Seven Sisters Pleiades Star Cluster Stuns Astronomers With A Hidden Secret
The shimmering Pleiades star cluster has just shed its millennia-old reputation as a collection of Seven Sisters. Thanks to new data gleaned from the TESS and Gaia star-tracking spacecrafts, astronomers have revealed that this iconic group is part of a diaspora up to 20 times larger than previously imagined. Published this week in The Astrophysical Journal, the findings introduces us to the Greater Pleiades Complex that could challenge and change our understanding of how star clusters like our own Milky Way take shape.
No doubt, the Seven Sisters have a deep part in human history, appearing in ancient texts from the Old Testament to the Talmud, and even lending its image to the logo of the Japanese automaker Subaru. (Fun fact: the latter shows only six stars because, for the most part, the seventh isn't visible to the naked eye.) Yet, Pleiades' true and sheer scale has remained hidden until now.
A team from the University of North Carolina at Chapel Hill, combined precision data from NASA’s Transiting Exoplanet Survey Satellite (TESS) and the European Space Agency's Gaia missions and were then able to measure the spin rate of the stars. Just as a pendulum slows down over time, young stars spin rapidly, gradually losing speed as they age.
The researchers realized they could use this rotational velocity as an accurate "cosmic clock" to identify distant stars that shared the exact same birth time and location. By cross-referencing these age fingerprints with Gaia's measurements of stellar position and movement, researchers successfully tracked down thousands of long-lost siblings that had drifted far from the primary cluster over millions of years.
Andrew Boyle, lead author and a graduate student in physics and astronomy commented that “this study changes how we see the Pleiades—not just seven bright stars, but thousands of long-lost siblings scattered across the whole sky.” It suggests that many seemingly isolated star groupings in our local neighborhood may, in fact, belong to massive, slowly dissolving associations, forming a complex, interwoven structure previously invisible to traditional observation methods.
Of course, this new technique has implications far beyond the Pleiades itself as it provides astronomers with a means to reconstruct the birth environments of stars, planets, and, by extension, planetary systems, including our own. It would be interesting to see how scientists use this technique to trace the origin of the Sun, perhaps uncovering hidden clues about the Milky Way’s past. As Andrew Mann, co-author and professor of physics and astronomy stresses, “Our work provides a new way to uncover these hidden relationships.”
