Astronomers Discover Thousands of Hidden Siblings of the Seven Sisters

Astronomers at the University of North Carolina at Chapel Hill have made a groundbreaking discovery regarding the Pleiades star cluster, commonly known as the Seven Sisters. Their research indicates that this iconic cluster represents only a small, bright center of a much larger group of related stars.

By utilizing data from NASA's Transiting Exoplanet Survey Satellite, TESS, and the European Space Agency's Gaia space telescope, the team identified thousands of additional stellar relatives dispersed across the sky.

They have termed this expansive structure the Greater Pleiades Complex, revealing that the cluster is about twenty times larger than previously believed. Stars typically form in groups, but as they age, these groups tend to disperse, complicating efforts to track their origins.

The researchers utilized stellar rotation as a 'cosmic clock,' recognizing that younger stars spin rapidly while older stars exhibit slower rotation rates. By analyzing this rotation data alongside precise measurements from the Gaia mission, the team concluded that the Pleiades is not merely a compact grouping but serves as the dense core of a larger, gradually dispersing stellar association.

Lead author Andrew Boyle stated that this study transforms our perception of the Pleiades, highlighting it as a collection of thousands of long-lost siblings scattered throughout the sky. The cultural significance of the Pleiades extends beyond astrophysics; it has been a critical reference point for understanding young stars and exoplanets and holds meaning in various cultures, from biblical references to its celebration as Matariki in New Zealand and its representation in Subaru's logo in Japan.

Co-author Andrew Mann emphasized that the findings suggest many stars near the Sun may belong to vast extended stellar families with intricate structures. The research also introduces a novel approach to mapping the Milky Way, indicating that many star clusters previously thought to be isolated might actually be part of larger stellar families.

This method could assist scientists in exploring the origins of the Sun and whether it too formed within a similarly extensive stellar group. Boyle remarked that by measuring stellar rotation, astronomers can identify groups too dispersed for traditional detection methods, thereby revealing the hidden architecture of our Galaxy.

This research contributes significantly to the understanding of how solar systems form, providing essential insights into the environments in which stars and planets are birthed and how they evolve over time.

The findings were published in The Astrophysical Journal.