Cosmic Collisions:
Close Encounters in the Gum Nebula

When stars pass very close to each other, they potentially kick up comets from each other’s Oort clouds and cause heavy bombardment events. A collision of stellar associations can serve as a laboratory of close stellar encounters. A stellar association is a very loose cluster of stars that share a common origin, but have become gravitationally unbound. Dr. Alexandra Yep examines the collision of two stellar associations in the Gum Nebula in the southern sky, using multiple simulations. Fifty pairs of stars in these two associations are projected to pass close to each other. To ascertain how frequently association collisions occur, a linear survey is conducted on a total of 6 stellar associations in the plane of the Galaxy. Dr. Yep concludes that an association in this region may experience an association collision every 20 million years (20 Myr), and stars within that association may on average experience a close stellar encounter every 84 Myr due to association collisions.

Dr. Alexandra Yep is a poet turned astronomer. After earning her BFA in creative writing and classical studies, she dove straight into quantum mechanics on her way to a Ph.D. in astronomy. Now a professor at Agnes Scott College in Atlanta, Georgia, she researches young stars and star clusters. As part of her work, she discovered several star clusters in the Gum Nebula which are now known as Yep-1, Yep-2 and Yep-3 and is only the second woman to have earned this type of naming honor.

Dr. Yep quips, “I like stars (the love is quite simplistic… they look pretty, and Tolkien liked them), and collisions and interactions are exciting.”


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