Friday 05 September 2025
Astronomers have made a significant discovery about the lives of certain stars, shedding light on their formation and evolution. Researchers have found that blue horizontal-branch (BHB) stars, which are old and metal-poor, exhibit a higher binary fraction than previously thought.
BHB stars are interesting because they’re relics from the early days of our galaxy’s formation. They’re formed when low-mass stars like our sun exhaust their fuel and expand to become red giants, before shedding their outer layers and shrinking back down to become white dwarfs. The blue horizontal-branch phase is a brief period where these stars briefly rekindle their youth and become hot and blue.
The study used data from the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST) to identify 299 BHB stars with multiple radial velocity measurements. By analyzing these velocities, researchers were able to determine which of these stars are likely to be part of a binary system.
The results show that about 31% of BHB stars have a companion star, which is higher than the estimated 18-20% binary fraction for similar stars in other studies. The research also found that halo-like BHB stars, which are thought to have formed early in the galaxy’s history, have a lower binary fraction than disk-like BHB stars.
The study suggests that these differences could be due to different formation pathways. Halo-like BHB stars may have formed through single-star evolution channels, while disk-like BHB stars may have resulted from binary interactions and mergers. This difference could also be related to the metallicity of the stars, with halo-like stars being more metal-poor.
The discovery has implications for our understanding of stellar evolution and the formation of the galaxy’s structure. It highlights the importance of studying binary systems in order to gain a better understanding of how stars form and evolve.
Furthermore, the study demonstrates the power of large-scale surveys like LAMOST, which can provide valuable insights into the properties of distant stars. By analyzing the radial velocity variations of these stars, researchers can identify potential binaries and gain a deeper understanding of their properties.
The research has also sparked further questions about the role of binary interactions in shaping the evolution of BHB stars. As scientists continue to study these stars, they may uncover new insights into the complex dance between star formation, stellar evolution, and galaxy structure.
Cite this article: “Blue Horizontal-Branch Stars Revealed to Have Higher Binary Fraction Than Previously Thought”, The Science Archive, 2025.
Stars, Binary, Blue Horizontal Branch, Lamost, Radial Velocity, Metal-Poor, Old Stars, Galaxy Formation, Evolution, Astronomy
