Gravitational Wave Scattering From the Sun and Planets

TL;DR

This paper calculates gravitational wave scattering by the Sun and planets, predicting a small amplitude modulation in LISA observations, which could be detectable during specific alignments over LISA's operational lifetime.

Contribution

It provides the first detailed calculation of gravitational wave tails from the Sun and planets and assesses their potential impact on LISA observations.

Findings

Scattering from the Sun and planets could cause a 10^{-3} amplitude modulation in LISA data.

Backward scattering results agree with previous long-wavelength limit calculations.

Potential for detecting gravitational wave tails during planetary alignments within LISA's mission duration.

Abstract

General relativity predicts that massless waves should scatter from the Riemann curvature of their backgrounds. These scattered waves are sometimes called $\textit{tails}$ and have never been directly observed. Here we calculate the gravitational waves scattered in the backward direction (scattering angle $\vartheta=\pi$) from the weak-field curvature of an extended massive object, finding close agreement with previous results in the long-wavelength limit. These long-wavelength results are then applied to gravitational waves in the Laser Interferometer Space Antenna (LISA) sensitivity band scattering from the Sun and planets. We estimate that scattering from the Sun and the planets from Jupiter to Neptune could contribute a $10^{-3}$ amplitude modulation to LISA observations when these objects almost intersect the line of sight between LISA and the source, leading to forward scattering with $\vartheta\simeq0$. These conditions should be realized for the Sun during the lifetime of LISA if the detection rate of long-duration sources is not much smaller than a thousand per year.