Ghostly Jets Haunt the Milky Way’s Black Hole

Article written: 30 May , 2012
Updated: 23 Dec , 2015


A ghost is haunting the Milky Way’s central black hole, revealing the galactic nucleus was likely much more active in the past than it is now. Scientists using the Fermi space telescope have found faint apparitions of what must have been powerful gamma-ray jets emanating from our galaxy’s center.

“These faint jets are a ghost or after-image of what existed a million years ago,” said Meng Su, an astronomer at the Harvard-Smithsonian Center for Astrophysics (CfA), and lead author of a new paper in the Astrophysical Journal. “They strengthen the case for an active galactic nucleus in the Milky Way’s relatively recent past.”

This is the first time this type of jet has been detected from the Milky Way’s black hole. Scientists know that other active galaxies have cores that glow brightly, powered by supermassive black holes swallowing material, and often spit twin jets in opposite directions.

The two beams, or jets found by Fermi observations extend from the galactic center to a distance of 27,000 light-years above and below the galactic plane.
The newfound jets may be related to mysterious gamma-ray bubbles that Fermi detected in 2010. Those bubbles also stretch 27,000 light-years from the center of the Milky Way. However, where the bubbles are perpendicular to the galactic plane, the gamma-ray jets are tilted at an angle of 15 degrees. This may reflect a tilt of the accretion disk surrounding the supermassive black hole.

“The central accretion disk can warp as it spirals in toward the black hole, under the influence of the black hole’s spin,” explained co-author Douglas Finkbeiner of the CfA. “The magnetic field embedded in the disk therefore accelerates the jet material along the spin axis of the black hole, which may not be aligned with the Milky Way.”

The two structures also formed differently. The jets were produced when plasma squirted out from the galactic center, following a corkscrew-like magnetic field that kept it tightly focused. The gamma-ray bubbles likely were created by a “wind” of hot matter blowing outward from the black hole’s accretion disk. As a result, they are much broader than the narrow jets.

Both the jets and bubbles are powered by inverse Compton scattering. In that process, electrons moving near the speed of light collide with low-energy light, such as radio or infrared photons. The collision increases the energy of the photons into the gamma-ray part of the electromagnetic spectrum.

The discovery leaves open the question of when the Milky Way was last active. A minimum age can be calculated by dividing the jet’s 27,000-light-year length by its approximate speed. However, it may have persisted for much longer.

“These jets probably flickered on and off as the supermassive black hole alternately gulped and sipped material,” said Finkbeiner.

It would take a tremendous influx of matter for the galactic core to fire up again. Finkbeiner estimates that a molecular cloud weighing about 10,000 times as much as the Sun would be required.

“Shoving 10,000 suns into the black hole at once would do the trick. Black holes are messy eaters, so some of that material would spew out and power the jets,” he said.

Source: CfA

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19 Responses

  1. Julien Redmond says

    so if the jets are only out 27000 light years docent that mean that they happened 27000 years ago?

    • Ionut Dumitrascu says

      No, because the jets did not “travel” at the speed of light. That’s why it’s said in the article: “A minimum age can be calculated by dividing the jet’s 27,000-light-year length by its approximate speed”.
      As to what that approximate speed is…..:) I’ll leave it to someone more qualified to answer that.

      • newSteveZodiac says

        Not very qualified but red/blue shift would tell you the speed of the jets, approximately because they are not moving directly towards or away.

      • the_only_fan says

        you have take into account the forming time of the beam and the distance from the earth to the galactic center. you will arrive to quite some time

  2. MichaelWSimmons says

    Would these jets have been visible when they where active?
    Would they have affected life on earth in anyway?

    • Jon Souter says

      > Would they have affected life on earth in anyway?

      Only if the angle of the jets varied so much that they pointed directly in our direction.

      As to what the effect of that would be at our distance from the galactic centre… that’s best answered by someone with a deeper understanding of the physics involved.

  3. Ummm… can you say Electric Universe?!?!

    • DrFlimmer says

      No, you can’t. 😉

    • Jon Souter says

      From the little I understand about Electric Universe / Plasma theory – the notion of black holes is not accepted.

      What electric phenomena are likely to be causing the jets we see all over the visible universe?

      • Really20 says

        TEU is merely another absurd “theory,” made by people who think that currently accepted astrophysics is based on “just” theories.

    • Olaf2 says

      Can’t since black holes in EU is blasphemy!

  4. Ignoramus1 says

    “Both the jets and bubbles are powered by inverse Compton scattering”
    Is that a fact?

    • DrFlimmer says

      It’s at least very likely, since high energetic electrons tend to upscatter “soft” radiation rather efficiently to gamma rays. And electrons that are shot out from the vicinity of a super massive black hole usually have VERY high energies.

  5. Olaf2 says

    Why are the jets not a spiral?

  6. lcrowell says

    As a point of physics, the jet executes a cork screw motion because of angular momentum coupling between the black hole + accretion disk with the rest of the galaxy. If the angular momentum of the Bh+accretion disk is J and that of the rest of the galaxy is J’, then the inner product between these two angular momentum vectors J•J’ defines a part of the Hamiltonian of the system which pertains to angular momentum

    H = (1/2)(J^2 + J’^2) + c J•J’

    The Hamiltonian is the “energy function.” Here c is a coupling constant, which is a bit complicated and not as relevant and the inner product of the two angular momentum vectors is equal to their magnitudes times the cosine of the angle between them J•J’ = |J||J’|cos(?).

    Assume we want to calculate the rate the accretion disk angular momentum changes or precesses. We want to calculate the time derivative of J ?J/?t. Now for those familiar with Hamiltonian mechanics you know that ?J/?t = -?H/??, where the azimuthal angle is the rotation angle in the plane perpendicular to J. How do we calculate this? The only thing in the Hamiltonian that has angular dependency is c|J||J’|cos(?). The angle ? is the difference between the azimuthal angle for J and J’, or ? = ? – ?’. So write the relevant part of the Hamiltonian as c|J||J’|cos(? – ?’). I leave the rest to the interested reader. Use some angle addition or subtraction formulas in trigonometry and calculate the easy derivative with respect to ?. This is a way one can see how the accretion disk + black hole precesses. This causes the jet to have a cork screw shape as it leaves the galaxy over time.



    Well, this is somewhat belated, but better late than never…

    Here are links to two relevant papers:

    Evidence for Gamma-ray Jets in the Milky Way;

    Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?

  8. TomN says

    Would these jets and the bubble have an effect on the formation and life cycle of globular clusters (like M13) that may inhabit that region around the core?

  9. TomN says

    Would these jets and the bubble have an effect on the formation and life cycle of globular clusters (like M13) that may inhabit that region around the core?

  10. dovhenis says

    Another look at the universe?

    Natural Selection Is Ubiquitous

    Higgs Particle? Dark Energy/Matter? Epigenetics?
    These Are YOK!
    Update Concepts-Comprehension…

    Evolution Is The Quantum Mechanics Of Natural Selection.
    The quantum mechanics of every process is its evolution.
    Quantum mechanics are mechanisms, possible or probable or actual mechanisms of natural selection.

    Universe-Energy-Mass-Life Compilation

    A. The Universe

    From the Big-Bang it is a rationally commonsensical conjecture that the gravitons, the smallest base primal particles of the universe, must be both mass and energy, i.e. inert mass yet in motion even at the briefest fraction of a second of the pre Big Bang singularity. This is rationally commonsensical since otherwise the Big would not have Banged, the superposition of mass and energy would not have been resolved.

    The universe originates, derives and evolves from this energy-mass dualism which is possible and probable due to the small size of the gravitons.

    Since gravitation Is the propensity of energy reconversion to mass and energy is mass in motion, gravity is the force exerted between mass formats.

    All the matter of the universe is a progeny of the gravitons evolutions, of the natural selection of mass, of some of the mass formats attaining temporary augmented energy constraint in their successive generations, with energy drained from other mass formats, to temporarily postpone, survive, the reversion of their own constitutional mass to the pool of cosmic energy fueling the galactic clusters expansion set in motion by the Big Bang.

    B. Earth Life

    Earth Life is just another mass format. A self-replicating mass format. Self-replication is its mode of evolution, natural selection. Its smallest base primal units are the RNAs genes.

    The genesis of RNAs genes, life’s primal organisms, is rationally commonsensical thus highly probable, the “naturally-selected” RNA nucleotides.

    Life began/evolved on Earth with the natural selection of inanimate RNA, then of some RNA nucleotides, then arriving at the ultimate mode of natural selection, self-replication.

    C. Know Thyself. Life Is Simpler Than We Are Told, Including Origin And Nature Of Brain And Of “Spirituality”***

    The origin-reason and the purpose-fate of life are mechanistic, ethically and practically valueless. Life is the cheapest commodity on Earth.

    As Life is just another mass format, due to the oneness of the universe it is commonsensical that natural selection is ubiquitous for ALL mass formats and that life, self-replication, is its extension. And it is commonsensical, too, that evolutions, broken symmetry scenarios, are ubiquitous in all processes in all disciplines and that these evolutions are the “quantum mechanics” of the processes.

    Human life is just one of many nature’s routes for the natural survival of RNAs, the base primal Earth organisms.

    Life’s evolution, self-replication:

    Genes (organisms) to genomes (organisms) to mono-cellular to multicellular organisms:

    Individual mono-cells to cooperative mono-cells communities, “cultures”.

    Mono-cells cultures evolve their communication, neural systems, then further evolving nerved multicellular organisms.

    Human life is just one of many nature’s routes for the natural survival of RNAs, the base Earth organism.

    It is up to humans themselves to elect the purpose and format of their life as individuals and as group-members.

    Dov Henis (comments from 22nd century)

    ***????? ?????? ?? “?????????”, ???? ??????????,
    ?????????? ?????? ?????????, ?????? ??????? ????

    An Embarrassingly Obvious Theory Of Everything

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