A gravitational wave rocket

[John Clark]

For the first time a sort of gravitational wave rocket has been found. By re-examining the data from the LIGO and Virgo gravitational wave observatories researchers report on January 6 they have detected the merger of 34 and 29 solar mass Black Holes that resulted in a Black Hole of about 62 solar masses with about one solar mass being converted into gravitational waves. What makes this merger unusual is that it was not symmetrical, the axis of spin of the 2 black holes were not aligned with each other and neither was aligned with the axis of orbit around each other. This would indicate that the 2 stars that form them (assuming these 2 large Black Holes were actually formed from the corpses of dead stars) were not born in an isolated system but probably came from a denser environment like a globular cluster. Even more interesting is that the misalignment of the spins means that the gravitational waves emitted were not emitted symmetrically, and gravitational waves carry some linear momentum. So the resulting 62 Solar mass Black Hole must've received a pretty substantial kick causing it to move pretty fast, and that's just what the researchers found, because of that kick the huge 62 solar mass Black Hole started moving at least 700 km a second and probably closer to 1500.  It's probably moving fast enough to escape whatever galaxy it was in.

Evidence of large recoil velocity from a black hole merger signal

John K Clark

[Brent Meeker]

Kudos to whomever did the calculation for this.  But I would have thought that most collisions would be misaligned in both spin axes and impact plane.  The Sun's spin axis isn't aligned with the Milky Way's axis of rotation, so I had assumed most stars have randomly directed spin axes.

Brent

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[John Clark]

On Thu, Jan 13, 2022 at 1:37 PM Brent Meeker <meeke...@gmail.com> wrote:

> Kudos to whomever did the calculation for this.  But I would have thought that most collisions would be misaligned in both spin axes and impact plane.  The Sun's spin axis isn't aligned with the Milky Way's axis of rotation, so I had assumed most stars have randomly directed spin axes.

Stars do have random axis of rotations in general but not if you're talking about double stars, and the sun is rather unusual in being only a single star, most stars are double stars, and they were created at the same time from the same rotating cloud of gas and dust and thus have similar axis of rotation, so when the resulting stars turned into Black Holes they would also have similar axes. And indeed most of the Black Hole mergers so far detected by gravitational waves have been of that sort, but not this one, that's what makes it so unusual. This system must've been formed by two stars that formed at different places at different times but then got close together and somehow went into orbit around each other.  

John K Clark    See what's on my new list at  Extropolis

qbj

[Lawrence Crowell]

It is possible for a binary star system to interact with a third star so there is an exchange.  We do normally expect binary star systems to have similarly oriented angular momenta.

 This is an interesting result. To compute this would have been tough. This is a case of a Robinson-Trautman twisting solution or a twisting type N. The addition of the two angular momenta results in the occurrence of angular momenta perpendicular to the initial angular momenta. This can be seen in with the classical group [L_i, L_j] = ε_{ijk}|L|^2 n_k, for n_k a unit vector. This means there is the emission of angular momentum in the gravitational radiation. The calculation was most likely done numerically.

LC