Astronomers from the University of North Carolina at Chapel Hill (USA) published research in the journal The Astrophysical Journal indicating that the well-known Pleiades cluster, or Messier 45 (M45), is just the dense core of a much larger stellar structure. The study points out that the group of stars popularly called the “Seven Sisters” is about 20 times larger than previously assumed. The discovery, based on data from NASA’s TESS and ESA’s Gaia satellites, reveals the “Great Pleiades Complex”, a stellar association in the process of slowly dispersing through space.
The identification was possible thanks to a new methodological approach that uses stellar rotation as an age indicator. The method allowed scientists to track thousands of stars spread across the sky, but which share a common origin and, therefore, the same age. The cluster, visible to the naked eye, now gains a new scientific and historical dimension, changing the traditional perception of this celestial object.
Related Star Tracking
The study combined precise motion and position measurements from the Gaia telescope with rotation data from the Transiting Exoplanet Survey Satellite (TESS). Astronomer Andrew Boyle, lead author of the research, highlighted that the team combined this information to reconstruct the stellar lineage. The extended structure of the cluster, now called the Greater Pleiades Complex, covers a much larger area of the sky than the central cluster.
The new technique exploits the principle that younger stars rotate at a faster speed than older ones, providing a highly reliable indicator of stellar age. This difference in rotation made it possible to identify members that formed simultaneously, even if, over time, they moved significantly apart. The researchers believe this finding could redefine understanding of the formation and dispersion of stellar associations.
The Pleiades complex and its extension
The Greater Pleiades Complex encompasses thousands of stars with common characteristics that extend across a vast celestial region, far beyond the known “Seven Sisters”. This fact suggests that what was observed as a cluster is, in fact, a looser association in an advanced stage of disaggregation. The research provides a new insight into the dynamics of stellar families, which are born together and gradually separate over billions of years.
The use of data from TESS, aimed at hunting for exoplanets, together with the detailed mapping of Gaia, resulted in a powerful tool for reconstructing cosmic lineages. Study co-author Andrew Mann hypothesizes that many stars close to the Sun, invisible in previous studies, may also be part of larger stellar families. Understanding these groups is fundamental to unraveling the primordial environments where stars and planets, and potentially the Sun itself, were born.
Implications for cosmology
The discovery has significant implications for understanding the stellar history of our galaxy. The new view of the Pleiades, not as a compact group but as thousands of scattered “lost sisters,” offers a model for studying how massive stellar associations form and dissipate. The rotation method allows us to deepen our knowledge of stellar evolution.
The cultural and historical relevance of the Pleiades, which are referenced in ancient texts, in the Talmud, and celebrate the Maori New Year in New Zealand, is complemented by this new scientific dimension. The new Greater Pleiades Complex becomes a crucial object of study for astronomers, seeking to trace the origins of other stars, including the possibility of identifying the Sun’s ancestral group.
The new method and the study of dispersion
The innovative technique based on stellar rotation made it possible to clearly distinguish stars with similar ages, even with considerable spatial distances between them. This precision is a breakthrough in astronomy, offering a new way to map and categorize scattered stellar associations. The study demonstrates the effectiveness of combining observations from different space missions to achieve unprecedented analytical depth.
- Acceleration in the dispersion of clusters
- New rotation technique as an age meter
- Thousands of new stars in the Greater Pleiades Complex
The role of the Gaia and TESS satellites
Data from Gaia, which monitors the position and movement of billions of stars, was essential for mapping the movement of candidate stars. In addition, TESS provided rotational speed measurements, which acted as the age filter. The synergy between the two missions resulted in the robust identification of previously unknown members of the cluster.
Cosmic families in transformation
The identification of the Greater Pleiades Complex as a disintegrating stellar association shows a natural process of galactic evolution. Over time, the gravitational influence of the Milky Way and other stars causes the members of a cluster to separate, transforming a dense group into a broader, more dispersed stellar association.