^{2}}{{c}^{2}})}^{\ensuremath{-}2}$. In Part II, the temporal aspects of the rotating disk are examined and a new test of general relativity, by use of the cyclotron, is proposed: an artificially radioactive element of low atomic weight is revolved, as ions, within the cyclotron. Upon being brought to rest, the element should be found more radioactive than an equivalent sample of that element remaining at rest.