Benfords law in the Gaia universe

TL;DR

This paper investigates whether Benfords law applies to the extensive Gaia DR2 parallaxes, including negative values and Bayesian distance estimates, and explores its potential as a validation tool for Gaia data accuracy.

Contribution

It extends previous studies by analyzing a much larger dataset, including negative parallaxes, and evaluates Benfords law's applicability to Bayesian distance estimates in astronomy.

Findings

Benfords law holds for Gaia DR2 parallaxes including negatives.

Bayesian distance estimates also follow Benfords law.

Benfords law can serve as a validation tool for Gaia parallax zero-point.

Abstract

Benfords law states that for scale- and base-invariant data sets covering a wide dynamic range, the distribution of the first significant digit is biased towards low values. This has been shown to be true for wildly different datasets, including financial, geographical, and atomic data. In astronomy, earlier work showed that Benfords law also holds for distances estimated as the inverse of parallaxes from the ESA Hipparcos mission. We investigate whether Benfords law still holds for the 1.3 billion parallaxes contained in the second data release of Gaia (Gaia DR2). In contrast to previous work, we also include negative parallaxes. We examine whether distance estimates computed using a Bayesian approach instead of parallax inversion still follow Benfords law. Lastly, we investigate the use of Benfords law as a validation tool for the zero-point of the Gaia parallaxes.