LIGO –Tracing the Origins of Colliding Black Holes

Binary Black Holes


“Researchers up until now have theorized the formation and existence for pairs of black holes in the universe, but the origins of their predecessors, stars, still remains a mystery,” said LIGO and Vanderbilt University astrophysicist, Karan Jani and co-author Avi Loeb at Harvard University about a new study that leveraged Einstein’s general theory of relativity, which tells us how black holes interact and eventually collide, using LIGO data to take an inventory of the universe’s time and space resources at any given point.

Jani and Loeb developed the constraints accounting for each step in the binary black hole process: the number of available stars in the universe, the process of each star transitioning to an individual black hole, and the detection of the eventual collision of those black holes—picked up hundreds of millions of years later by LIGO as gravitational waves emitted by the impact.

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Since the breakthrough in gravitational wave astronomy back in 2015, scientists have been able to detect more than a dozen pairs of binary black holes by their collisions into each other due to gravity. However, scientists still debate how many of these black holes are born from stars, and how they are able to get close enough for a collision within the lifetime of our universe.

The research, which appears in The Astrophysical Journal Letters, will help future scientists interpret the underlying population of stars and test the formation theories of all colliding black holes across cosmic history.

“With this study, we did a forensic study of colliding black holes using the astrophysical observations that are currently available,”said lead author, Jani. “In the process, we developed a fundamental constraint, or budget, which tells us about the fraction of stars since the beginning of the universe that are destined to collide as black holes.”

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“From the current observations, we find that 14 percent of all the massive stars in the universe are destined to collide as black holes. That’s remarkable efficiency on nature’s part,” concludes Jani. “These added constraints in our framework should help researchers trace the histories of black holes, answering old questions and undoubtedly opening up more exotic scenarios.”

Source: Karan Jani et al. Global Stellar Budget for LIGO Black Holes, The Astrophysical Journal (2020). DOI: 10.3847/2041-8213/ab6854

The Daily Galaxy, Spencer Turney via Vanderbilt University

Image at top of page: Aurore Simonnet illustration shows two merging black holes similar to those detected by LIGO. The black holes are spinning in a non-aligned fashion, which means they have different orientations relative to the overall orbital motion of the pair. LIGO found hints that at least one black hole in the system called GW170104 was non-aligned with its orbital motion before it merged with its partner. LIGO/Caltech/MIT/Sonoma State.

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