Direct Detection of Gravity Waves through High-Precision Astrometry

Abstract

It is generally accepted that a first ever direct detection of gravity waves would herald a new era in astronomy and in fundamental physics. Ever since the early sixties, increasingly larger human and material resources are being invested in the detection effort. Unfortunately, the gravity wave effects one has had to exploit so far are extraordinarily small and are usually very many orders of magnitude smaller than the noise involved. The detectors that are presently at the most advanced stage of development hope to register extremely rare, instantaneous longitudinal shifts that are expected to be orders of magnitude smaller than one Fermi. However, it was recently shown that gravity waves can manifest themselves through much larger effects than previously envisaged. One of these new effects is the periodic, apparent shift in a star's angular position due to a foreground gravity wave source. The comparative largeness of this effect stems from its being proportional not to the inverse of the gravity wave source's distance to the Earth, but to the inverse of its distance to the star's line of sight. In certain optimal but not unrealistic cases, the amplitude of this effect can reach the critical bar of one micro-arcsecond, thus raising the prospect that the long awaited first direct detection of gravity waves could be achieved by a high precision astrometry space mission such as GAIA.