Quiet black holes with a stellar companion raise questions about how they form

• Three quiet black holes with stellar companions have been discovered using the Gaia spacecraft. These black holes are not active and are only observed through their effects on nearby stars. The findings suggest that these systems formed from asymmetrical binary stars, where one star became a black hole while the other remained as a normal star.
• The study raises questions about how these systems formed, particularly regarding the survival of close-orbiting companions. The Roche-lobe overflow model is considered a possible explanation for how the material from the expanding star is captured by the companion star, allowing the original star to become a black hole without merging. The findings highlight the complexity of black hole formation and the need for further research.

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