Lost Sisters Found: TESS and Gaia Reveal a Dissolving Pleiades Complex

TL;DR

This paper introduces a Bayesian method combining TESS and Gaia data to identify and analyze the extended structure of the Pleiades, revealing it as part of a larger, coeval stellar complex originating from the same molecular cloud.

Contribution

The study develops a scalable Bayesian framework that integrates stellar rotation and kinematic data to trace the origins of dispersed star cluster remnants.

Findings

The Pleiades is part of a larger, 600 pc complex with a common origin.

Most stars in the complex share similar ages and elemental abundances.

The method successfully links dispersed stars to their birth events.

Abstract

Most star clusters dissolve into the Galaxy over tens to hundreds of millions of years after they form. While recent Gaia studies have honed our view of cluster dispersal, the exact chronology of which star formation events begat which star cluster remnants remains unclear. This problem is acute after 100 Myr, when cluster remnants have spread over hundreds of parsecs and most age estimates for main sequence stars are too imprecise to link the stars to their birth events. Here we develop a Bayesian framework that combines TESS stellar rotation rates with Gaia kinematics to identify diffuse remnants of open clusters. We apply our method to the Pleiades, which previous studies have noted shows kinematic similarities to other nearby young stellar groups. We find that the Pleiades constitutes the bound core of a much larger, coeval structure that contains multiple known clusters distributed over 600 pc. We refer to this structure as the Greater Pleiades Complex. On the basis of uniform ages, coherent space velocities, detailed elemental abundances, and traceback histories, we conclude that most stars in this complex originated from the same giant molecular cloud. This work establishes a scalable approach for tracing the genealogies of nearby clusters and further cements the Pleiades as a cornerstone of stellar astrophysics. We aim to apply this methodology to other associations as part of the upcoming TESS All-Sky Rotation Survey.