A mysterious pair of sun-like stars reveals secrets of stellar evolution and magnetic cycles

Star system: HD 81809 A | Distance from the Sun: 101 light years

Scientists have conducted a detailed study of HD 81809, a nearby binary system consisting of two stars very similar to our Sun. By using data from the TESS space telescope and ground-based spectroscopy, researchers discovered that these two stars have surprisingly different chemical compositions despite being born together. 

The primary star is a subgiant that is older and metal-poor, while the secondary star appears to have a composition similar to our Sun, likely due to recently absorbing material from its surroundings. Both stars exhibit 'sun-quakes' or oscillations, which allowed astronomers to determine that the system is about 10 billion years old—roughly twice the age of our Solar System. This discovery provides a unique look at how magnetic activity and chemical makeup change as stars like our Sun reach the later stages of their lives.

Scientific study

On the contradictory case of the binary system HD 81809 hosting two pulsating solar-like stars observed by TESS (external link)