Fermi Telescope Finds Giant Structure in the Milky Way


From a NASA press release:

NASA’s Fermi Gamma-ray Space Telescope has unveiled a previously unseen structure centered in the Milky Way. The feature spans 50,000 light-years and may be the remnant of an eruption from a supersized black hole at the center of our galaxy.

“What we see are two gamma-ray-emitting bubbles that extend 25,000 light-years north and south of the galactic center,” said Doug Finkbeiner, an astronomer at the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., who first recognized the feature. “We don’t fully understand their nature or origin.”

The structure spans more than half of the visible sky, from the constellation Virgo to the constellation Grus, and it may be millions of years old. A paper about the findings has been accepted for publication in The Astrophysical Journal.

Finkbeiner and Harvard graduate students Meng Su and Tracy Slatyer discovered the bubbles by processing publicly available data from Fermi’s Large Area Telescope (LAT). The LAT is the most sensitive and highest-resolution gamma-ray detector ever launched. Gamma rays are the highest-energy form of light.

Other astronomers studying gamma rays hadn’t detected the bubbles partly because of a fog of gamma rays that appears throughout the sky. The fog happens when particles moving near the speed of light interact with light and interstellar gas in the Milky Way. The LAT team constantly refines models to uncover new gamma-ray sources obscured by this so-called diffuse emission. By using various estimates of the fog, Finkbeiner and his colleagues were able to isolate it from the LAT data and unveil the giant bubbles.

Scientists now are conducting more analyses to better understand how the never-before-seen structure was formed. The bubble emissions are much more energetic than the gamma-ray fog seen elsewhere in the Milky Way. The bubbles also appear to have well-defined edges. The structure’s shape and emissions suggest it was formed as a result of a large and relatively rapid energy release — the source of which remains a mystery.

One possibility includes a particle jet from the supermassive black hole at the galactic center. In many other galaxies, astronomers see fast particle jets powered by matter falling toward a central black hole. While there is no evidence the Milky Way’s black hole has such a jet today, it may have in the past. The bubbles also may have formed as a result of gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way’s center several million years ago.

“In other galaxies, we see that starbursts can drive enormous gas outflows,” said David Spergel, a scientist at Princeton University in New Jersey. “Whatever the energy source behind these huge bubbles may be, it is connected to many deep questions in astrophysics.”

Hints of the bubbles appear in earlier spacecraft data. X-ray observations from the German-led Roentgen Satellite suggested subtle evidence for bubble edges close to the galactic center, or in the same orientation as the Milky Way. NASA’s Wilkinson Microwave Anisotropy Probe detected an excess of radio signals at the position of the gamma-ray bubbles.

The Fermi LAT team also revealed Tuesday the instrument’s best picture of the gamma-ray sky, the result of two years of data collection.

“Fermi scans the entire sky every three hours, and as the mission continues and our exposure deepens, we see the extreme universe in progressively greater detail,” said Julie McEnery, Fermi project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md.
NASA’s Fermi is an astrophysics and particle physics partnership, developed in collaboration with the U.S. Department of Energy, with important contributions from academic institutions and partners in France, Germany, Italy, Japan, Sweden and the United States.

“Since its launch in June 2008, Fermi repeatedly has proven itself to be a frontier facility, giving us new insights ranging from the nature of space-time to the first observations of a gamma-ray nova,” said Jon Morse, Astrophysics Division director at NASA Headquarters in Washington. “These latest discoveries continue to demonstrate Fermi’s outstanding performance.”

27 Replies to “Fermi Telescope Finds Giant Structure in the Milky Way”

  1. Proving once again:
    There is no substitute for the accurate collection of data !!!
    Bravo Fermi !!!

    But now we have as our foible, the correct interpretation of that data !

  2. The orientation of these bubbles along the galacic poles and centered as they are I think unmistakably points the finger at the SMBH as the source. Finding evidence for large gamma ray outbursts should not be too surprising, considering evidence from quasars both near and far. Eventually we should learn the kinds of things the SMBH snacks upon and what types of outbursts they produce from observations of active galactic nuclei that are relatively nearby. I have speculated that perhaps a pulsar or large star being ripped apart as it wanders too close to the SMBH could produce such an outburst.

  3. This is interesting news, which is welcome from an astrophysics perspective, but troublesome from a particle physics perspective. However, maybe this replaces problematic particle physics data with astrophysics data. My sense of course is that these lobes are the remnants of galactic jets or activity in the galaxy center produced by a black hole. The Milky Way galaxy has a modest SMBH that weighs in at 10 million solar masses.

    Over the past month, science news sites and blogs have been abuzz over a possible sighting of dark matter, based on a paper by Fermilab’s Dan Hooper and NYU’s Lisa Goodenough. This time, the reports say, a number of cosmologists (Michael Turner) have found these data to be the “ most compelling evidence of dark matter particles to date.” These data are odd in a way. The observed spectra has a peak in the 2-4 GeV region predicted for a weakly interacting dark matter particle with mass 7.3-9.2 GeV that annihilates into tau leptons. The cross sections are in the range more or less expected ~ 10^{-37}cm^2. This is problematic for these putative DM particles are light, they are particles which should have been found in particle experiments a long time ago. A DM particle that decays into tau tau-bar pair is plain strange as I see it. This might suggest new physics though, for maybe the DM particle, say the neutralino that weighs in at around 1 TeV might decay into a condensate, or a plasma (glasma) that decays into a “gas” of tau tau-bar pairs (tau lepton plus its anti-particle).

    I might attempt to propose a toy model consider a five dimensional “spacetime plus R” space. This fifth dimension is a space with a gauge connection or potential U which defines a force F = -dU/dx_5, for x_5 a parameter on this fifth dimension. To make this even simpler the potential might just be U = -gx_5, similar to simple gravity near Earth and the force. For the fifth dimension a simple interval [0, L] the black hole case is x = L and the quasi-black hole or QCD plasma is at x = 0. So the “black hole” at the top for particle masses m ~ 0 has this continual flow to heavy masses at the bottom. This might connect with Zamolodchickov’s s = -1/2 massive conformal theory. So maybe there is some duality on these boundaries between a BPS black hole and a plasma-condensate of particles. So the duality between spacetime isometries on these boundaries and conformal symmetries, such as the massive conformal symmetry which might exist on x = 0.

    I propose this model above as something to chew over, not as something I am trying to monger here. This plasma condensate I would expect to be composed of quarks and gluons, which I would expect then to decay into low energy mesons. The paper arXiv:1010.2752 by Goodenough and Hooper do analyse these processes. It is odd though that this would decay into tau tau-bar. This might suggest the quarks in the glasma are top and bottom quarks, if there is some connection between the lepton and quark sectors here. It is all very mysterious IMO, but intriguing.

    In looking at the above paper with some closeness and this more informal press release I am interested to what degree these data are completely decoupled from each other. If the presumed DM results above are not induced by data involved with this lobe, then physicists will have to take seriously the prospect that DM particles decay by leptonic channels, and signatures of these need to be filtered through in LHC data.


  4. Great!
    I love to know:
    1 how faint is that gamma-ray bubble? only be seen until today
    2 Do you mean more and more dark matter turning to the “bright side”?
    how fast is the turning rate.
    3 Do they have radio or UV counterparts ?

  5. How long will dark matter last? That is an interesting question. I will attempt to calculate an estimate for that. The volume of a galactic halo is about 10^{18} cubic light years or 10^{66}m^3. The mass of DM in a galaxy is about 10^{11} solar masses or 10^{41}kg. Therefore the density is 10^{-24}kg/m^3 over all. However, for the central region of a galaxy this density may be about 100 times that, so each cubic meter has maybe 10^{-22}kg of DM. Now a proton has a mass of about 10^{-27}kg and a DM particle we might estimate has about 100 protons of mass. So a cubic meter of space might have 1000 DM particles in it.

    Now this matter is cold or about 100K. We use this in the Boltzmann equation. So in a cubic meter of space there are N ~ 1000 particles and the kinetic energy of them is E = Nmv^2/2 — Newtonian physics works at these low temperatures and energy. The Boltzmann constant times the temperature kT gives the E/kT that enters into the Boltzmann factor Z ~ exp(-E/kT). This gives a probability dP = ZdE/kT and Z = int dP. We may then find the mean free path is approximately

    = int xdP ~ kT/(rho*A*L)

    where rho is the density, L is the volume length for N particles, and A is the cross section for these particles which is about 10^{-36}m^2. So now turn the crank and we get ~ 1.38066×10^{?23} J/K * 100K/10^{-24}*10^{-28} ~ 10^{31}m. That is a long mean free path! That is more distant than to the CMB.

    We use the equipartition theorem E ~ 3kT/2 to estimate the energy Nmv^2/2 and we get the velocity v = sqrt{kT/3Nm} ~ 100m/s — again an estimate. So each particle will travel it mean free path in 10^{29}seconds. That is a long — a very long time. However, there are a lot of these particles. The DM mass is on average 10^{41}kg or consists of about 10^{66} of these particles. About 1/100th of this is near the center of galaxy and accounts for about 100 times the density, so maybe about 10^{40} of these particles are being annihilated every second, or about a trillion kg/sec or an net energy output of about 10^{29}watts of power output. This is about 1000 times the power output of the sun, but it must be remembered this is in gamma rays and not optical radiation as with the sun.

    The time it takes the DM to decay to half it current quantity is about 10^{29} seconds, or 10^{22} years. All of these estimates might be off by a couple of orders of magnitude, but this rough estimate captures approximately what things should turn out under more rigorous analysis. The stellar phase of the galaxy will end in about 10^{13} years, so DM will be around in abundant quantity to hold the galaxy together long enough. I would presume that after 10^{23} years or so when DM has largely decayed away that most matter not bound in the SMBH at the center will then drift away.


  6. We better watch these G-ray bubbles closely, the rate of growed will be
    important as well as the time frame, it is a sign of what comes next.
    It may develop into jets or it will burst, in each case it will cause trouble for us!
    I was expecting a light dome but we are already past that, this is not about what
    happen in the past but what is to come! It took only two centuries to grow to its
    present size and that is fast in universal time.

  7. The image is an illustration.

    Find the real data here:

    I have to wonder if the jets are part of a galaxy’s interstellar gas accretion mechanism.

    As noted in this Post:

    I expect that the energy jets would follow field lines across the galactic sheath. Much as field lines in a magnet might. ? Or or solar Helio-sheath.

    Where they interact with the intergalactic medium gamma rays are generated?

  8. Our scientists still do not recognize one important thing: All the matter that exists in this galaxy (except for later captured one) came OUT of the black hole at the galactic center.

    When galaxies start forming, the jets are visible and they have active nucleus – the black hole is spewing out matter which then becomes stars and planets (Centaurus A).

    Later, the jets subside and the energy coming out of the black hole is reduced. What they’ve just discovered are the traces of energy coming OUT of the black hole. Energy that sustains this galaxy and keeps this galaxy in one piece.

  9. Catamarion: I just can’t let this go by. Black holes are gravitational wells which are so intense that spacetime is curved at some length smaller than a critical radius so as to be removed from the universe. As it is said, black holes are black because light is unable to escape. There is nothing which can escape a black hole in a causal manner. Black holes do quantum mechanically radiation matter out, but for a black hole larger than the mass of the sun this is negligible.

    Jets do not emerge from a black hole, but are due to plasma physics of material outside a black hole.


  10. @Catamarion
    The jets are not coming from inside the black hole. The jets is the mass outside the black-hole getting accelerated by magnetic fields of the black hole and ejected upwards and downwards. This mass never got in a black hole.

    thank you very much. though I can hardly follow your calculations. I just don’t know how do explain the shape of that 2 blobs via DM.
    They looks more like a remnant of jets for a glance. I know remnants of supernova prefer high-energy band too. Accelerated by shocks
    I thought you may calculate the annihilation rate through the total gamma flux of the FERMI discovery.

  12. I brought up the DM because the FERMI Gamma rays telescope spacecraft has found signatures of DM decay by leptonic channels. The leptonic decay channel in the 10 GeV energy range is to me surprising. The question I have is to what degree these data interpreted as galactic activity, presumably due to a SMBH and past jet activity, and DM decays have been separated from each other. The two data sets need to be filtered appropriately. This data was recently reported by Hooper and Goodenough last month.

    The two lobes pictured here have features I might expect from galactic activity. This might reflect some MeV particles or photons leaving the region near the galaxy core which then irradiate diffuse atoms, which then re-radiate as gamma and X-ray photons. If this activity were increased considerably it might manifest itself as a galactic jet, and our galaxy has undoubtedly had such during episodes in the past. So I would tend to say these lobes are likely to be predominantly due to galactic activity.


  13. OK, they are not coming directly FROM the black hole. I agree.

    But what if a black hole is a downstepper of incoming energy from higher dimensions? We would not see it if it existed in (say) 5th-7th dimension only, serving as a portal downstepping the energy to our 4D time-space universe.

    It really does not matter whether the energy comes from the black hole or appears as a ring near to the black hole, wherefrom it is then ejected to the space.

    Stop looking at a black hole as a devourer. What if it is an energy giver?

    If the matter in this whole universe once came out of a singularity (so-called Big Bang), why wouldn’t be possible that the matter in this galaxy came also from a singlarity at the center of the Milky Way?

    Think out of the box.

  14. Let me explain my reasoning.

    Let’s say we existed as 2D creatures, in which case our galaxy would be a 2D object drawn on a large sheet of paper. Let’s say that those 2D creatures living in that flat galaxy would start pondering wherefrom all that ink is coming that is used to draw this huge galaxy.

    Now imagine a 3D ink pen placed perpendicularly to 2D galaxy with the tip touching the paper at the center of that galaxy and actually bleeding the ink.

    How would those 2D creatures see it? To them, the ink would be coming out of nowhere to their 2D reality. For them, it would be a miracle.

    And what if that is the case with the black hole at the center of our galaxy? What if a higher dimensional structure exists there and touches our 4D reality at that very point. And what if it is bleeding energy?

    Wouldn’t we be seeing what we are in fact seeing? Namely, nothing spewing out matter in jets?

    Funny thing being, we could actually take the superstring theory and create a hypothetical model that would fit the description and actually work – perfectly explaining the galactic physics.

  15. @Catamarion, logical reasoning does not mean it is true in reality.
    You create an idea and then try to find a story around it to fit your idea.

  16. To OLAF:

    And our science does exactly the same. Or do you have any idea how our galaxy works?

    Can you tell me why is it that our sun revolves around the galactic center with same angular velocity like other stars located closer to the center?

    How do you explain this flat disk rotation? What laws describe it?

    The truth is: We have no idea. No formulas to explain the phenomenon.

    Should somebody come with a superstring theory finetuned to what we see, it would be our science’s best shot. The best thing we have to describe the galactic physics.

  17. Catamarion,

    Black holes do have connections with higher dimensions, such as N1-N5-branes, BPS gauge charged black holes, moduli space for multi-partite entangled black hole states on coset groups of Q-bits and … . However, this subject is way beyond the scope of any blog post here. The upshot is still the same. A black hole is a quantum system, which emits quanta if it is very small — a quantum black hole. For large black holes there is a transition to classical behavior. A stellar size and even more a galactic SMBH is black, it emits essentially no energy. A stellar mass black hole will take 10^{67} years to quantum decay and a 10^{8} solar mass SMBH will take about 10^{100} years to decay. Further, they only decay once the background is at a lower temperature than the horizon temperature. Those conditions will not set in for another 10^{50} years or so.


  18. Wow! Who ordered that? I agree with Olaf on hourglass if steady state phenomena from BH, and the post discuss it as transient I believe. Elsewhere I see that star burst and transient SMBH jets are combined as hypothesis.

    How do you explain this flat disk rotation? What laws describe it? The truth is: We have no idea. No formulas to explain the phenomenon.

    We do have the MOND formulas. The idea AFAIU though is that DM explains it, as it predicts something generally similar that fits best everywhere else and makes a necessary part of the standard cosmology.

    I’m not sure why you start handwaving on everything but the discussed phenomena, but as a rule it has never elevated anyone to any knowledge ever. To fly you need science.

  19. The galaxy does of course have a gravity field, which is larger than what could be accounted for with luminous matter. There is also a magnetic field, which FAPP at low energy has nothing to do with gravity. I say FAPP for there is unification of gravity and electromagnetism at high energy, but that is not very relevant here. The magnetic field has a very small field, about a billionth of a Gauss. Of course it is large and extends over a 100,000 light years. There is also a magnetic dynamo action which occurs with the plasma around the central black hole, where there field strengths can be very large, but more local.


  20. Whatever it is, I think that the whole thing is stable, being continuously generated by the black hole at the galactic center.

    It is not a remnant of anything. It is kind of a field holding this galaxy.

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