Ejected stars do not just wander off into space, suggest researchers

  • Researchers from the University of Sheffield found that ejected stars are able to interact with other star forming regions
  • Findings from the new study will help us to understand our planetary system in the context of others and determine whether there could be more planetary systems like our own

New research from the University of Sheffield has found that newly formed stars which are ejected from their birth region do not just wander off into space, but can interact with other star forming regions.

When stars like the Sun form they are born with tens to tens of thousands of stellar siblings. These stars interact with each other, which can have an impact on the young planetary systems forming around them.

Occasionally, these interactions cause stars to be ejected from their birth region altogether and it was thought that these stars simply wander off into space and do not encounter any other star forming regions.

The research, published in Monthly Notices of the Royal Astronomical Society Letters, analysed five stars that had been ejected from the regions where they were formed. Three of the stars have been ejected from the Orion Nebula Cluster (ONC) star forming region, one has been ejected from an unknown region but is heading towards the ONC and the last one has already interacted with and passed through most of the ONC.

All of these stars showed excess radiation emission in IR (infrared) or UV (ultraviolet) bands that are indicative of the presence of a protoplanetary disc, a disc of gas and dust surrounding a young star, which will form, or has already formed planets.

The ground breaking research is the first to investigate if there are ejected stars passing through a second star-forming region with a protoplanetary disc and whether this disc might survive the second encounter. This has only been made possible thanks to the exquisite precision of data from the Gaia space telescope, which enabled the researchers to accurately determine where these stars had been, and where they were heading to.

I knew from previous research that stars ejected from one star-forming region could become a visitor to another, but was surprised to find that their protoplanetary discs might be resilient enough to first survive the ejection and then the encounter with a second dense region.

Christina Schoettler

Lead author of the research from the University of Sheffield

Christina Schoettler, lead author of the research from the University of Sheffield, said: “I knew from previous research that stars ejected from one star-forming region could become a visitor to another, but was surprised to find that their protoplanetary discs might be resilient enough to first survive the ejection and then the encounter with a second dense region.

“Now that we know that stars can run away with their discs from their birth region and visit another region, we can search for them more specifically to find out how rare these occasions really are.”

Findings from the research will help us to understand our planetary system in the context of others and determine whether there could be more planetary systems like our own.

Dr Richard Parker, from the University of Sheffield’s Department of Physics and Astronomy, said: “The more we investigate the early stages of star and planet formation, the more surprises are thrown up. Despite the rather hostile environment some stars are born in, we are finding that their planetary systems can survive a multitude of destructive encounters with other stars.”

The University of Sheffield’s Department of Physics and Astronomy explores the fundamental laws of the universe and develops pioneering technologies with real-world applications. Researchers are looking beyond our planet to map out distant galaxies, tackling global challenges including energy security, and exploring the opportunities presented by quantum computing and 2D materials.

Research – full paper

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