At the center of our galaxy is a sleeping giant, a black hole more than four million times as massive as the sun. The Milky Way’s supermassive black hole is mostly quiet, nibbling on small objects at the galactic center and giving off only faint belches of radiation as it digests its prey. But in the past the sleeping giant may have been wide awake—and wreaking havoc.

Astrophysicists at the Harvard–Smithsonian Center for Astrophysics have uncovered evidence of two ghostly but enormous beams of gamma rays, each extending some 30,000 light-years from the galactic center, that seem to mark a violent episode of black hole consumption relatively recently in cosmic history.

Supermassive black holes in some other galaxies are much more active than Sagittarius A* (Sgr A*), the lurker at the center of the Milky Way. As black holes devour gas, dust or even fully formed stars, matter compresses and heats up in an accretion disk outside the event horizon, a black hole's point of no return. That messy accretion process can produce copious radiation or outflows of plasma. As a result, feeding black holes can glow brightly, even across billions of light-years, and some emit giant jets of particles that extend away from the black hole. But such jets had not been identified near our own, mostly dormant, supermassive black hole.

The jets appear as faint lines in maps of the galaxy made by NASA's Fermi Gamma-Ray Space Telescope. Harvard graduate student Meng Su and astrophysicist Douglas Finkbeiner identified the feature by subtracting known gamma-ray sources from Fermi's maps and teasing out the patterns in the diffuse emission left behind. Their finding appears in a study to be published in The Astrophysical Journal. The jets have not been detected at other wavelengths or with other telescopes, but next-generation x-ray space telescopes may be able to confirm or refute their existence.

If the jets emanating from Sgr A* prove to be real features and not just a trick of the eye, they would indicate that, not so long ago, the black hole was much feistier than it is now. One explanation for the jets is that during a feeding-driven outburst, material was funneled outward from the black hole along narrow, oppositely directed jets constrained by a corkscrewing magnetic field. High-energy electrons rushing along those jets collided with background photons, boosting them up to gamma-ray energies, which Fermi's Large Area Telescope can detect.

But just when the jets would have been produced is not simple to pin down—the gamma rays now reaching telescopes could be relics of a whole series of outbursts. Indeed, the hypothesized jets are not the first piece of indirect evidence that Sgr A* gorges itself from time to time. Radiation bouncing off of molecular clouds in the galaxy has been interpreted as an echo of earlier outbursts just hundreds of years ago. "We know that even on a few-century timescale the black hole flickers on and off," Finkbeiner says.

The newfound jets may be related to another feature that Su and Finkbeiner, along with their colleague Tracy Slatyer, now at the Institute for Advanced Study, recently spotted extending from the galactic center. In 2010 the researchers, again using the Fermi telescope, identified huge bubbles above and below the plane of the Milky Way, glowing with gamma rays. The bubbles could also have been produced by energetic electrons, ejected during a black hole feeding frenzy, colliding with mundane photons and raising them up to gamma-ray energies. The so-called Fermi bubbles and the jets may stem from the same outburst a million or so years ago—the jets would be the high-velocity black-hole output, and the bubbles the decelerated material spreading outward in a series of shocks and eddies. But whereas the jets and bubbles overlap in location and scale, the jets are tilted by about 15 degrees, and the researchers note that they could result from separate episodes.

10 Comments

1. 1. newman 07:59 AM 6/1/12

   The universe are in change.
   The black holes are ine big mysterius!
   If someone read the Stephen Hawking theorys about this. I think this holes have one type of magnetic energy who "eat, eat, eat" the lights, of anorthers stars, planets.
   I say this because this old stars when your life is in the end, she explod and have one type energy who the light or the more fast light cannot escape.
   In our galaxie maybe have one black hole like this. Someone have doubs?
   Unfortunately our technology is obsolete.
   
   
   

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2. 2. jtdwyer 08:33 AM 6/1/12

   The article states:
   "The so-called Fermi bubbles and the jets may stem from the same outburst a million or so years ago—the jets would be the high-velocity black-hole output, and the bubbles the decelerated material spreading outward in a series of shocks and eddies. But whereas the jets and bubbles overlap in location and scale, the jets are tilted by about 15 degrees, and the researchers note that they could result from separate episodes."
   
   I suggest that, more likely, the position of the bubbles is determined by the magnetic or gravitational polar orientation of the energized free electrons to the galaxy's disk, whereas the positions of trace gamma rays once produced by active relativistic jets is determined by the position of the supermassive black hole's magnetic field directing the jets.
   
   In this case, free electrons stripped from matter accelerated by its accretion towards the SMBH (somewhat similarly to electrons being stripped away from nucleons during the collapse of a neutron star) were initially ejected but were captured by the galaxy's magnetic and/or gravitational fields. The bubbles of free electrons were excited by the then AGN's relativistic jets emitting elementary particle residue produced by the continued decomposition of nucleons, somewhat similar to the conditions produced by the LHC except their elementary particle residue is not localized by head-on collision, producing immediate decay: it continues at relativistic velocities, producing a long lived stream of high energy fundamental particles.
   
   This decomposition of matter could allow the local retention of its singularly directed gravitational energy without retaining the spatial occupancy required by its now ejected dimensional particles. In this way an effective gravitational singularity could be produced without requiring any spatial occupancy for local storage of dimensional matter.

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3. 3. lamorpa in reply to newman 10:47 AM 6/1/12

   newman:
   Is the title of your poem, 'Ode to all back hole in galaxie'? It's quite interesting. I feel that while the rhythm and meter varies, this narrative progresses through its stanzas with definite enjambment. Minimal use of clichés, metaphor and personification enhance the realism of this blank verse.

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4. 4. rloldershaw 10:58 AM 6/1/12

   
   Many astrophysical systems have highly collimated back-to-back jets emanating from their cores. For example, gamma-ray burst sources, pulsars, Haro-Herbig systems, black holes, quasars, BL Lac galaxies, radio galaxies, Seyfert galaxies, elliptical galaxies and spiral galaxies.
   
   In most well-observed cases the jets are generated by an ultracompact and highly relativistic core object, most often a black hole.
   
   How then do we understand the jets observed in supernovae, brown dwarf stars, proto-stars, and young stellar objects? Is it possible that ultracompact "nuclei" lurk semi-anonymously in these systems too? Might not all major classes of stellar and galactic systems be nucleated by ultracompact relativistic "nuclei"?
   
   Since this is the case with atomic scale systems, Discrete Scale Relativity predicts that it is also true for stellar and galactic scale systems.
   
   Robert L. Oldershaw
   http://www3.amherst.edu/~rloldershaw
   Discrete Scale Relativity
   Fractal Cosmology
   

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5. 5. jtdwyer in reply to rloldershaw 07:24 PM 6/1/12

   Are you seriously suggesting the existence of atomic
   scale accretion disks and relativistic jets? What would
   they be?

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6. 6. newman in reply to lamorpa 08:51 AM 6/4/12

   I'm not a poet, perhaps a visionary.
   I see black holes as a great mystery of the universe.
   They contain a kind of energy that devours everything.
   In our galaxy there is evidence that small black holes.
   Nobody knows, nobody study because we do not have enough technology to study it.
   Because of this there is so much fantasy in it. Read Stephen Hawking and his theory of wormholes (black holes).
   My colleagues share the same opinion.
   Goodbye.

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7. 7. lamorpa in reply to newman 09:04 AM 6/4/12

   I do agree
   With the mystery
   Of beautiful black holes
   Matter and energy
   Devoured
   

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8. 8. Richard2161 10:13 PM 6/4/12

   I would have enjoyed Matson's piece more if he had stayed away from mythopoetic/anthropomorphic nonsense about sleeping giants awaking and devouring stuff, etc. (the metaphor "black hole" is bad enough)
   
   Surely the universe is sufficiently amazing without "improving" on it with feeble human projections.

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9. 9. AmericanTreasure 03:59 PM 6/7/12

   What if we can pinpoint changes within DNA (for example, 'substitutions, deletes, and insertions'), with chronologically confirmed galactic events?

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10. 10. Quinn the Eskimo 09:34 PM 6/17/12

    Maybe these jet-plumes happened on Galactic Garbage Day and the truck ain't been by yet?

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