Free Astronomy Magazine July-August 2024

38 JULY-AUGUST 2024 ASTRO PUBLISHING by NOIRLab − Josie Fenske Origin of differences in giant binary stars revealed I t is estimated that up to 85% of stars exist in binary star systems, some even in systems with three or more stars. These stellar pairs are born together out of the same mo- lecular cloud from a shared abun- dance of chemical building blocks, so astronomers would expect to find that they have nearly identical com- positions and planetary systems. However, for many binaries that isn’t the case. While some proposed explanations attribute these dissim- ilarities to events occurring after the stars evolved, a team of astronomers have confirmed for the first time that they can actually originate from before the stars even began to form. T his artist’s impression illustrates a binary pair of giant stars. Despite being born from the same molecular cloud, as- tronomers often detect differences in binary stars’ chemical compositions and planetary systems. One star in this system is shown to host three small, rocky planets, while the other star hosts two gas giants. Using Gemini South’s GHOST, a team of astronomers have confirmed for the first time that these differences can be traced back to inhomogeneities in the primor- dial molecular cloud from which the stars were born. [NOIRLab/NSF/AURA/J. da Silva (Spaceengine)/M. Zamani]