The Pleiades star cluster, often referred to as the Seven Sisters for its most prominent seven stars visible to the naked eye, is much larger and more complex than previously thought. Astronomers using NASA’s TESS spacecraft and the European Space Agency’s Gaia have discovered around 20 times more stars within this iconic grouping, highlighting a deeper understanding of star formation and challenging long-held perceptions of this celestial landmark.
This significant discovery stems from a novel approach: analyzing the rotational speeds of known stars within the Pleiades region. Led by Andrew Boyle, a graduate student at UNC-Chapel Hill, the research team utilized data from Gaia and TESS to measure these rotations. Young stars spin faster than their older counterparts, acting as cosmic “clocks” for astronomers. By charting these spinning speeds, researchers can identify familial connections between stars that have drifted apart since their birth within the same nebula.
Uncovering a Hidden Stellar Family
This method unveiled thousands of previously undetected members of the Pleiades family scattered across a wider area than initially recognized. The finding fundamentally alters our understanding of this well-known cluster, revealing it as more of a sprawling stellar community rather than a tightly knit group of seven. Andrew Mann, professor of physics and astronomy at UNC-Chapel Hill and a member of the research team, explains, “We’re realizing that many stars near the sun are part of massive extended stellar families with complex structures.”
The implications extend beyond simply revising star counts.
A New Lens on Star Formation
This technique promises to reshape our understanding of star formation and galactic evolution. By tracing these rotational “family trees,” scientists can pinpoint the birthplaces of stars, gaining invaluable insights into how clusters like the Pleiades coalesced from giant molecular clouds. Moreover, this method might even help uncover the family origins of our own Sun, providing crucial clues about the formation of the solar system and the Milky Way galaxy itself.
“By measuring how stars spin, we can identify stellar groups too scattered to detect with traditional methods — opening a new window into the hidden architecture of our galaxy,” concludes Boyle.
The Pleiades cluster’s expanded size underscores the dynamic nature of star systems and the vastness of our galactic neighborhood. What was once thought of as a simple grouping of seven bright stars has become a testament to the intricate tapestry of stellar relationships woven throughout space.
