New observations solve a 30-year-old puzzle of mysterious signals from around black holes.

An artist's conception of a supermassive black hole. NASA/JPL-Caltech
An artist's conception of a supermassive black hole.

Strange things happen around black holes, especially spinning ones. Their strong gravitational pull means they don’t just pull in gas to munch on — they drag the very fabric of spacetime around them as they spin.

Every rotating massive body does this — even puny Earth, as measured by the Gravity Probe B. But around black holes the so-called frame-dragging effect (also known as the Lense-Thirring effect) is particularly strong. Like flies stuck in honey, anything embedded in that spacetime will get dragged along, too. And now, with new observations from the XMM-Newton and NuSTAR space telescopes, astronomers have connected the effect to long-mysterious signals seen around stellar-mass black holes.

Black Hole Beats

Quasi-Periodic Oscillation
This artist's impression depicts an accretion disk surrounding a black hole. The black hole drags spacetime with it as it spins. So X-ray-emitting plasma near the black hole, stuck in spacetime like a fly stuck in honey, precesses. The X-rays strike matter in the surrounding disk, making it to glow like a fluorescent bulb. The glow appears to rotate around the accretion disc to the right (top), to the front (middle), and to the left (bottom).
ESA / ATG medialab

While we can’t see black holes directly, we can see those that are guzzling gas. Such meals are easy to come by for black holes in binary systems, as they pull mass from their unlucky companion stars. As the gas spirals inward, it heats up: the closer it comes to the black hole, the hotter the gas will be, and the higher the frequency of the photons it radiates. Very near the black hole, the plasma reaches a fevered pitch, puffing up and emitting energetic X-rays.

Back in the 1980s, astronomers started seeing signals amidst these flickering X-rays that looked suspiciously regular. Dubbed quasi-periodic oscillations, these QPOs seemed to come from something whizzing intriguingly close-in around the black hole. More than a decade later, an idea emerged: astronomers could be witnessing the frame dragging effect in action.

Here’s the general picture: hot puffed-up plasma very near the black hole radiates X-rays. Some of these X-rays hit the surrounding gas disk, knocking electrons off of iron atoms in the swirling gas. As those iron atoms snatch back their electrons, they fluoresce, emitting X-rays at a specific energy.

The whole system — the black hole, the hot inner plasma, and the surrounding disk — is spinning like a top. And if the disk is tilted relative to the black hole, then the top will wobble, or precess. We’ll see the hot plasma fluoresce off of part of the outer disk, and that fluorescence will appear to rotate around the black hole. When we’re seeing a part of the disk spinning around toward Earth, we’ll see its iron emission blueshifted; emission from a part of the disk spinning away again will shift redward.

Adam Ingram (University of Amsterdam, The Netherlands) and colleagues set out to observe this effect directly. They pointed the XMM-Newton and NuSTAR space telescopes at the system known as H1743-322, where a black hole with a mass of about 10 Suns is drawing in gas from its companion star. Four of the five observations clearly show the iron line shifting back and forth in the spectrum over the course of 4 to 5 seconds, exactly in the way that the frame-dragging effect predicts.

“This is a very intriguing result,” says Laura Brenneman (Harvard-Smithsonian Center for Astrophysics), who was not involved with the study. “Certain types of QPOs in X-ray[-emitting black hole] binaries have long been suspected to arise from some form of precession, but this result is the closest thing I've seen to hard evidence for that.”

This result turns stellar-mass black holes into a proving ground for new physics. “If you can get to the bottom of the astrophysics, then you can really test general relativity,” Ingram said in NASA’s press release, welcome news to physicists who are searching for a deeper theory of gravity.

One of These Is Not Like the Others

Over 3 days’ worth of exposure, XMM-Newton collected five sets of data. While four of these matched beautifully, one, known as orbit 1b, didn’t conform at all to expectations. It could simply be that some gas obstructed the astronomers’ view, or it could be that the observation is telling astronomers something more fundamental.

“I am curious as to what is going on in XMM-Newton’s orbit 1b that is so anomalous compared to the others,” Brenneman adds, “but I don't think it diminishes the result at all, just adds an extra dimension and opens up more questions.”

Another intriguing aspect of QPOs is that they’ve (almost) never been seen in the supermassive variety of black holes. These active galactic nuclei (AGN) guzzle gas at the center of galaxies with the same setup as stellar-mass black holes: a black hole, a gas disk, and X-ray-emitting plasma. The only thing they’re missing is the binary companion star.

“There has only been one reputable claim of a QPO in an AGN back in 2008, and it hasn't been seen again since,” Brenneman says. “If there were QPOs-a-plenty in AGN, we would likely have detected them by now.” Why they aren’t there, no one knows.

With one mystery solved, it’s clear there are still more cases awaiting closure.


Adam Ingram et al. "A quasi-periodic modulation of the iron line centroid energy in the black hole binary H 1743-322", Monthly Notices of the Royal Astronomical Society, 2016 May 25.(Full text)


Image of Lindsay


July 22, 2016 at 9:14 pm

Thank you Monica. This is a fascinating finding. You caught my attention with your statement:
"[black holes] drag the very fabric of spacetime around them as they spin." I pictured a black hole somehow pulling the space-time-mass-energy universe into its core (I know you said 'around,' but I often jump to unjustified conclusions. I had to look up the wiki definition for frame-dragging effect of General Relativity. Now I know this is not what you meant. But I found it equally interesting that "This effect is analogous to the hyperfine structure in atomic spectra due to nuclear spin."

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Image of Yehiel Gotkis

Yehiel Gotkis

January 19, 2017 at 10:13 pm

Surprised? I am not at all... This is why:

Liquid vortex (LV) sheds light on the essentials of the black holes (BHs).

Introduction. Vortices could be found everywhere around us. Assuming different kinds of vortices possess common generics, one can get an insight in understanding the hardly accessible and/or observable ones, for instance BHs, by observing the easily accessible ones, for example LVs. Exploring LVs, also, allows to run the observations with reasonable resources, in reasonable time, under variety of conditions and, what is especially important, to observe the developments beneath the funnel bottom, which in reference to the BHs can be considered, in a way, as being an analog of the BH bottom.
The LV I’ve observed was located in the middle of a reasonably large and calm water pool It was arranged to confine its developments predominantly in the water thin surface layer thus making it to act as a two-dimensional rather than a tri-dimensional one and, thanks to it, to consider the developments as likely related to the BH associated ones. The collection of LV videos recorded under a variety of conditions could be accessed at YouTube under my name Yehiel Gotkis.
Thorough scrutiny of the LV observations lead, along with relatively trivial things, to a shocking grasp, questioning even the widely-adopted views on the existence of the dark matter and dark energy.
Observations, analysis, interpretations and conclusions.
• LV was observed to emit outgoing double-spiral waves, which, oppositely to concentric waves, carry momentum (and the associated kinetic energy) transferable to the distant material objects. The cause inducing the double spiral appearance was found to be associated with asymmetry of the funnel bottom, which was observed to be most of the time shaped as a spinning distorted digit 8. The fact that an asymmetry in the funnel of the spinning LV, and probably the BH, cause generation of propagating away spiral, in the case of BH gravitational, waves, indicates that spinning BHs continuously re-emit part of the acquired mass/energy back into the space as gravitational waves. Which, in long (cosmic) timescale, may make a significant amount of it. Also, meaning that the Universe should be filled with the energetic gravitational ripples (gravitational noise). As the ripples over the surface of the ocean.
• Also, the LV spinning double spiral wave geometry and the associated image wobbling when observed from a particular direction (check my related YouTube video named “Liquid vortex upper double spiral wave generation”) may provide a natural explanation to the Quasi Periodic Oscillation (QPO) phenomenon known for the BHs.
• The LV observed, being naturally sucking the liquid, was pulling-in together with it also whatever was floating over the water surface: foam, dry leaves, all kinds of light debris, which is not a surprise... However, in relation to the BHs, the upper surface of the water pool could be thought to be associated with the spacetime and the floating stuff - with the regular matter. For the spacetime-regular matter duo
• The spacetime and the matter are inherently mutually engaged
following each other’s movement.
This mutual matter-spacetime engagement could be guessed of causing effects analogous to hydrodynamic drag and friction - gravitational drag and gravitational friction in this case. Staying within the frame of the above rationale, we have to conclude that
The BHs are to be thought of being pulling-in not only the surrounding regular matter but also the spacetime, whirling around the BH as liquid whirls around the LV (furthermore abbreviated as BHSSR, Black Hole Sucking Spacetime Rationale).
Intriguingly, the BHSSR allows to interpret the legendary galaxy rotation curves anomaly and the Universe accelerated expansion with no necessity of introducing the two famous but still challenging to prove hypotheses:
Existence of the dark matter\
As per the BHSSR, the pulled-in by the BH whirling spacetime can add additional momentum to the rotation of the visible matter in the BH proximity,
Existence of the dark energy
As per the BHSSR, at the galactic periphery, where the pulling-in gravitational force is diminished, the keeping on centrifugal force, induced by the spinning spacetime, helps accelerating the regular matter away from the galaxy center.

• Another important LV occurrence is associated with the development of galaxy-like spiral shape when a handful of floating shredded dry leaves was spread over the vortex area (video at
The deep significance of this development stirred my mind and I would like to share it here:
The floating shredded leaves were always quickly arranging in a spiral galaxy-like shape. What could drive the initially disarranged flock of shredded intellect-less dry leaves to organize themselves in a spiral shape? How could they know about the spiral geometry to follow?
With the knowledge acquired about the LV, the answer looks obviously clear to me now… It is the water whirling around the LV, managing the shredded stuff to arrange itself in the spiral shape. The complex spiral structure would never be established if not being governed by the whirling water flows.
This important deduction being applied to the galaxies leads to an unambiguous conclusion about what may drive formation of their spiral geometry: if in a system A, made of non-continuous media a spiral structure is revealed, it must be postulated that there is an adjoined with A partnering system B made of continuous media or containing a continuous media component. Since continuous media is essential for developing a vortex and an associated whirling activity. With regard to the galaxies, the only component to be considered as being of continuous nature is the spacetime, which, being actuated by the BH vortex to whirlingly spin around and pulled into BH funnel, will function as the supporting adjoined system B. So,
The BH vortex actuates the spacetime to whirlingly spin around and flow into it, and the whirling spacetime, in its turn, “directs” the galactic regular matter to arrange itself in a spiral shape.
And refraining on the spacetime/matter tandem relations:
The matter and the spacetime are likely adhered to each other as an inseparably engaged duo: where the spacetime there the matter. And vice versa.
This is it. Thank you for your attention.

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Image of Esnuka


May 28, 2017 at 4:23 pm

I believe there is no frame-dragging effect of gravity on mass, only on electromagnetic energy!
Curiously, the Lense-Thirring effect in Gravity Probe B has the same value than the geodetic effect of the Earth around the Sun.
Kinetic energy of a rotating body like Earth will increase gravity but more in the sense of classical force than classical aether!
NASA error?
Understanding Gravity Probe-B experiment without math

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