Astrometric jitter of the sun as a star

TL;DR

This study quantifies the Sun's astrometric jitter over 11 years, revealing its correlation with solar activity and implications for detecting Earth-like exoplanets via astrometry.

Contribution

It provides detailed measurements of solar astrometric jitter and analyzes its dependence on solar activity, informing exoplanet detection strategies.

Findings

Astrometric jitter standard deviations are 0.52 μAU (equatorial) and 0.39 μAU (axial).

Jitter correlates strongly with the solar cycle, peaking at 0.91 μAU during maximum activity.

Planet detection prospects are unaffected by Sun-like star jitter, but more active stars pose challenges.

Abstract

The daily variation of the solar photocenter over some 11 years is derived from the Mount Wilson data reprocessed by Ulrich et al. 2010 to closely match the surface distribution of solar irradiance. The standard deviations of astrometric jitter are 0.52 $\mu$AU and 0.39 $\mu$AU in the equatorial and the axial dimensions, respectively. The overall dispersion is strongly correlated with the solar cycle, reaching $0.91 \mu$AU at the maximum activity in 2000. The largest short-term deviations from the running average (up to 2.6 $\mu$AU) occur when a group of large spots happen to lie on one side with respect to the center of the disk. The amplitude spectrum of the photocenter variations never exceeds 0.033 $\mu$AU for the range of periods 0.6--1.4 yr, corresponding to the orbital periods of planets in the habitable zone. Astrometric detection of Earth-like planets around stars as quiet as the Sun is not affected by star spot noise, but the prospects for more active stars may be limited to giant planets.