# M87’s Jet (and Memories of Clarke)

The massive galaxy M87, the central object of the Virgo cluster, has drawn our attention for a long time. It was in 1918 that Heber Curtis discovered a jet pushing at least 5000 light years away from the center of the galaxy. In 1949, the radio source Virgo A was identified with M87, and by the 1960s it was believed that the jet was actually two sided, its one-sided appearance due to relativistic Doppler beaming, which increased the luminosity of the jet in the direction of the observer.

That latter point was confirmed by recent observations using the Very Long Baseline Array (VLBA), with a resulting image showing detail down to a resolution of one milli-arcsecond. Some fifty times better than what Hubble can manage at optical wavelengths, the radio image (seen below in false color) shows the faint counter-jet structure that had been posited by the Russian astrophysicist Iosif Shklovsky. The latter noted that the jet liberated as much energy as the explosion of ten million supernovae.

Image: The Inner Jet of the Radio Galaxy M87 located in the Virgo cluster. The angular resolution of this false-color radio image observed by the VLBA at 2 cm wavelength is approximately one milli-arcsecond, fifty times better than that of the Hubble Space Telescope at optical wavelengths. The image shows a limb brightened jet and a faint counter-jet. The central gap is consistent with the presence of a fast inner jet which is beamed away from the observer surrounded by a slower moving outer plasma seen by the VLBA. Credit: Y.Y. Kovalev, MPIfR Bonn.

The apparent mechanism in all this is a supermassive black hole in the center of the galaxy. The rapidly rotating accretion disk surrounding it feeds the hole, while matter is ejected from the nucleus in the observed jets. Of course, a playful look for macro-engineering might suggest alternative explanations. M87 fascinated Arthur C. Clarke, who wrote about it in a book called The Scientist Speculates: An Anthology of Partly-Baked Ideas (New York: Capricorn Books, 1962), likening it to a scenario he had painted in his 1954 novel The City and the Stars:

Man was about to leave his Universe, as long ago he had left his world. And not only Man, but the thousand other races that had worked with him to make the Empire. They were gathered together, here at the edge of the Galaxy, with its whole thickness between them and the goal they would not reach for ages.

They had assembled a fleet before which imagination quailed. Its flagships were suns, its smallest vessels planets. An entire globular cluster, with all its solar systems and all their teeming worlds, was about to be launched across infinity.

The long line of fire smashed through the heart of the Universe, leaping from star to star. In a moment of time a thousand suns had died, feeding their energies to the monstrous shape that had torn along the axis of the Galaxy and was now receding into the abyss . . .

It’s that last line that seizes the attention, a galactic jet’s inconceivable energies created by artificial means. Clarke later noted in a postscript to the reprint of this essay in Cosmic Search magazine that he had written it before the realization that explosive events tied to such active galactic nuclei (AGN) seem to be common in the universe. He also gave a nod both to Freeman Dyson and to Stanley Schmidt’s chilling line in The Sins of the Fathers (1976) that “Seyfert galaxies are industrial accidents.”

Now we have a better look at the central region of M87 than ever before, one corresponding to a linear resolution of three light months. Adding the Effelsberg 100m radio telescope to provide a trans-Atlantic baseline should provide an even more detailed image of the galaxy’s jet. An industrial accident it’s doubtless not, nor is it evidence of extraterrestrial engineering, but what a magnificent natural phenomenon grows out of the tortured interactions at this galaxy’s heart.

Comments on this entry are closed.

• Adam October 19, 2007, 20:46

Hi Paul

In the deep future the galaxies themselves will need to be re-engineered to provide power for life. Regular star formation will grind to a halt about 100 trillion years from now when the ISM will be too rich in “metals” to produce fusing stars. The only sources of untouched fusion fuel will be brown dwarfs and low-mass white-dwarfs – these can be collided and merged to ignite and produce energy. Newly born red dwarfs will be the brightest things in the Universe by that stage.

After that the last energy sources from stars will be WIMP annihilation and induced proton-decay, both of which might be controlled and enhanced sufficiently for life. Beyond that what remains is carefully managing the accretion of mass by black holes to extract their rotational energy – and merging the holes will allow more energy extraction still.

So I wonder are Seyfert galaxies experiments in black hole husbandry gone horribly awry? Probably not, but as the aeons of aeons grind the galaxies into dust I wonder what might come of those galactic black holes.

In the Omega Point eschatology intelligent life has to disassemble the galaxies and produce mass depletions in the cosmos in two opposite directions, concentrating the rest of the mass in the remaining four directions – eventually those depleted directions become cosmic heat-sinks for powering Life during cosmic recollapse. Tipler’s new formulation requires the baryonic mass to be annihilated almost totally to bring about recollapse by dropping the Higgs field into its true vacuum state. Just what Life must do with excess energy produced is a puzzle – beam it away from the heat-sink directions? Perhaps ultra-perfect mirrors can deflect heat towards them?

• Administrator October 20, 2007, 13:41

Adam, long-term thinking indeed! In addition to these Tiplerian ideas, I’m sure you’re familiar with The Five Ages of the Universe, by Fred Adams and Greg Laughlin, a mind-bending take on deep time and where the universe is going. And I love that notion of ‘black hole husbandry,’ by the way. As to that excess energy, I wonder what Clarke in his prime might have done with it. Or maybe even now, though I’ve heard he’s stopped active writing.

• Adam October 20, 2007, 17:00

Hi Paul

Indeed – their book and the Astrophysical Journal paper that preceded it are compulsory reading for anyone with an interest in physical eschatology.

As for Clarke he has certainly written some of the most evocative far future SF out there, that makes me wonder who can take his mantle. SF has a very different set of tropes to the rather simple-minded stuff of the 1930s-50s that he grew out of – in part due to his own efforts. Space-travel and the planets were utterly unlike the SF tales in ways no one imagined. Doubtless the Future Universe will be as misbehaved.

• Steve October 21, 2007, 0:05

I love this article, in fact this blog! I have often wondered: could we *really* be sure we would recognize galactic engineering on such a grand scale? I think it was Clarke who said, “A sufficiently advanced technology would be indistinguishable from magic.” I’ve wondered if such a technology might be indistinguishable from *Nature*. That is, their technology should be able to utilize natural forces far more than ours, and might *look* more natural.

I wrote a speculative piece to that effect on my blog, http://www.culturalconscience.com called, “Dreaming The Incredible – What If?”
in the “Science and the Environment” Category.

• Administrator October 21, 2007, 8:22

Steve, glad to have you here and thank you for the kind words. I enjoyed your blog piece and it reminded me of Michio Kaku’s statement that if we did ever run into a Kardashev Type III civilization, we would be about as likely to recognize its handiwork as an ant colony would be to make sense out of the superhighway running by it here on Earth. Others, of course, argue that massive engineering would be obvious, but as you say, and I think rightly, it may actually mirror nature in ways that we can’t yet understand. Fascinating speculation…

• forrest noble November 4, 2007, 2:20

Hello fellow space enthusiasts,

loved that science fiction piece above. Amost seems poetic. The conclusion “the tortured interactions at this galaxy’s heart.” I see it differently however. In contrast to current BB theory, etc. What I think you’re seeing in these jets is the act of atomic particle creation itself, electrons, protons some alpha particles and (some anti-matter) primarily positrons (i.e. there was no BB). All basic atomic particles are accordingly created in this way– that most of the stars of a galaxy were built from the material of the central “Black Hole” (which was slowly built from the surrounding dark matter field). It is not a vacuous single point as in most theories but is instead a very compressed form of dark matter. Another state of “dark matter” that accordingly is thousands of times more dense than a theoretical Neutron Star. In their formative stages, and before there were stars in the galaxy, all galactic black holes produced these large jets which created the matter for the star formations in the galaxy, essentially creating the entire galaxy (rather than solely a “Thanksgiving Goggler” that they are currently perceived to be.

Similar but obviously much smaller jets can be observed emanating from some large stellar black holes. Essentially the black hole is radiating away its mass in the form of newly created matter ( you might call it a large version of Hawkings radiation if you like). Large galaxies like M87 can get a new infusion of matter in the form of consuming stars or by assimilating large galactic or formerly large intergalactic clouds.

New matter, like Fred Hoyle predicted, is being created all the time, even though his theory of an infinite universe is probably not correct — his Steady State Theory was, I believe, closer to the truth than the current BB theory which I think it is all wet– nearly 100% wrong.

Prediction: No matter how far we look back in time with more advanced detection capabilities we will continue to see older and more red-shifted galaxies that will easily exceed the present 13.7B year old estimates of the age of the BB universe, essentially refuting the BB. I’m hoping they will figure it out soon (an alternative) and dump the BB in at least the next 20 years.

Respectfully forrest

• ljk December 18, 2007, 15:36

MHD models and synthetic synchrotron maps for the jet of M87

Authors: J. Gracia, S. Bogovalov, K. Tsinganos

(Submitted on 17 Dec 2007)

Abstract: We present a self-consistent MHD model for the jet of M87. The model consist of two distinct zones: an inner relativistic outflow, which we identify with the observed jet, and an outer cold disk-wind. While the former does not self-collimate efficiently due to its high effective inertia, the latter fulfills all the conditions for efficient collimation by the magneto-centrifugal mechanism. Given the right balance between the effective inertia of the inner flow and the collimation efficiency of the outer disk wind, the relativistic flow is magnetically confined into a well collimated beam for a wide range of parameters and matches the measurements of the opening angle of M87 over several orders of magnitude in spatial extent.

In the second part of this work, we present synthetic synchrotron emission maps for our MHD models. In principle the two-zone model can reproduce the morphological structure seen in radio observations, as central-peaked profiles across the jet close the the source, limb-bright further down the jet, and a bright knot close to the position of HST-1. However it is difficult to reconcile all features into a single set of parameters.

Comments: 4 pages, 5 figures, to appear in the proceedings of the HEPRO conference, September 24-28, 2007, Dublin, Ireland

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0712.2734v1 [astro-ph]

Submission history

From: Jose Gracia [view email]

[v1] Mon, 17 Dec 2007 15:12:41 GMT (327kb)

http://arxiv.org/abs/0712.2734

• ljk January 7, 2008, 10:59

Spine-sheath layer radiative interplay in subparsec-scale jets and the TeV emission from M87

Authors: F. Tavecchio, G. Ghisellini (INAF – Osservatorio Astronomico di Brera, Italy)

(Submitted on 3 Jan 2008)

Abstract: Simple one-zone homogeneous synchrotron self-Compton models have severe difficulties in explaining the TeV emission observed in the radiogalaxy M87. Also the site of the TeV emission region is uncertain: it could be the unresolved jet close to the nucleus, analogously to what proposed for blazars, or an active knot, called HST-1, tens of parsec away.

We explore the possibility that the TeV emission of M87 is produced in the misaligned subpc scale jet. We base our modelling on a structured jet, with a fast spine surrounded by a slower layer. In this context the main site responsible for the emission of the TeV radiation is the layer, while the (debeamed) spine accounts for the emission from the radio to the GeV band: therefore we expect a more complex correlation with the TeV component than that expected in one-zone scenarios, in which both components are produced by the same region. Observed from small angles, the spine would dominate the emission, with an overall Spectral Energy Distribution close to those of BL Lac objects with a synchrotron peak located at low energy (LBLs).

Comments: 5 pages, 2 figures. Accepted for publication in MNRAS Letters

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0801.0593v1 [astro-ph]

Submission history

From: Gabriele Ghisellini [view email]

[v1] Thu, 3 Jan 2008 21:00:15 GMT (41kb)

http://arxiv.org/abs/0801.0593

• ljk March 3, 2008, 9:52

Spins of the supermassive black hole in M87: new constraints from TeV observations

Authors: Jian-Min Wang (1), Yan-Rong Li (1), Jain-Cheng Li (2), Shu Zhang (1) (1. IHEP, Beijing, 2. YNO, Kunming)

(Submitted on 29 Feb 2008)

Abstract: The rapid TeV $\gamma-$ray variability detected in the well-known nearby radio galaxy M87 implies an extremely compact emission region (5-10 Schwarzschild radii) near the horizon of the supermassive black hole in the galactic center. TeV photons are affected by dilution due to interaction with the radiation field of the advection-dominated accretion flow (ADAF) around the black hole, and can thus be used to probe the innermost regions around the black hole. We calculate the optical depth of the ADAF radiation field to the TeV photons and find it strongly depends on the spin of the black hole. We find that transparent radii of 10 TeV photons are of $5R_{\rm S}$ and $13R_{\rm S}$ for the maximally rotating and non-rotating black holes, respectively.

With the observations, the calculated transparent radii strongly suggest the black hole is spinning fast in the galaxy. TeV photons could be used as a powerful diagnostic for estimating black hole spins in galaxies in the future.

Comments: 4 pages, 4 figures. to appear in ApJL

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0802.4322v1 [astro-ph]

Submission history

From: Jian-Min Wang [view email]

[v1] Fri, 29 Feb 2008 04:55:28 GMT (33kb)

http://arxiv.org/abs/0802.4322

• ljk March 14, 2008, 14:43

Imaging a Jet Base – Prospects with M87

Authors: R. Craig Walker, Chun Ly, William Junor, Phillip E. Hardee

(Submitted on 12 Mar 2008)

Abstract: M87 provides the best opportunity to study the base of a jet where it is collimated and accelerated. The size of that region scales with the mass of the black hole, and M87 has the best combination of high mass, proximity to the Earth, and presence of a bright jet. VLBI observations of M87 can probe regions under 100 gravitational radii where theoretical studies suggest that the jet formation and acceleration occurs.

A one-year sequence of 43 GHz observations every 3 weeks on the VLBA is being used to study the structure and dynamics in this region. Initial results from that effort are reported here, including the observation of rapid motions – sufficiently rapid that more frequent observations are planned for early 2008. The contribution ends with a discussion of prospects for future VLBI observations of M87 with VSOP2. For VSOP2, a strong recommendation is made that a series of daily observations at 43 GHz be planned.

Comments: To be included in the proceedings of the symposium “Approaching Micro-Arcsecond Resolution with VSOP-2: Astrophysics and Technology”, 6 pages with 2 figures

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0803.1837v1 [astro-ph]

Submission history

From: Chun Ly [view email]

[v1] Wed, 12 Mar 2008 20:06:30 GMT (303kb)

http://arxiv.org/abs/0803.1837

• ljk May 29, 2008, 13:10

Particle acceleration close to the supermassive black hole horizon: the case of M87

Authors: F.M. Rieger, F.A. Aharonian

(Submitted on 27 May 2008)

Abstract: The radio galaxy M87 has recently been found to be a rapidly variable TeV emitting source. We analyze the implications of the observed TeV characteristics and show that it proves challenging to account for them within conventional acceleration and emission models. We discuss a new pulsar-type scenario for the origin of variable, very high energy (VHE) emission close to the central supermassive black hole and show that magneto-centrifugally accelerated electrons could efficiently Compton upscatter sub-mm ADAF disk photons to the TeV regime, leading to VHE characteristics close to the observed ones. This suggests, conversely, that VHE observations of highly under-luminous AGNs could provide an important diagnostic tool for probing the conditions prevalent in the inner accretion disk of these sources.

Comments: 5 pages, one figure (typos corrected); based on presentation at “High Energy Phenomena in Relativistic Outflows”, Dublin, Sept. 2007; accepted for publication in International Journal of Modern Physics D

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0805.4075v1 [astro-ph]

Submission history

From: Frank M. Rieger [view email]

[v1] Tue, 27 May 2008 09:08:36 GMT (23kb)

http://arxiv.org/abs/0805.4075

• ljk June 6, 2008, 0:15

MAGIC Observations of a 13-Day Flare Complex in M87 in February 2008

Authors: MAGIC Collaboration: J. Albert, et al

(Submitted on 5 Jun 2008)

Abstract: M87 is the only known non-blazar radio galaxy to emit very high energy (VHE) gamma-rays. During a monitoring program of M87, a rapid flare in VHE gamma-rays was detected by the MAGIC telescope in early 2008. The flux was found to be variable above 350 GeV on a timescale as short as 1 day on a significance level of $5.6\sigma$. The highest measured flux reached 15% of the Crab nebula flux.

We observed a rather complex flare structure with several substantial changes of the flux level during the 13-day observing period. The flux at lower energies (150 GeV to 350 GeV), instead, is compatible with being constant. The energy spectrum can be described by a power law with a photon index of $2.30 \pm 0.11_\mathrm{stat} \pm 0.20_\mathrm{syst}$.

The observed day-scale flux variability at VHE prefers the M87 core as source of the emission and implies that either the emission region is very compact (just few Schwarzschild radii) or the Doppler factor of the emitting blob is rather large in case of a non-expanding emission region.

Comments: 4 pages, 4 figures, submitted to ApJ letters

Subjects: Astrophysics (astro-ph)

Report number: MPP-2008-52

Cite as: arXiv:0806.0988v1 [astro-ph]

Submission history

From: Daniel Mazin [view email]

[v1] Thu, 5 Jun 2008 15:29:44 GMT (57kb)

http://arxiv.org/abs/0806.0988

• ljk April 27, 2009, 10:30

Variability Timescales in the M87 Jet: Signatures of E-Squared Losses, Discovery of a Quasi-period in HST-1, and the Site of TeV Flaring

Authors: D. E. Harris (SAO), C. C. Cheung (GSFC), Lukasz Stawarz (KIP/Stanford), J. A. Biretta (STScI), E. S. Perlman (FIT)

(Submitted on 24 Apr 2009)

Abstract: We investigate the variability timescales in the jet of M87 with two goals. The first is to use the rise times and decay times in the radio, ultraviolet and X-ray lightcurves of HST-1 to constrain the source size and the energy loss mechanisms affecting the relativistic electron distributions.

HST-1 is the first jet knot clearly resolved from the nuclear emission by Chandra and is the site of the huge flare of 2005. We find clear evidence for a frequency-dependent decrease in the synchrotron flux being consistent with E-squared energy losses. Assuming that this behavior is predominantly caused by synchrotron cooling, we estimate a value of 0.6 mG for the average magnetic field strength of the HST-1 emission region, a value consistent with previous estimates of the equipartition field.

In the process of analyzing the first derivative of the X-ray light curve of HST-1, we discovered a quasi-periodic oscillation which was most obvious in 2003 and 2004 prior to the major flare in 2005. The four cycles observed have a period of order 6 months.

The second goal is to search for evidence of differences between the X-ray variability timescales of HST-1 and the unresolved nuclear region (diameter <0.6″). These features, separated by more than 60 pc, are the two chief contenders for the origin of the TeV variable emissions observed by HESS in 2005 and by MAGIC and VERITAS in 2008.

The X-ray variability of the nucleus appears to be at least twice as rapid as that of the HST-1 knot. However, the shortest nuclear variability timescale we can measure from the Chandra data (<= 20 days) is still significantly longer than the shortest TeV variability of M87 reported by the HESS and MAGIC telescopes (1-2 days).

Comments: Accepted for publication in the Astrophysical Journal. 16 pages including 9 figures, some in color

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO); High Energy Astrophysical Phenomena (astro-ph.HE)

Cite as: arXiv:0904.3925v1 [astro-ph.CO]

Submission history

From: D. E. Harris [view email]

[v1] Fri, 24 Apr 2009 19:07:40 GMT (348kb)

http://arxiv.org/abs/0904.3925

• ljk September 14, 2009, 12:58

Discovery of CIV Emission Filaments in M87

Authors: W.B. Sparks, J.E. Pringle, M. Donahue, R. Carswell, M. Voit, M. Cracraft, R.G. Martin

(Submitted on 10 Sep 2009)

Abstract: Gas at intermediate temperature between the hot X-ray emitting coronal gas in galaxies at the centers of galaxy clusters, and the much cooler optical line emitting filaments, yields information on transport processes and plausible scenarios for the relationship between X-ray cool cores and other galactic phenomena such as mergers or the onset of an active galactic nucleus. Hitherto, detection of intermediate temperature gas has proven elusive.

Here, we present FUV imaging of the “low excitation” emission filaments of M87 and show strong evidence for the presence of CIV 1549 A emission which arises in gas at temperature ~10^5K co-located with Halpha+[NII] emission from cooler ~10^4K gas.

We infer that the hot and cool phases are in thermal communication, and show that quantitatively the emission strength is consistent with thermal conduction, which in turn may account for many of the observed characteristics of cool core galaxy clusters.

Comments: Accepted for publication in ApJ Letters

Subjects: Cosmology and Extragalactic Astrophysics (astro-ph.CO)

Cite as: arXiv:0909.2063v1 [astro-ph.CO]

Submission history

From: William B. Sparks [view email]

[v1] Thu, 10 Sep 2009 23:00:39 GMT (3328kb)

http://arxiv.org/abs/0909.2063