Leveraging Einstein’s General Theory of Relativity, Astrophysicists Calculate How Many Stars Will Eventually Collide as Black Holes

Two Merging Black Holes

Artist’s conception shows the collisions of two black holes similar to those detected by LIGO and Virgo gravitational-wave detectors. Credit: LIGO/Caltech/MIT/Sonoma State (Aurore Simonnet)

Since the breakthrough in gravitational wave astronomy back in 2015, scientists have been able to detect more than a dozen pairs of closely located black holes—known as 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.

Now, a promising new study developed by one Vanderbilt astrophysicist may give us a method for finding the number of available stars in the history of the universe that collide as binary black holes. 

The research, which was published in The Astrophysical Journal Letters on January 31, 2020, will help future scientists interpret the underlying population of stars and test the formation theories of all colliding black holes across cosmic history.

“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 Vanderbilt astrophysicist and lead author of the study Karan Jani. “With this study, we did a forensic study of colliding black holes using the astrophysical observations that are currently available. 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.”

Leveraging Einstein’s general theory of relativity, which tells us how black holes interact and eventually collide, Jani and co-author Abraham Loeb at Harvard University used LIGO events on record to take an inventory of the universe’s time and space resources at any given point. They then 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.

“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,” added 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.”

Reference: “Global Stellar Budget for LIGO Black Holes” by Karan Jani and Abraham Loeb, 31 January 2020, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ab6854

The research is funded by the GRAVITY program at Vanderbilt, and supported in part by the Black Hole Initiative at Harvard University, which is funded by grants from the John Templeton Foundation and the Gordon and Betty Moore Foundation.

6 Comments on "Leveraging Einstein’s General Theory of Relativity, Astrophysicists Calculate How Many Stars Will Eventually Collide as Black Holes"

  1. David J Franks | February 10, 2020 at 3:45 pm | Reply

    When all the stars in all the galaxies die-off, does anyone know whether they’ll all get sucked into the centre and become one massive black hole or will the Galaxy disperse leaving all the dead stars and black holes to go their own way? Or will it just carry on spinning indefinitely with the Black Holes and dead stars in it?

    ‘Steady state of the infinite’ theory
    Infinite space infinite universes no beginning no end.

  2. So just like how binary black holes collide, could two quasars collide??

    • David J Franks | February 10, 2020 at 6:38 pm | Reply

      Since quasars have a Galaxy of their own, and given that galaxies are flying apart with the expansion of the universe, then in my opinion, I don’t think they would collide. But if the galaxies are part of a cluster of galaxies then maybe those galaxies might collapse in on each other and then collide.

      ‘Steady state of the infinite’ theory
      Infinite space infinite universes no beginning no end.

      • David J Franks | February 10, 2020 at 6:49 pm | Reply

        Second thoughts, according to physics.org. Colliding galaxies are quite common. So the answer to your question would be now, probably yes they could collide one day. It would be a hell of a bang!


    All of them, Katie!

  4. SRT is completely erroneous since it is based on the wrong kind of transformations: they have lost the scale factor characterizing the Doppler effect. First, Lorentz considered a more general form of transformations (with a scale factor), but then he, and also Poincare and Einstein equated it 1 without proper grounds. Their form was artificially narrowed, the formulas became incorrect. This led to a logical contradiction of the theory, to unsolvable paradoxes. Accordingly, GRT is also incorrect.
    For more details, see my brochure “Memoir on the Theory of Relativity and Unified Field Theory” (2000):

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