Direct determination of astronomical distances and proper motions by interferometric parallax

Abstract

Aims. We discuss a new method for measuring the distances to astronomical objects and their transverse proper velocities.

Methods. The phenomenon of interferometric parallax identifies a component of 2- and 4-point amplitude and the intensity correlations that can be observed at frequencies ranging from radio to optical. The calculation hinges on terms depending on the source to receiver separation that are conventionally neglected in the Van Cittert-Zernicke theorem.

Results. Order of magnitude estimates find that the baselines of Earth-bound VLBI systems might be capable of measuring 10-100 kpc distance scales. In either the optical or radio regime, space-borne detectors with fine baseline control might resolve source distances of Gigaparsec order. We discuss the possibility that an independent distance ladder based directly on experimental measurement might be constructed on multiple scales.