New simulations suggest the Milky Way is home to around 170 million stellar-mass black holes that have remained largely undetectable because they emit no light. Black holes formed from the collapse of massive stars are among the most difficult objects to detect. That has made it difficult for astronomers to estimate how many stellar-mass black holes exist within the Milky Way. Spread over the Milky Way’s 13.6-billion-year history, the formation of 170 million stellar-mass black holes corresponds to an average of roughly one new black hole every 80 years. Model Variations and Black Hole Mass Outcomes ©arXivThe researchers conclude that future surveys could measure not only the number of stellar-mass black holes in the Milky Way but also their masses and motions.