Astronomers discover retired AGB star interloping through young star-forming region

A team of researchers from the University of Sheffield and Imperial College London have discovered an old, evolved star, called Asymptotic Giant Branch (AGB) interloping through a young star-forming region, challenging previous assumptions that these retired stars cannot encounter young stars and their planetary systems.

While young interloping stars have been spotted previously, this discovery marks the first time that the team has discovered a retired AGB star passing through the region.

"Until now, researchers have been sceptical that these old, evolved stars could ever meet young stars that are forming planets, so this discovery reveals much more about the dynamics, relationships and journeys of stars," says Dr Richard Parker, a lecturer in Astrophysics in Department of Physics and Astronomy at the University of Sheffield, and the lead author of the study.

Retired AGB stars are known to produce large quantities of radioactively unstable chemical elements, Aluminium-26 and Iron-60, which were delivered to our young Solar system at the epoch of planet formation. They are believed to have played a significant role in shaping our early Solar system and have likely contributed to the internal heating of Earth during its formative stages.

The presence of these chemical elements may have had far-reaching consequences for our planet, potentially influencing critical processes like plate tectonics, which have helped maintain a breathable atmosphere on Earth. Understanding the abundance of these elements in the early Solar system is crucial for unravelling the mysteries of our planet's history.

"Gaia is revolutionising our ideas about how stars form, and then subsequently move in the Galaxy. This discovery of an old, evolved star in close proximity to young planet-forming stars is a wonderful example of the power of serendipity in scientific research," said Dr Christina Schoettler, an Astrophysics research associate in the Department of Physics at Imperial College London, who identified the AGB star in the Gaia DR3 data.

The researchers now plan to search for other evolved stars in young star-forming regions to establish how common these retired interloping stars are.