by ESO

Observations made with ESO’s Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein’s theory of general relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton’s theory of gravity. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole. This artist’s impression illustrates the precession of the star’s orbit, with the effect exaggerated for easier visualisation. Credit: ESO/L. Calçada

Observations made with ESO’s Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein’s general theory of relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton’s theory of gravity. This long-sought-after result was made possible by increasingly precise measurements over nearly 30 years, which have enabled scientists to unlock the mysteries of the behemoth lurking at the heart of our galaxy.

“Einstein’s General Relativity predicts that bound orbits of one object around another are not closed, as in Newtonian Gravity, but precess forwards in the plane of motion. This famous effect—first seen in the orbit of the planet Mercury around the Sun—was the first evidence in favour of General Relativity. One hundred years later we have now detected the same effect in the motion of a star orbiting the compact radio source Sagittarius A* at the centre of the Milky Way. This observational breakthrough strengthens the evidence that Sagittarius A* must be a supermassive black hole of 4 million times the mass of the Sun,” says Reinhard Genzel, Director at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany and the architect of the 30-year-long programme that led to this result.

Located 26 000 light-years from the Sun, Sagittarius A* and the dense cluster of stars around it provide a unique laboratory for testing physics in an otherwise unexplored and extreme regime of gravity. One of these stars, S2, sweeps in towards the supermassive black hole to a closest distance less than 20 billion kilometres (one hundred and twenty times the distance between the Sun and Earth), making it one of the closest stars ever found in orbit around the massive giant. At its closest approach to the black hole, S2 is hurtling through space at almost three percent of the speed of light, completing an orbit once every 16 years. “After following the star in its orbit for over two and a half decades, our exquisite measurements robustly detect S2’s Schwarzschild precession in its path around Sagittarius A*,” says Stefan Gillessen of the MPE, who led the analysis of the measurements published today in the journal *Astronomy & Astrophysics*.

Most stars and planets have a non-circular orbit and therefore move closer to and further away from the object they are rotating around. S2’s orbit precesses, meaning that the location of its closest point to the supermassive black hole changes with each turn, such that the next orbit is rotated with regard to the previous one, creating a rosette shape. General Relativity provides a precise prediction of how much its orbit changes and the latest measurements from this research exactly match the theory. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole.

The study with ESO’s VLT also helps scientists learn more about the vicinity of the supermassive black hole at the centre of our galaxy. “Because the S2 measurements follow General Relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present around Sagittarius A*. This is of great interest for understanding the formation and evolution of supermassive black holes,” say Guy Perrin and Karine Perraut, the French lead scientists of the project.

This result is the culmination of 27 years of observations of the S2 star using, for the best part of this time, a fleet of instruments at ESO’s VLT, located in the Atacama Desert in Chile. The number of data points marking the star’s position and velocity attests to the thoroughness and accuracy of the new research: the team made over 330 measurements in total, using the GRAVITY, SINFONI and NACO instruments. Because S2 takes years to orbit the supermassive black hole, it was crucial to follow the star for close to three decades, to unravel the intricacies of its orbital movement.

A cosmic scale ‘Spirograph”, an Einsteinian play toy for the children of the Gods… Marvelous!

Not at all what I pictured when they said “dance”.

Typical stupid language they have to adopt when talking down to hoi polloi .

It was Kepler whose work described eliptical orbits not Newton. But you would not expect any one in astronomy to know stuff like that.

So are we talking about orbit or rotation ?

Hang on. As every student of media studies knows, you must NEVER use the same word twice. So you go to the thesaurus and grab the nearest work with a similar meaning and change what you were told by the expert source you are reporting. After all writing style is much more important than accurately reporting the science.

Relying on Tycho’s observations, Kepler found that Mars’ orbit described an ellipse. Newton applied universal gravitation to explain elliptical orbits, so the wording isn’t wrong.

Apogee… or Perigee?

Are you far or near to me?

Mutual attraction of gravity

Defines our stately ellipses.

Round and round and round we go,

Waltzing through the cosmos!

Gravitic duo dancing without cessation,

Provided there’s no external perturbation!

“a rosette”

That’s the pattern described by the observation.

No, not gravity, as an ellipse, more like a rose-shaped decoration, typically made of ribbon, a design, arrangement, or growth resembling a rose.

This description is closer to what have been observed & measured in laboratory experiments with electromagnetic plasma where a diocotron instability is created : “A diocotron instability is a plasma instability created by two sheets of charge slipping past each other. Energy is dissipated in the form of two surface waves propagating in opposite directions, with one flowing over the other.” (Wikipedia)

So-called “black holes” are mathematical myths: where tales are told of “near infinite density & in a near infinitely small space… a point (which has no space in mathematical terms).

That’s the base definition of a “black hole”.

But “near infinite” can’t be quantified.

As for Einstein’s thought experiment of relativity: gross that the authors of this article would suggest such rubbish.

Interesting James.

I read about diocotron instability here, but find that S2 is doing a much more beautiful job 🙂

I don’t see how this is in anyway related to diocotron instability or how this is better than the explanation offered in this case, as you claim.

Please explain.

Greg, take a look at what a diocotron instability looks like, seems to have more than a passing resemblance to the ‘rosette’ described in the article.

A diocotron instability spins around a center axis, much like what the article claims for the described phenomenon.

Agree 100%. The cosmos physicists won’t give up their addiction to Einstein and black hole myths. It is interesting that black hole theory wasn’t part of Einstein’s fantasies. Einstein claimed that they couldn’t exist. They were invented by David Finklestein in 1958. Cosmologists since then have tried to claim they are a natural byproduct of Einsteinian relativity.

Black holes are what you get when you apply linear equations to gravity and let distances tend towards zero.

String theory actually is an attempt to stop distances ever being zero.

Einstein’s equations are just another mathematical model and no doubt will be replaced with an even more precise one at some stage but for now they are remarkably accurate and useful.

To argue over their truth content is to betray a complete ignorance of the basis of science: Science does not uncover Facts or Truth, it creates efficient models that

work.IIRC Einstein said the singularities were mathematical curiosities.

It seems obvious that at some point before you get to silly infinite terms you need a different, probably more complex model since things will behave differently.

For the same reason I have no interest in what someone claims he thinks happened one billionth of a second after the big bang.

Wow… You obviously don’t know what Relativity is, and yet you dismiss it.

First, Relativity is indifferent about the source of acceleration, only that there is an acceleration. From there, the equations detail the curvature of space and time from that acceleration.

Second, the relationship between Relativity and gravity is that gravity is treated as an acceleration, not a force, inasmuch as one does not experience an external pushing or pulling while in freefall.

Also, a sufficiently strong electric field would produce similar results with charged objects, but would fail to do much to neutrally charged ones.

Einstein: a fraud & plagiarist.

– Exposing the Real Albert Einstein: https://principia-scientific.org/exposing-the-real-albert-einstein

– The Great Einstein Hoax: https://www.amazon.com/Great-Einstein-Hoax-Herb-Rose/dp/1478748095

– Albert Einstein was a Fraud: http://coconutrevival.com/?p=5656

– Einstein, plagiarist of the century: https://www.bibliotecapleyades.net/esp_einstein.htm

and:

https://www.bitchute.com/video/efWhgxlziT40/

Your third went a was poofed.

https://web.archive.org/web/20190522143640/http://coconutrevival.com/?p=5656

I don’t know how it is for black holes but treating something like it is infinitely large or infinitely small can make your arithmetic simpler with no practical difference in accuracy.

Example 1 – Calculate the gain of a simple feedback amplifier. Treat the gain of the operational amplifier as infinite. The gain will be the ratio of two resistors. Given component tolerances, it’s pointless to do the long form calculation using the actual gain of the operational amplifier.

Example 2 – Antennas. If you’re far enough from an antenna, you can treat it as a point source. You can calculate the signal using just the inverse square law. Your accuracy won’t improve if you use the long form calculation and your chances of making an error will go up a lot.

So, if somebody talks about ‘near infinite’ it does not immediately raise my hackles.

Bob, that’s a fug factor,

Because there are so many physical relationships, which aren’t known, but are assumed, that mathematical assumptions of relationships can only be taken with reasonable skepticism.

That of course is engraved at the heart of science.

Knowledge is the assumption of entities that are in essence imaginary and yet which correlate to our experience. The physical world of space and time is a handy

ideathat allows you to get in your car and drive to the nearest McDonald’s with remarkable reliability.Science merely puts numbers – accurate numbers – into that notion, so you know how long you will have to wait before you get there.

Scientists with third rate Brains will tell you that this is ‘strong evidence’ that the collection of consensus models we call the Real World™ actually exists in the way we conceive it. Philosophers have spent centuries trying to prove that it is, or indeed that it is not. Wittgenstein shrugged his shoulders and declared it unanswerable and Popper did something more useful, showed that it didn’t have to be true, to be

useful. Useful for predicting the way phenomena evolve.And as far back as Occam philosophers shrugged their shoulders and said ‘since when it comes to picking what models to use, the true one is never revealed, only the false ones (ones that don’t work), just pick an easy one, why not’?

Einstein didn’t do badly in mapping a complex set of observations onto the worldview of a two legged ape with a language designed merely to tell another ape where the best banana tree was…

But the only Truth and Certainty is to be found in religion, which avoids all this messy burden of proof by simply declaring itself to be True. So There.

Leo- did a burning bush tell you all that?

commieBob

April 17, 2020 at 12:52 am

like it is infinitely large or infinitely small can make your arithmetic simpler with no practical difference in accuracy.

—————————

Matter-Space-Time.

From my understanding, the problem with the black holes is not simply infinity as a concept, either in mass or space.

As per the main basic pillars of Newtonian physics, for as long as the most sensitive “effecting” factor,

the motion, one of three pillars of mass-distance-motion, can be mathematically applied, one can mathematically or otherwise address infinity.

While contemplating zero or infinity for gravity, aka mass and space, you still need motion or speed to be ~constant… where the clause of zero motion or infinite motion (speed) does not exist in reality or the possibility of observation… where the concept of either of

zero time (no time, non existence of the observer) or

infinite time (non existence in observation)

does not cut it.

Ignoring Newton leads to silly pompous claims like:

————

“Observations made with ESO’s Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way

————

Where the “observation” which consist with a condition not observed or observable,

forwarded only just for the sake of implying the validity of it by mentioning Einstein.

Wondering how they observe the supermassive non observed black hole at the centre of the

Milky Way!!!

Two wrongs doth not make it right.

It is actually worse with Einstein, and his famous equation where the constant speed of light happens to be the main factor.

Any model that ends up effecting the constancy of speed of light, the light motion, for whatever reason, is wrong.

cheers

The assumption is not of infinity but of a quantity sufficiently large that its reciprocal is negligibly small in comparison to the uncertainty is the other terms ( component values ).

Nothing infinite or infinitesimal there either. Similarly, the terms of the more rigorous calculation are deemed negligible, infinitesimal. At what distance they become negligible depends upon the accuracy required.

Most antennae have a 3D polar intensity map. Unlike a point source.

You probably chose poor examples.

oops, “negligible, NOT infinitesimal.” Not the same thing.

How about that integrating (Newtonian) gravitational attraction over a sphere produces the same result as treating the whole mass as a point at the center?

https://www.rockyhigh66.org/captions/Einstein.jpg

The ESO team of Prof Genzel provide a good precedent for how to study earth’s climate: wait a few decades till you have enough data to make meaningful observations-conclusions.

Does the Earth’s slightly elliptical orbit also precess around the sun?

Yes, it does

The precession of Mercury’s orbit is mostly explained by the influence of other bodies in the solar system. This was calculated to be 532 arc seconds per (Earth) century, using Newtonian theory, and the relativistic calculation added another 43, which agreed with the observed precession.

Earth’s orbit, and those of the other planets, are also subject to precession, but in those cases, the relativistic calculations are much smaller, compared with the Newtonian calculation, because of the decreased gravitational field of the sun.

Or not, as the case may be.

No actual image of a “black hole” or “accretion disk with event horizon” from this “study”…

could be as accurate as the claims of a black hole at the center of our galaxy when *that* news was from looking 30° in the wrong direction…

nobody talks about that…

So far this is a rosette with only one petal.

This did not “prove” anything, it only rejected the null hypothesis that Einstein was wrong with an excellent significance. Perhaps that would have been lost on the audience, but it is bad science to say that.

Good comment. I was going to say something similar but saw yours scrolling down.

As Feynman liked to point out, experiments never prove a theory right, they can only demonstrate that it is not wrong to the level of accuracy of the experiment and theory. So far Einstein has a pretty good batting average, but prediction is hard, especially about the future.

Feynman of course was talking about real science (particularly physics). As everyone knows, an experiment (or observation) can never prove AGW wrong, only demonstrate another way to argue that it must be right.

It’s kind of like arguing with Moon landing hoax believers, then.

So, they haven’t yet measured it over two orbits and it is doing exactly as Einstein proved in the early 1900s when he calculated the motion of mercury.

So nothing new then.

More funding please

Artists animation? So no real observation?

Amazing that most here poo-poo black holes. For me, this is powerful evidence of an undeniable reality.

To my mind it all gets even worse – when they speculate the existence of a super massive ANYTHING at the centre of the galaxy

The galaxy is patently being pictured as a large version of a solar system

But the Solar System is held together by an object (sun) that is many *many* times more massive than the combined mass of everything orbiting it

Yet seemingly, an object of 4 million sun-mass can hold together a system (the galaxy) containing 100 billion suns.

And a lot of them are multiple masses of El Sol

Its simply crazy. For the galaxy to behave like a solar system, it would need a central object with a mass of many multiples of the combined mass of everything orbiting it

So surely, the galaxy or more like a hurricane or even just the water going down the plughole in your bathtub.

There Is Nothing At Its Centre

Any object at the centre would need to be PERFECTLY symmetrical AND the ‘material’ surrounding it (100 billion stars plus dust & gas) must be perfectly symmetrically arranged.

If not, the object at the centre would be promptly yanked right out of there and into the swirling mass surrounding it – the Eye-Wall if you like

There can be nothing but “The Calm Of The Storm” at the centre of the galaxy. Surely.

What am I missing here…………….

I suspect you are talking about some of which you have very little knowledge. Just an impression.

One of the many key points you apparently misunderstand is that there is gravitational attraction in both directions.

The encircling galaxy is not held in thrall. All of those billions of stars are in partnership.

As will be Andromeda and other galaxies as they rush to join in the fun.

S2 is orbiting around “something” and since its gravity is controlling a star, it has to be pretty “massive”. And since it doesn’t show on any of our sensors, let’s just call it “black”.

Not only that, but the fact that it is making rosettes around the invisible object and not falling into it is proof that there is an event horizon inside its orbit.

The evidence supporting supermassive black holes at galactic centers is overwhelming. For example, from last year:

First M87 Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole

https://arxiv.org/abs/1906.11238

Wish I could post pictures.

“S2 is orbiting around “something” and since its gravity is controlling a star, it has to be pretty “massive”.

Yes, there is something massive there at the center of our galaxy. Nobody denies that, do they?

Star precessing around the rotating black hole is caused by relativistic frame-dragging of the space-time fabric. Mercury’s orbit precesses around the sun for the same reason (at a far lower rate).

As a pure layman, there are some skeptical questions I would raise about this.

Is this an unusual star that has an orbit around the galactic center that is far from being in the average orbital plane of the other stars in our galaxy? I understand that our sun orbits the center in such a way that we move a little above and below the average plane, and I suppose that would be true for most stars in the galaxy, but I gather it’s a small variation, otherwise we wouldn’t have the theory that the Milky Way is a spiral galaxy.

Unless this particular star is an oddball that orbits the compact radio source Sag A nearly perpendicular to the galactic plane and also roughly perpendicular to the line of sight to earth, we would not see an elliptical shaped orbit. From the perspective of a telescope array in Chile, it must appear to move back and forth virtually along a line and may not be visible to us for a lot of the orbit. If I understand correctly, we have observations for two full revolutions. The precession is not as great as is shown in the artist’s rendering. Are they really able to detect the position change of the star’s perigee accurately enough to make their claim?

Next question would be, isn’t the expected precession dependent on knowing the accurate masses of the two bodies? How do they calculate that? There isn’t even definite proof that the “compact radio source” Sagittarius A is a black hole. (Or that there are black holes for that matter).

And one more question. Is it believable that a star is moving at 0.03c? Could it be that the orbital path has been overestimated? Much like a helicopter estimating a car’s speed based on how long it takes to move between to points, if the two points are half a mile apart but are misjudged by the observer to be a mile apart, the driver who seems to be breaking the speed limit at 120mph, is really only going 60mph.

Well if they really can address those points (not saying that they can’t), then it is a replication study that replicates the work that showed relativistic effects on the orbit of Mercury. (That failed to refute Einstein).

It’s not from EurekAlert! so there’s a chance it’s not junk science.

The usual suspects are always claiming things about black holes that aren’t true. Say you want to derive the equation for escape velocity. Newton’s force law is:

,

Where is the force exerted on mass from mass , is Newton’s gravitational constant, and are the two masses, and is the distance between the two masses.

Newton’s second law of motion is . Substituting, we get

or .

The second mass cancels, so we can drop the subscript on the remaining mass. This is the acceleration formula for a single point mass (or a sphere that can be treated like a point mass).

Now we need to integrate this equation. Escape velocity, , appears at the surface of mass, , and drops to zero at infinite distance (definition of an escape velocity). We integrate from to . Therefore, we now have

.

The term on the right is straightforward, but the term on the left needs some work. We know that acceleration is defined as , or acceleration is the rate of change of velocity with respect to time. Substituting, we now have

.

The term , or the rate of change of distance with respect to time is a velocity. Substituting, we now have,

.

And finally we must change the limits to match the change in variable. At , ; and at , (again, the definition of an escape velocity). Therefore, we have

.

Integrating

,

and evaluating

.

Solving for we have

.

This is the standard Newtonian formula for escape velocity from the surface of a sphere. The mass must be inside a sphere of radius .

The escape velocity at an event horizon is the speed-of-light. If we set and solve for , we get

.

This is the standard formula for the Schwarzschild radius. It also has nothing to do with Einstein’s General Theory of Relativity (all calculations were pure Newtonian). When people say that Newton’s force law doesn’t predict black holes, they obviously don’t know what they are talking about.

Jim

Right you are.

Objects whose gravitational fields are too strong for light to escape were first hypothesized in the 18th century by John Michell and Pierre-Simon Laplace.

If it were understood that’ light speed or greater escape speed was the definition of a black hole in the Newtonian sense of escape speed (or of escape velocity magnitude) then things would be easier, I suppose. One issue is that, in basic relativity theory, or as in Special Relativity, “light speed” is in some ways a lot what you might think of for an *infinite* speed. For one thing, the vacuum light speed sets a kinetic limit on accelerating objects (as seen by a given observer), so particle accelerators can’t move a particle directly up to, or beyond the speed of light, say. Momentum-wise, you might as well be trying to get a particle up to an *infinite* Newtonian speed, as try to get it up to the speed of light in a real world accelerator! Another way of saying this is to relate regular space measurements to an alternate way of defining time, as it would tend to be measured “on the particle”. In those terms, the vacuum light speed comes out as infinite “proper speed”.

Now, just thinking of speed in *that* way, doesn’t the usual definition of a black hole event horizon as a sort of ‘ultimate barrier’ start to sound either just counter intuitive, or maybe even logically outrageous? We assume the gravitational field is so intense that even an infinite proper speed or an infinite build up of momentum couldn’t get through? This in itself might be enough to make someone think that the usual Einstein derived ideas about this must be wrong, that maybe some alternative version of General Relativity could start to make more sense, etc.

Then, of course, there has been a lot of speculation about what rotating black holes are capable of doing “up close’ — causality breaking time travel, anyone? Also, what in world does it mean when some physicists suggest that a black hole’s spherical event horizon must necessarily be “clothing” a hidden ‘singularity’? That singularity’s such a mythical beast that good physicists must never, ever see it? If the black hole is rotating fast enough, do we ever get to Peeping Tom this thing?

Suppose there really are tachyons, and suppose their timing characteristics are locked into a universal system of things? With no causal problems there, they’d be useful for sending signals around perhaps? Now I am starting to think of SF writer Fred Pohl’s classic Heechee novels, with clever aliens hiding out in the biggest black holes, and no problems communicating with outside agents at all (using special tachyonic gadgets).

Not only do Black Holes raise as many issues as they solve, I can’t help but think someone is eventually going to come face to face with one of those monstrous Singular points, if those are really possible?

Or, maybe none of the details on this are right at all, and black hole evidence is just evidence of some sort of ultra condensed star. Maybe you don’t even need tachyons for looking directly into these things, maybe slippery little photons get through no problem..

“Normal” black holes are indeed condensed stars. A neutron star is the collapsed core of a giant star which (before collapse) was between 10 and 29 solar masses. Larger than that, it becomes a black hole.

>>

David Blenkinsop

April 18, 2020 at 10:21 am

If it were understood that’ light speed or greater escape speed was the definition of a black hole in the Newtonian sense of escape speed (or of escape velocity magnitude) then things would be easier, I suppose.

<<

You mean there’s another definition of a black hole? What definition would that be?

>>

One issue is that, in basic relativity theory, or as in Special Relativity, “light speed” is in some ways a lot what you might think of for an *infinite* speed.

<<

So photons are traveling at an infinite speed. I think not.

>>

For one thing, the vacuum light speed sets a kinetic limit on accelerating objects (as seen by a given observer), . . . In those terms, the vacuum light speed comes out as infinite “proper speed”.

<<

It appears you have some knowledge of Special Relativity’s Lorentz transformations (that some anti-science guy on another thread said Einstein “stole” from Lorentz). There are three things that happen to an object whose reference frame approaches the speed-of-light as opposed to a reference frame that isn’t: its length (in the direction of travel) contracts, its mass increases, and its clock slows down. The mass increase is what prevents particles in an accelerator from getting to the speed-of-light.

>>

Now, just thinking of speed in *that* way, doesn’t the usual definition of a black hole event horizon as a sort of ‘ultimate barrier’ start to sound either just counter intuitive, or maybe even logically outrageous?

<<

No.

>>

We assume the gravitational field is so intense that even an infinite proper speed or an infinite build up of momentum couldn’t get through?

<<

An infinite speed could get through. It’s just you can’t travel faster than c.

>>

If the black hole is rotating fast enough, do we ever get to Peeping Tom this thing?

<<

I would say, “Probably not.”

>>

Also, what in world does it mean when some physicists suggest that a black hole’s spherical event horizon must necessarily be “clothing” a hidden ‘singularity’? That singularity’s such a mythical beast that good physicists must never, ever see it?

Not only do Black Holes raise as many issues as they solve, I can’t help but think someone is eventually going to come face to face with one of those monstrous Singular points, if those are really possible?

<<

This weekend I was watching “How the Universe Works” on the Science Channel. When discussing black holes, they keep stating that the singularity is a major problem to physicists. Well, why is it that people seem to easily understand Lorentz transformations for Special Relativity and forget about time dilation near a black hole? If it takes an infinite amount of time for the singularity to form, then no singularity has formed yet in any black hole.

Let’s say you are falling into a black hole (and you aren’t ripped to shreds by the tidal forces), what would happen? As your clock is slowing down, you’ll see the rest of the Universe speed up. Assuming Hawking radiation is correct, then black holes are not eternal–they will eventually evaporate. So you’re falling into a black hole and long before you reach the singularity, the black hole evaporates.

Jim

Not fond of the title. This doesn’t prove that Einstein’s general relativity is right, although you might make a case that it proves Newton’s theory of gravity wrong. Mostly you can say it that it’s good evidence that general relativity is more accurate than Newton’s theory.

Point taken. I just copied the original, but I believe in precision of language.

So, if this orbital observation is from 26,000 years ago, do the equations predict if S2 has been assimilated by Sag A* yet, or encountered some other mischief with its neighbours?

I think it is imporant for understanding this phenomenon to state, that it is space rotating around black holes, and not just those. As the rotating black hole rotates and drags space with it (remember: space is defined by matter!), the orbiting star is moving trough space at different rotating speeds. Everytime it comes close to the black hole it takes on some of the space rotation which moves its orbit a bit further. Actually this is also why it is a phenomenon of relativity.

The same mechanism is the cause of illusionary “dark matter”. Any rotating matter drags space with it, thus causing less effective gravity to any object orbiting it. This effect is totally negligible with regard to single stars or even planets, but becomes significant with regard to galaxies and magnitudes above.

Collision of smaller and larger black holes detected by gravitational waves:

https://www.space.com/asymmetrical-black-hole-collision-gravitational-waves.html?