At first glance, the Orion Nebula Cluster, the Pleiades, and the Hyades appear to be separate star groups, scattered across different parts of the night sky. Their distinct locations and appearances make it easy to assume they have no connection to one another.
However, new research suggests that these well-known star clusters might be more than neighbors – they might be snapshots of the same system, seen at different stages in life.
This surprising connection comes from scientists at the Institute for Advanced Studies in Basic Sciences (IASBS) in Iran and the University of Bonn in Germany.
The study shows that the Orion Nebula Cluster, the Pleiades, and the Hyades likely formed from the same original star system. The findings are changing how we think about star formation.
Star clusters at different life stages
The Orion Nebula Cluster (ONC) is the youngest of the trio – just 2.5 million years old. It’s also the most active, filled with thousands of young stars and surrounded by the gas cloud that birthed them.
You can spot it in Orion’s Sword, although it looks like just one bright “star” to the naked eye.
Then there’s the Pleiades – visible as a tight knot of stars nearby in the sky. At 100 million years old, its stars are more spread out, having had time to drift away from each other.
Finally, the Hyades is around 700 million years old. Its stars are far more scattered and fewer in number.
Snapshots of an evolving star system
Despite their different ages and distances, scientists believe these three clusters are linked.
“Our highly precise stellar dynamics calculations have now shown that all three star clusters originated from the same predecessor,” said study co-author Dr. Pavel Kroupa.
“The Orion Nebula, Pleiades and Hyades are like three different photos of the same person. These three photos show this entity at different ages: as a baby, adolescent and elderly.”
Star clusters follow a growth pattern
This discovery isn’t just poetic – it’s pointing to something deeper about how stars form. According to the researchers, open star clusters might follow a consistent pattern in their development, regardless of the specific molecular cloud that births them.
“It is a bit like if the same person was being born over and over again,” said Dr. Kroupa. “From this we can learn that open star clusters seem to have a preferred mode of star formation.”
“It appears that there is a preferred physical environment in which stars form when they evolve within these clouds.”
To test this idea, Dr. Ghasem Safaei and his team at the IASBS used powerful computer simulations.
The experts modeled how a dense, young cluster like Orion could naturally transform into the more spread-out Pleiades, and then into the elderly Hyades, over hundreds of millions of years.
Millions of years of star life
The simulations were based on careful calculations of how the stars interact with each other and with their environment. Over time, a cluster loses stars and gas due to gravitational forces, both internal and external.
“This research shows that it is entirely plausible that star clusters such as the Orion Nebula Cluster follow a development path that transforms them into systems like Pleiades and later on Hyades,” said study co-author Professor Hosein Haghi.
The models ran for 800 million years and started with the latest real-world data – high star density, compact shapes, and a high number of double stars.
“The results show that clusters such as the Orion Nebula Cluster can lose up to 85 percent of their stars but nevertheless retain a coherent structure similar to Hyades, after they have passed through an intermediate stage similar to Pleiades,” said Dr. Safaei.
Star clusters with a common origin
What makes this even more intriguing is the fact that all three clusters sit in roughly the same region of the night sky. For decades, astronomers have wondered if this is just a coincidence or something more.
The team believes this alignment supports the idea that they share a common origin. It could reflect how these clusters form and evolve in the same part of our galaxy, influenced by similar conditions.
A stellar story in motion
Understanding these connections also helps astronomers grasp how internal and external forces shape a star cluster’s fate.
“This research gives us a deeper understanding of how star clusters form and develop and illustrates the delicate balance between internal dynamics and external forces such as the gravitational pull of the Milky Way,” said study co-author Professor Akram Hasani Zonoozi.
The research doesn’t just reveal how one star cluster ages. It shows how theory and observation can work hand-in-hand to reconstruct a cosmic story billions of years in the making.
As researchers refine these models, they may unlock similar patterns in other parts of the Milky Way – and perhaps even beyond.
The full study was published in the journal Monthly Notices of the Royal Astronomical Society.
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