Secret origins of young star clusters traced to three families

An international team of astronomers has uncovered the formation history of young star clusters, many of which are visible to the naked eye at night.

This remarkable research reveals that most nearby young star clusters belong to only three families, each originating from very massive star-forming regions.

The findings offer new insights into the effects of supernovae on the formation of giant gas structures in galaxies like our Milky Way.

Young star clusters

Young star clusters have formed relatively recently in the cosmic timeline, typically within the last few hundred million years.

These groups of stars often emerge from large clouds of gas and dust, known as molecular clouds, where new stars are born. They are crucial for astronomers studying stellar evolution, as they provide snapshots of the early stages of star development.

There are two main types of young star clusters: open clusters and globular clusters. Open star clusters, which formed more recently, contain a few hundred to a few thousand stars that are loosely bound by gravity and can disperse over time.

“Found in irregular galaxies and spiral galaxies like the Milky Way, open clusters contain both old and young stars and are generally much younger than globular clusters – typically they are less than a billion years old,” noted NASA.

Star clusters can vary in size and brightness, and their stars often range from very massive and hot to smaller, cooler ones. Studying these stellar groups helps scientists understand the processes of star formation and the dynamics of stellar populations in galaxies.

Ancestry of young star clusters

The research team was led by Cameren Swiggum and João Alves from the University of Vienna, along with Robert Benjamin from the University of Wisconsin-Whitewater.

Using precise data from the European Space Agency’s (ESA) Gaia mission and spectroscopic observations, the researchers traced the origins of 155 young star clusters within a radius of about 3,500 light-years around the Sun.

Their analysis shows that these star clusters can be divided into three families, named after the most prominent clusters within them: Collinder 135 (Cr135), Messier 6 (M6), and Alpha Persei (αPer).

“Young star clusters are excellent for exploring the history and structure of the Milky Way. By studying their movements in the past and thus their origin, we also gain important insights into the formation and evolution of our galaxy,” noted Alves.

The team’s findings suggest that these star clusters originate from only three very active and massive star-forming regions.

Interconnectedness of star clusters

“These findings offer a clearer understanding of how young star clusters in our galactic neighborhood are interconnected, much like members of a family or ‘bloodlines’,” said Swiggum, lead author of the study.

By examining the 3D movements and past positions of these star clusters, the team identified their common origins and located the regions in our galaxy where the first stars in these respective star clusters formed up to 40 million years ago.

The study revealed that over 200 supernova explosions must have occurred within these three star cluster families, releasing enormous amounts of energy into their surroundings. The volatile energy likely had a significant impact on the gas distribution in the local Milky Way.

“This could explain the formation of a superbubble, a giant bubble of gas and dust with a diameter of 3,000 light-years around the Cr135 family,” explained Swiggum.

Our solar system is also embedded in such a bubble, known as the Local Bubble, which is filled with very thin and hot gas.

“The Local Bubble is probably also linked to the history of one of the three star cluster families,” noted Swiggum. “And it has likely left traces on Earth, as suggested by measurements of iron isotopes (60Fe) in the Earth’s crust.”

A galactic time machine

“We can practically turn the sky into a time machine that allows us to trace the history of our home galaxy,” said Alves. “By deciphering the genealogy of star clusters, we also learn more about our own galactic ancestry.”

In the future, the experts plan to investigate more precisely whether and how our solar system has interacted with interstellar matter in our home galaxy, the Milky Way.

This research not only advances our understanding of star formation but also provides a deeper insight into the complex history of our galaxy.

The findings underscore the interconnectedness of stellar phenomena and their lasting impact on the structure of the Milky Way.

The study is published in the journal Nature.

Image Credit: ESO/STScI Digitized Sky Survey II

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