Mission to the Gravitational Focus of the Sun: A Critical Analysis

TL;DR

This paper critically examines the feasibility of using the Sun's gravitational field as a large-scale lens for imaging distant exoplanets, highlighting technical challenges and deriving signal gain calculations.

Contribution

It provides a detailed analysis of the difficulties in employing the Sun as a gravitational telescope and introduces a method to calculate signal gain and magnification.

Findings

Signal gain is finite for on-axis sources of non-zero area.

Pointing and focal length challenges are significant.

Solar corona noise impacts imaging quality.

Abstract

The gravitational field of the sun will focus light from a distant source to a focal point at a minimal distance of 550 Astronomical Units from the sun. A proposed mission to this gravitational focus could use the sun as a very large lens, allowing (in principle) a large amplification of signal from the target, and a very high magnification. This article discusses some of the difficulties involved in using the sun as such a gravitational telescope for a candidate mission, that of imaging the surface of a previously-detected exoplanet. These difficulties include the pointing and focal length, and associated high magnification; the signal to noise ratio associated with the solar corona, and the focal blur. In addition, a method to calculate the signal gain and magnification is derived using the first-order deflection calculation and classical optics, showing that the gain is finite for an on-axis source of non-zero area.