Old and young at the same time? The mystery of red giants

At the end of their life, main sequence stars (which also include our Sun) develop into red giants. This fate is predestined for them. However, it’s not so easy to figure out the true age of a red giant. This is because there are many individual factors that can accelerate or slow down their development.

Astronomers have gotten rather good at this in recent years, but there are always exceptions. Four years ago, researchers of the Leibniz Institute for Astrophysics and the Max Planck Institute for Astronomy discovered red giants whose age estimates differed by up to four billion years depending on the estimation method. “The stars appeared to be old and young at the same time,” recalled Dr. Saskia Hekker from MPS and the University of Aarhus in Denmark, who was a member of both teams at the time. The researcher was never able to let go of the paradox, and now, with her colleague Dr. Jennifer A. Johnson of Ohio State University, they’ve solved it. The giant stars are only faking their youthful age.

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