Messier 87 Shows Off for Hundreds of Earth-bound Astronomers

by Anne Minard on July 2, 2009

Artists's Conception of M87's inner core: Black hole, accretion disk, and inner jets. Credit: Bill Saxton, NRAO/AUI/NSF

Artists's Conception of M87's inner core: Black hole, accretion disk, and inner jets. Credit: Bill Saxton, NRAO/AUI/NSF

When the giant radio galaxy Messier 87 (M 87) unleashed a torrent of gamma radiation and radio flux, an international collaboration of 390 scientists happened to be watching. They’re reporting the discovery in this week’s issue of Science Express.

Large-scale VLA image of M87: White circle indicates the area within which the gamma-ray telescopes could tell the very energetic gamma rays were being emitted. To narrow down the location further required the VLBA. CREDIT: NRAO/AUI/NSF

Large-scale VLA image of M87: White circle indicates the area within which the gamma-ray telescopes could tell the very energetic gamma rays were being emitted. To narrow down the location further required the VLBA. CREDIT: NRAO/AUI/NSF

The results give first experimental evidence that particles are accelerated to extremely high energies in the immediate vicinity of a supermassive black hole and then emit the observed gamma rays. The gamma rays have energies a trillion times higher than the energy of visible light.

Matthias Beilicke and Henric Krawczynski, both physicists at Washington University in St. Louis, coordinated the project using the Very Energetic Radiation Imaging Telescope Array System (VERITAS) collaboration. The effort involved three arrays of 12-meter (39-foot) to 17-meter (56-foot) telescopes, which detect very high-energy gamma rays, and the Very Long Baseline Array (VLBA) that detects radio waves with high spatial precision.

“We had scheduled gamma-ray observations of M 87 in a close cooperative effort with the three major gamma-ray observatories VERITAS, H.E.S.S. and MAGIC, and we were lucky that an extraordinary gamma-ray flare happened just when the source was observed with the VLBA and its impressive spatial resolving power,” Beilicke said.

“Only combining the high-resolution radio observations with the VHE gamma-ray observations allowed us to locate the site of the gamma-ray production,” added R. Craig Walker, a staff scientist at the National Radio Astronomy Observatory in Socorro, New Mexico.

Peering Deeper Into the Core of M87: At top left, a VLA image of the galaxy shows the radio-emitting jets at a scale of about 200,000 light-years. Subsequent zooms progress closer into the galaxy's core, where the supermassive black hole resides. In the artist's conception (background). the black hole illustrated at the center is about twice the size of our Solar System, a tiny fraction of the size of the galaxy, but holding some six billion times the mass of the Sun. Credit: Bill Saxton, NRAO/AUI/NSF

Peering Deeper Into the Core of M87: At top left, a VLA image of the galaxy shows the radio-emitting jets at a scale of about 200,000 light-years. Subsequent zooms progress closer into the galaxy's core, where the supermassive black hole resides. In the artist's conception (background). the black hole illustrated at the center is about twice the size of our Solar System, a tiny fraction of the size of the galaxy, but holding some six billion times the mass of the Sun. Credit: Bill Saxton, NRAO/AUI/NSF

M 87 is located at a distance of 50 million light years from Earth in the Virgo cluster of galaxies. The black hole in the center of M 87 is six billion times more massive than the Sun.

The size of a non-rotating black hole is given by the Schwarzschild radius. Everything — matter or radiation — that comes within one Schwarzschild radius of the center of the black hole will be swallowed by it. The Schwarzschild radius of the supermassive black hole in M 87 is comparable to the radius of our Solar System.

In the case of some supermassive black holes — as in M 87 — matter orbiting and approaching the black hole powers highly relativistic outflows, called jets. The matter in the jets travels away from the black hole, escaping its deadly gravitational force. The jets are some of the largest objects in the Universe, and they can reach out many thousands of light years from the vicinity of the black hole into the intergalactic medium.

Very high-energy gamma-ray emission from M 87 was first discovered in 1998 with the HEGRA Cherenkov telescopes. “But even today, M 87 is one of only about 25 sources outside our galaxy known to emit [very high energy] gamma rays,” says Beilicke.

The new observations now show that the particle acceleration, and the subsequent emission of gamma rays, can happen in the very “inner jet,” less than about 100 Schwarzschild radii away from the black hole, which is an extremely narrow space as compared with the total extent of the jet or the galaxy.

In addition to VERITAS and the VLBA, the High Energy Stereoscopic System (H.E.S.S.) and the Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) gamma-ray observatories were involved in these observations.

Lead image caption: Artists’s Conception of M87′s inner core: Black hole, accretion disk, and inner jets. Credit: Bill Saxton, NRAO/AUI/NSF

Second image: Large-scale VLA image of M87: White circle indicates the area within which the gamma-ray telescopes could tell the very energetic gamma rays were being emitted. To narrow down the location further required the VLBA. CREDIT: NRAO/AUI/NSF

Collage: At top left, a VLA image of the galaxy shows the radio-emitting jets at a scale of about 200,000 light-years. Subsequent zooms progress closer into the galaxy’s core, where the supermassive black hole resides. In the artist’s conception (background). the black hole illustrated at the center is about twice the size of our Solar System, a tiny fraction of the size of the galaxy, but holding some six billion times the mass of the Sun. Credit: Bill Saxton, NRAO/AUI/NSF

Sources: Science and the National Radio Astronomy Observatory, via Eurekalert.

Anne Minard is a freelance science journalist with an academic background in biology and a fascination with outer space. Her first book, Pluto and Beyond, was published in 2007.

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  • Nereid

    You mean this as a joke, right Anaconda?

    Not to get caught up in Nereid’s irrelevancies, but just one quick example: What is the mathematical definition of a “point”?

    Review the what mathematicians state themselves when asked that question and you get different definitional answers.

    Or in other words, inconsistencies.

    If you don’t intend it as a joke, then I guess there truly is no basis for any discussion.

    For the record, here’s what I said:

    [M]aths is rigorously consistent, and its foundations in logic sound. While Gödel and others proved some rather surprising results concerning the limitations of maths, for our purposes in astronomy, cosmology, and astrophysics, these limitations are irrelevant.

  • Anaconda

    Yes, I saw Nereid’s statement: “I have investigated every ‘alternative possibility’ that you have proposed…”

    Sorry, Nereid, your statement rings singularly hollow.

    As if your assurances are writ.

    The EurekAlert backs up my suggestions regarding Herbig Haro objects:

    http://www.eurekalert.org/pub_releases/2009-02/uor-fle020909.php

    And, Nereid still hasn’t addressed the physical characteristics I’ve raised with respect to this post.

    Apparently, Nereid assumes readers will accept whatever she says, but I’m not so sure about that…I think people are starting to see through Nereid’s “blocking” techniques.

  • Nereid

    AFACS, Anaconda’s first mention of “physical characteristics” comes in his very long comment on July 8th, 2009 at 3:55 pm.

    And, Nereid still hasn’t addressed the physical characteristics I’ve raised with respect to this post.

    The July 8th, 2009 at 3:55 pm comment is too long to copy, so I’ll just copy the questions in it:

    1) Are there any alternative possibilities?

    2) The first level of analysis is, “Are there any other objects that emit “jet” that are not ‘black holes’?”

    [...]

    3) Could it be that rather than “black holes” at the Active Galactic Nucleus, an object more like a “birthing” star is present?

    4) And what causes a star to have a “jet”?

    5) Could it be that the star acts a “lense” or focus of electrical energy, which concentrates a diffused electrical current and also stores it, until some unknown critical threshold is reached and then discharges the electrical energy in the form of a collimated beam of electrical energy, electrons and ions causing a magnetic field that then serves to maintain the “jet” and even causes it to “knot” and “kink” something similar to the M87 “jet”?

    (I’ve numbered these)

    The answers, again, are:

    1) No one has proposed any such, and it is very difficult to see how there could be any such, given that AGNs have a huge mass (millions to billions of sols) in a tiny volume (characteristic dimension ~hundreds of au, or smaller). I’ll be covering AGNs in more detail in a later “Nereid’s attempt to give Anaconda an insight into the nature of astronomy“.

    2) This question is nonsense (black holes do not emit jets).

    3) No; see 1) above.

    4) A very interesting question, one that is well worth exploring (but one that has nothing to do with whether an AGN could be a star).

    5) I don’t know, wrt the mechanism which gives rise to the jets observed in YSO (young stellar object; HH objects are one kind of YSO); for M87′s jet, no (see above).

    What other “physical characteristics“-based proposal has Anaconda presented, so far, in this thread? Stay tuned.

  • Nereid

    In his comment on July 8th, 2009 at 11:59 pm Anaconda proposes that plasmoids might be the things which power the jets in YSOs and AGNs:

    Nereid wrote: “but how these jets are powered shows how different they are.”
    Of course, your statement presupposes that they are powered differently. That’s called an assumption.
    But what are we actually comparing?
    The physical qualities of the resulting “jets”.
    And as electromagnetic phenonenon are scale-indepedent the size of the “jet” does not rule out an electromangetic mechanism or process.
    Nereid presents my [Anaconda's] comment: “Are there any alternative possibilities?
    And Nereid responds: “None have yet been proposed.”
    Or what she really means is: “I got my hands over my ears and I can’t hear you.”
    Because Nereid knows that plasmoids have been proposed in published journals — maybe not to her liking — but published never the less:

    After a few exchanges, it became extremely clear that plasmoids, per Bostick (1958), were not proposed as an alternative possibility (although, in fairness, I should point out that Anaconda did not comment on my observation that Bostick refers to galaxies, not AGNs, in his 1958 paper).

    There’s another long Anaconda comment on July 9th, 2009 at 12:03 pm; this seems to be the key part of it:

    Did readers actually see Nereid wrestle with the “similarities” I listed, discussing the physical characteristics by name?
    No, instead readers saw this opening:
    – A complaint that my listed physical properties were not “quantitative”.
    – A meaningless attempt to make equivalent a comparison of trees to nebulae with my comparison of the Herbig Haro objects’ “jets” to M87′s “jet”.
    – And an assumption laden assertion that, “how these jets are powered shows how different they are.”
    But no listing or discussion of the actual physical properties of the similarities I provided.
    Which is how Nereid generally proceeds: Abstract objections without ever getting to the actual physical characteristics, themselves.
    Nereid wrote: “In the case of AGNs, there is only one possible energy source; namely black holes.”
    And with Nereid’s unstated goal: End of discussion.

    (bold added)

    I really don’t know what to make of these comments Anaconda.

    You see, in your first mention you seemed to focus on the question of whether the key component of AGNs could be something other than super-massive black holes (SMBHs), and in your second you proposed an alternative (plasmoids).

    Yet in your third comment (the one I’m quoting from), you seem to have shifted your focus, to the question of what the similarities between YSO and AGN jets are.

    And indeed a later Anaconda comment seems to hint at this (July 9th, 2009 at 1:47 pm):

    DrFlimmer, I’m not saying there is a “star” at the center of M87, rather, what I am suggesting as a possibility is that the “jets” are generated by similar plasmoid processes, but on different scales.

    Now if *this* is what you mean by “addressed the physical characteristics I’ve raised with respect to this post“, then I do seem to have missed it. If so, would you please say so, directly and explicitly, and I’d be happy to help you learn more about both the observations and the theories which describe jet processes.

    (BTW, I see that DrFlimmer already commented on your ‘jet process’ proposals … but you didn’t reply).

  • Nereid

    Oops, some formatting lost in the parts of Anaconda’s comments that I quoted (in my last comment).

  • DrFlimmer

    @ Nereid:

    As you can see, I am still following ;)

    @ Anaconda:

    Would you mind answering my question? If you want to read them again:

    universetoday.com/2009/07/02/messier-87-shows-off-for-hundreds-of-earth-bound-astronomers/comment-page-3/#comment-68426

    If you are unable to answer them due to whatever reason, that would be no problem. Noone can answer all the questions. Just a short note would be nice.

    I could write a lengthy post about mathematics and their proofs and what a mathematical proof means, but I think this would lead to nowhere.
    If you (or someone else) are (is) interested in a nice and entertaining story which describes how mathematics work and why some people can’t live without it, I urge you (them) to read Simon Singh’s book “Fermat’s Last Theorem”. It is really entertaining and I really enjoyed it!

    Let’s what will be going on here. Maybe when my math test is over next Tuesday I can answer more again.

  • Anaconda

    @ DrFlimmer:

    You asked a series of questions:

    “@ Anaconda:

    Your big point is the “scale-independence” of plasmas. I have a few questions which I hope you can answer (and present some sources; I will search for my comment above later).

    Has there been produced a plasmoid in the lab with a jet?
    How much power did the jet have?
    How fast were the particles the plasmoid accelerated (in the jet)?
    What kind of radiation was detected from the accelearted particles?

    If you wonder why I ask these questions, here is my answer:
    If plasmas are indeed scaleable as high as you claim, then how big must a plasmoid be to account for the detection of VHE in M81 close to the center?
    Is it bigger or smaller than 100 Schwarzschild radii?
    If it’s smaller it has a chance.
    If it’s bigger it is ruled out, since the story above says that the radiation (and thus the acceleration of particles) took place in a region no bigger than 100 R_S.

    So, the answer to the questions above is also of interest to you!”

    Yes, your questions are reasonable, and I agree, the questions are of interest to me!

    Has a plasmoid been created in the lab with a jet?

    Not specifically identified as such. But the laboratory experiment I linked above has a “jet”, but the question unanswered was whether there was a plasmoid formed?

    http://www.eurekalert.org/pub_releases/2009-02/uor-fle020909.php

    The description in the link doesn’t give enough detail to determine if a plasmoid was at the heart of the magnetic field which generated the ‘jet”.

    I don’t have specifics.

  • Anaconda

    @ DrFlimmer:

    Continued:

    Here is another link for a “astrophysical jets” generated in a laboratory setting, but still it’s not clear if a plasmoid is responsible for the jet.

    http://www.obspm.fr/actual/nouvelle/mar08/jet.en.shtml

    Of course, the question is how large is “a region no bigger than 100 R_S.”

    I don’t have an answer at present.

    Good questions.

  • DrFlimmer

    Thanks for now, Anaconda. I will check your last link tomorrow. Now, shortly before the launch of Endeavour, just one thing:

    How big are 100 R_S?

    Well, R_S is of course the Schwarzschild radius which is defined by:

    R_S= 2*G*M/c^2

    M87′s (supposed) black hole has a mass of about 6 billion solar masses. So we gain:

    R_S= 2* 6,67*10^(-11)(m^3/(kg*s^2)) * 6*10^9*2*10^30(kg) / (3*10^8(m/s))^2 = 1.779*10^13(m)

    The letters in the brackets are of course the units of the values. So, finally:

    100 R_S = 1.779*10^15 (m)

    According to Wikipedia a light-year is about:

    1ly = 9.461*10^15 (m)

    So, 100 R_S is about 10 times smaller than one light-year. Not terribly big I would say….

  • Nereid

    @Anaconda: did you read the paper behind the webpage? It can be found by clicking on the relevant link at the bottom of the page.

    The objective of the reported research did not include an investigation of what might, or might not, be responsible for the jets; rather, it was about trying to account for the observed curving of (some) jets while also accounting for the observed properties such as shocks, speed, radiative output, and so on.

    The researchers did both lab experiments and numerical simulations; the latter used the “three-dimensional resistive MHD code GORGON” – are you familiar with it?

    Here is another link for a “astrophysical jets” generated in a laboratory setting, but still it’s not clear if a plasmoid is responsible for the jet.

    [URL omitted]

    Oh and no, no plasmoids in the research work, either by name or by implications (however, if you do find some, please let us know).

  • Nereid

    @Anaconda: as the Eureka article states, Sergey Lebedev’s team has been studying jets of astrophysical interest for several years, using a combined lab+simulation approach.

    One result of that research is reported in the l’Observatoire de Paris webpage in your later post.

    Here is another (you will have to add http://):

    arxiv.org/abs/0811.2736

    Abstract:

    Collimated outflows (jets) are ubiquitous in the universe appearing around sources as diverse as protostars and extragalactic supermassive blackholes. Jets are thought to be magnetically collimated, and launched from a magnetized accretion disk surrounding a compact gravitating object. We have developed the first laboratory experiments to address time-dependent, episodic phenomena relevant to the poorly understood jet acceleration and collimation region. The experimental results show the periodic ejections of magnetic bubbles naturally evolving into a heterogeneous jet propagating inside a channel made of self-collimated magnetic cavities. The results provide a unique view of the possible transition from a relatively steady-state jet launching to the observed highly structured outflows.

    (to be continued)

  • Nereid

    (continued)

    The number of papers from the Lebedev team, and citations thereto, are pretty good indications that this is both an active and fruitful line of research, conducted by modern astronomers.

    I did find one paper presenting an “alternative possibility”, involving plasmoids, for YSO jets: “Hypersonic Buckshot: Astrophysical Jets as Heterogeneous Collimated Plasmoids” (arxiv.org/abs/0806.0038 add your own prefix to get the URL); abstract (special characters not displayed):

    Herbig-Haro (HH) jets are commonly thought of as homogeneous beams of plasma traveling at hypersonic velocities. Structure within jet beams is often attributed to periodic or “pulsed” variations of conditions at the jet source. Simulations based on this scenario result in knots extending across the jet diameter. Observations and recent high energy density laboratory experiments shed new light on structures below this scale and indicate they may be important for understanding the fundamentals of jet dynamics. In this paper we offer an alternative to “pulsed” models of protostellar jets. Using direct numerical simulations we explore the possibility that jets are chains of sub-radial clumps propagating through a moving inter-clump medium. Our models explore an idealization of this scenario by injecting small (rrho_(jet)) spheres embedded in an otherwise smooth inter-clump jet flow. The spheres are initialized with velocities differing from the jet velocity by ~15%. We find the consequences of shifting from homogeneous to heterogeneous flows are significant as clumps interact with each other and with the inter-clump medium in a variety of ways. Structures which mimic what is expected from pulsed-jet models can form, as can previously unseen “sub-radial” behaviors including backward facing bow shocks and off-axis working surfaces. While these small-scale structures have not been seen before in simulation studies, they are found in high resolution jet observations. We discuss implications of our simulations for the interpretation of protostellar jets with regard to characterization of knots by a “lifetime” or “velocity history” approach as well as linking observed structures with central engines which produce the jets.

    I will leave it to you, Anaconda, to determine whether the “plasmoid” in the title of this paper is the same sort of thing as Bostick’s, of the same name (inconsistent definitions and all that).

    By doing a literature search, starting with the papers I have cited, you will quickly find what is already known about the similarities and differences between YSO jets and AGN ones.

    Has a plasmoid been created in the lab with a jet?

    Not specifically identified as such. But the laboratory experiment I linked above has a “jet”, but the question unanswered was whether there was a plasmoid formed?

    [URL omitted]

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