Black Holes Discharge the Energy in Their Powerful Plasma Jets Much Farther Away Than Thought

Star Torn Apart by Black Hole

In this artist’s rendering courtesy of NASA, the remnants of a star torn apart by a black hole form a disk around the black hole’s center, while jets eject from either side. The jets can travel at nearly the speed of light, and they discharge their high energy along the way. New research from UMBC in Nature Communications shows that the energy dissipation happens much farther away from the black hole’s center than previously thought. The methods for the study, standard statistical techniques and minimal reliance on assumptions from any particular jet model, make the findings difficult to dispute. The results offer clues about jet formation and structure. Credit: NASA

New study determines that black holes discharge the energy in their plasma jets much farther away from the black hole’s center than previously thought, resolving long-standing debate and offering clues to jet formation and structure.

The supermassive black holes at the centers of galaxies are the most massive objects in the universe. They range from about 1 million to upwards of 10 billion times the mass of the Sun. Some of these black holes also blast out gigantic, super-heated jets of plasma at nearly the speed of light. The primary way that the jets discharge this powerful motion energy is by converting it into extremely high-energy gamma rays. However, UMBC physics Ph.D. candidate Adam Leah Harvey says, “How exactly this radiation is created is an open question.”

The jet has to discharge its energy somewhere, and previous work doesn’t agree where. The prime candidates are two regions made of gas and light that encircle black holes, called the broad-line region and the molecular torus.

A black hole’s jet has the potential to convert visible and infrared light in either region to high-energy gamma rays by giving away some of its energy. Harvey’s new NASA-funded research sheds light on this controversy by offering strong evidence that the jets mostly release energy in the molecular torus, and not in the broad-line region. The study was published in October in Nature Communications and co-authored by UMBC physicists Markos Georganopoulos and Eileen Meyer.

Far out

The broad-line region is closer to the center of a black hole, at a distance of about 0.3 light-years. The molecular torus is much farther out—more than  3 light-years. While all of these distances seem huge to a non-astronomer, the new work “tells us that we’re getting energy dissipation far away from the black hole at the relevant scales,” Harvey explains.

“The implications are extremely important for our understanding of jets launched by black holes,” Harvey says. Which region primarily absorbs the jet’s energy offers clues to how the jets initially form, pick up speed, and become column-shaped. For example, “It indicates that the jet is not accelerated enough at smaller scales to start to dissipate energy,” Harvey says.

Other researchers have proposed contradictory ideas about the jets’ structure and behavior. Because of the trusted methods Harvey used in their new work, however, they expect the results to be broadly accepted in the scientific community. “The results basically help to constrain those possibilities—those different models—of jet formation.”

On solid footing

To come to their conclusions, Harvey applied a standard statistical technique called “bootstrapping” to data from 62 observations of black hole jets. “A lot of what came before this paper has been very model-dependent. Other papers have made a lot of very specific assumptions, whereas our method is extremely general,” Harvey explains. “There isn’t much to undermine the analysis. It’s well-understood methods, and just using observational data. So the result should be correct.”

A quantity called the seed factor was central to the analysis. The seed factor indicates where the light waves that the jet converts to gamma rays come from. If the conversion happens at the molecular torus, one seed factor is expected. If it happens at the broad-line region, the seed factor will be different.

Georganopolous, associate professor of physics and one of Harvey’s advisors, originally developed the seed factor concept, but “applying the idea of the seed factor had to wait for someone with a lot of perseverance, and this someone was Adam Leah,” Georganopoulos says.

Harvey calculated the seed factors for all 62 observations. They found that the seed factors fell in a normal distribution aligned almost perfectly around the expected value for the molecular torus. That result strongly suggests that the energy from the jet is discharging into light waves in the molecular torus, and not in the broad-line region.

Tangents and searches

Harvey shares that the support of their mentors, Georganopoulos and Meyer, assistant professor of physics, was instrumental to the project’s success. “I think that without them letting me go off on a lot of tangents and searches of how to do things, this would have never gotten to the level that it’s at,” Harvey says. “Because they allowed me to really dig into it, I was able to pull out a lot more from this project.”

Harvey identifies as an “observational astronomer,” but adds, “I’m really more of a data scientist and a statistician than I am a physicist.” And the statistics has been the most exciting part of this work, they say.

“I just think it’s really cool that I was able to figure out methods to create such a strong study of such a weird system that is so removed from my own personal reality.” Harvey says. “It’s going to be fun to see what people do with it.”

Reference: “Powerful extragalactic jets dissipate their kinetic energy far from the central black hole” by Adam Leah W. Harvey, Markos Georganopoulos and Eileen T. Meyer, 30 October 2020, Nature Communications.
DOI: 10.1038/s41467-020-19296-6

11 Comments on "Black Holes Discharge the Energy in Their Powerful Plasma Jets Much Farther Away Than Thought"

  1. I love being informed on cutting edge technologies and especially physics and cosmology also astronomy and observational analysis.

  2. I thought nothing could escape a black hole.. im not educated in this but can someone explain how jets of gas can shoot out but light cant..

    • Torbjörn Larsson | December 26, 2020 at 8:47 am | Reply

      “I thought nothing could escape a black hole.. im not educated in this but can someone explain how jets of gas can shoot out but light cant..”

      Black hole physics is complex and mostly tentative at the moment, so bear with me.

      It is true that infalling objects do not escape the so called event horizon of the black hole (hence its name – we can’t see what happens within), but physicists has uncovered that it is likely thermal radiation (so called Hawking radiation) gets out. This means black holes are not thermodynamic oddities but presumably has a temperature, entropy and a finite lifetime – however except for the later stages of the thermal radiation evaporating black holes is the presumed radiation much energetic and into the visible glowing range.

      Now to the jets. My longer comment contains some of the basis for that in the Active Galaxy Nuclei [AGN] structure that is the central super massive black hole [SMBH] driven energetic core of a jet active galaxy. The accretion disk gas and dust matter – the matter that has fallen towards the galactic core center – is funneled onto the black hole. Most of the infalling matter disappears as you say, but it is heated and ionized to X-ray and charged particle emitting plasma before it falls in.

      If the black hole has a smidgen of magnetic field – it can be slightly net charged after all, if charged matter has fallen into it – it is vastly amplified by the black hole gravity and spin twisting it [ https://en.wikipedia.org/wiki/Astrophysical_jet ].

      “One explanation is that tangled magnetic fields[2] are organised to aim two diametrically opposing beams away from the central source by angles only several degrees wide (c. > 1%).[3] Jets may also be influenced by a general relativity effect known as frame-dragging.”

      Now we come to an explicitly open question of one, the other or both alternatives:

      “However, the frequency of high-energy astrophysical sources with jets suggest combinations of different mechanisms indirectly identified with the energy within the associated accretion disk and X-ray emissions from the generating source. Two early theories have been used to explain how energy can be transferred from a black hole into an astrophysical jet:

      – Blandford–Znajek process.[14] This theory explains the extraction of energy from magnetic fields around an accretion disk, which are dragged and twisted by the spin of the black hole. Relativistic material is then feasibly launched by the tightening of the field lines.

      – Penrose mechanism.[15] Here energy is extracted from a rotating black hole by frame dragging, which was later theoretically proven to be able to extract relativistic particle energy and momentum,[16] and subsequently shown to be a possible mechanism for jet formation.”

      I’m not an expert on this, just long interested in cosmology: caveat emptor applies. However, I can safely say Good Continued Yule!

      • Torbjörn Larsson | December 26, 2020 at 8:54 am | Reply

        To be more technically correct, the black hole thermal radiation is generated within a miniscule distance (so called Planck length) from outside the event horizon – the event horizon is still a classic “one way ticket” to the inside.

      • Torbjörn Larsson | December 26, 2020 at 9:01 am | Reply

        Also, and sorry about confusing you but I was confused myself, the accretion disk magnetic field is supposedly the main culprit. (And I think those have been observed.) Again, heating would ionize some of the gas and a rotating charged disk would generate a field. That is much more sound than what I proposed for magnetic field.

        If the disk magnetic field gets anywhere near the black hole, the rest of the basis for the Blandford–Znajek process follows though.

    • Good question I would also like to ask what is plasma doing shooting out of a singularity anyways ?

  3. Vivian Robinson | December 25, 2020 at 4:01 pm | Reply

    It is surprising how much people make advances out of nothing. Einstein did not believe in black holes. His 1916 paper on the Foundations of the General Theory of Relativity shows he introduced approximations to derive his field equations. Exact solutions to approximations are still approximations. Equations which predict black holes require two mathematical errors beyond Einstein’s approximations to get that result. More details can be found at:-

    https://quicycle.com/video/qc0106-dr-vivian-robinson-the-physics-of-einsteins-gravity/ OR
    https://www.youtube.com/watch?v=86mb-D_Sla4&feature=emb_logo

    Mathematicians who believe in black holes don’t understand Einstein’s mathematics. In particular they seem not to understand that the term 1 – x is a good approximation to the term 1/(1 + x) when x << 1.
    Physicists who believe in black holes don't understand simple physics. It is not physically possible for an orbiting body to have it perihelion precess and for gravity to be stronger than inverse square law. Newton pointed that out in 1687.

    The above presentation gives an exact solution to the physics Einstein used when he developed his gravitational field equations. That solution predicts the structure observed by the Event Horizon Telescope collaboration. It makes it easy to explain why massive objects can shoot out jets perpendicular to its plane of rotation.

    • Torbjörn Larsson | December 26, 2020 at 8:19 am | Reply

      That is a self promotion link to a pseudoscience source.

      I’m not sure how to view your attempt to use the good name of science, peer review and Cambridge University, but it looks worse than the usual pseudoscience peddling.

      Your own description implies you don’t solve the Einstein equations or do anything of the work that the Event Horizon Telescope collaboration did when they showed the world the firs black hole shadow image. Consequently the 2020 Nobel Prize in Physics was rewarded to 3 discoverers of black hole physics and the Milky Way central Super Massive Black Hole [ https://www.nobelprize.org/prizes/physics/2020/summary/ ].

  4. Torbjörn Larsson | December 26, 2020 at 8:01 am | Reply

    They use a bootstrap sample based on statistical reconstructions of a couple of well studied systems, but the bootstrap statistics looks good.

    The seed factor describes how much inverse Compton scattering producing high-energy photons from electrons happens in relation to the jet synchrotron radiation produced by jet electrons, proxied by a ratio of light wavelength amplitudes. That too looks good.

    “Our finding sets specific constraints on jet models: there is no substantial steady-state jet energy dissipation at scales less than ~1 pc. Within this distance the flow has to collimate and achieve an opening angle of a few degrees, and at the same time accelerate to bulk Lorentz factors of 10–50, as required by VLBI studies25. Major particle acceleration and subsequent dissipation of the order of 10% of the jet power26 must take place beyond the sub-pc broad-line region and within the ~pc scale molecular torus. This conclusion does not rest on any single source, but rather on clear observables for an entire population of powerful jets.”

    “Our result also argues that the VLBI core is not the dominant location of gamma-ray emission.”

    A typical model of AGN structure [see Fig.1 at the link]:

    “The typical AGN is made of several components (see Fig. 1 on the right):
    -An accretion disk where matter is funneled onto the SMBH.
    -A broad line region (BLR) where the broad and optical/UV lines are produced. Reverberation mapping studies have shown that the inner radius of this region scales with the luminosity and is ~10-100 light days (e.g., Kaspi et al. 2005).
    -A molecular torus, which is located within few parsecs from the SMBH. Near-IR reverberation studies have shown that the inner radius of the torus also scales with the luminosity (Suganuma et al. 2006).
    -A narrow line region (NLR), which is located at ~100-300 pc from the SMBH, where the narrow optical lines are created.”
    [ http://www.isdc.unige.ch/~ricci/Website/Active_Galactic_Nuclei.html ]

    I have seen newer variants where the components line up differently, with the jets going at angles to the disk torus et cetera, but the general idea is there.

  5. … The Universe is more puzzling than we anticipate, this is just an example of a recycle bin at its best…
    … perfect tic-tock…
    … a super human anticipation, though…

  6. If black holes can emit anything, why not light? I think that black holes are just the gravitational center of all the energy in the galaxy.

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