Texas Astronomer Solves Decades-Old Mystery About Aging Stars

New research led by Texas Astronomer Dr. Natalie Gosnell, is shedding light on a longstanding mystery about certain stars called “blue stragglers” – stars that appear bluer in color and hotter than they should be given their advanced age.

Gosnell, a W. J. McDonald Postdoctoral Fellow at the University of Texas, joined us to talk about her research.

She and her team recorded the first observations of one of astronomers’ main theories for how “blue stragglers” take on their perplexing appearance – a process called “mass transfer.”

With mass transfer, aging “red giant” stars with gaseous outer layers in a two-star system “spill” some of their gas onto a smaller companion star. The larger star is eventually left with only its core, making it a “white dwarf”, and the smaller star becomes heavier. The building up of mass in the smaller star makes it bluer, brighter and hotter than it was before – thus, a “blue straggler” is born.

An artist's rendering of the "mass transfer" process that forms a "blue straggler" - a normal star that has gained mass from its companion "red giant" star, and now appears "born again" - bluer, brighter and hotter than it was before. (NASA/ESA, A. Feild [STScI])

An artist’s rendering of the “mass transfer” process that forms a “blue straggler” – a normal star that has gained mass from its companion “red giant” star, and now appears “born again” – bluer, brighter and hotter than it was before. (NASA/ESA, A. Feild [STScI])

In a statement, Gosnell said her research has broader implications for studies on the evolution of stars.

(Natalie Gosnell)

(Natalie Gosnell)

“It’s the first time we can place limits on the fraction of blue stragglers formed through mass transfer,” she said.The study is the first observational proof astronomers have for any theory of how “blue stragglers” form, something Gosnell highlighted in our interview.

“Real scientific progress is made when you have interplay and a synergy between observations and theory,” she said. “And so here, for the first time, we really have the observational evidence that one of these theories is more important than the others, and so now we can go back and focus our theoretical efforts in that direction.”

Dr. Gosnell’s research is published in the current issue of The Astrophysics Journal. She plans to conduct follow-up research at the McDonald Observatory in West Texas.

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