DOUBLE BUBBLE: An artist's conception showing the approximate scale of the newfound Fermi bubbles above and below the Milky Way.
Image: NASA/GSFC
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A group of astrophysicists has located two massive bubbles of plasma, each extending tens of thousands of light-years, emitting high-energy radiation above and below the plane of the galaxy. The researchers found the structures in publicly released data from NASA's Fermi Gamma-Ray Space Telescope, which was launched in 2008 to investigate sources of extremely energetic photons—namely, gamma rays, which have higher frequencies than x-rays.
From its orbital perch hundreds of kilometers above Earth's surface, Fermi has charted the location of gamma-ray sources with its Large Area Telescope (LAT). But just where the gamma rays originate is not always clear; the foreground of Fermi's view is clouded with emission from events such as cosmic rays striking dust in the Milky Way's disk. To get a better picture of the gamma-ray environment, Douglas Finkbeiner of the Harvard–Smithsonian Center for Astrophysics and his colleagues carefully subtracted those sources based on maps showing locations of cosmic dust, models of the galactic disk, and known emitters of gamma rays, such as active black holes in other galaxies.
"There are many kinds of emission in the Fermi maps—there are things that we're expecting to see, like the dust-correlated emission," Finkbeiner said in an interview during the May meeting of the American Astronomical Society. Finkbeiner presented at the conference an early version of the research, which has now been finalized and readied for publication. "But then we saw some other things that we weren't expecting," Finkbeiner said in the interview. "We saw these giant bubbles reaching above and below the galactic center." The study, co-authored with graduate students Meng Su and Tracy Slatyer, will appear in The Astrophysical Journal. (Slatyer is now at the Institute for Advanced Study in Princeton, N.J.)
Finkbeiner compared the shape of the lobes of the so-called Fermi bubbles with teardrops or hot-air balloons. The two bubbles are symmetric, and each appears to originate at the Milky Way's center, where a black hole with the mass of four million suns lurks. Together they span a distance roughly half the diameter of the Milky Way. The origin of the Fermi bubbles is unknown, but a population of high-energy electrons that collides with mundane photons, boosting them to gamma-ray energies, seems to be the cause. Matter falling onto the galaxy's central black hole could give off a good deal of energy to produce electrons swept up in a hot plasma—and ultimately the gamma rays.
"When stuff falls into that black hole, as you can imagine, it makes a big mess," Finkbeiner said. "One of the things that happens is very high-energy particles get ejected, and probably shock waves, and you can get jets of material coming off of the thing." Those jets could blast into the interstellar medium above and below the plane of the galaxy and form bubbles that emit gamma rays.
An alternate possibility is a relatively recent burst of star formation in the inner galaxy, probably within the last 10 million years. "If you have many young stars all forming in the same place at the same time, they have tremendous stellar winds; some of them will blow up as supernovae—a lot of things can happen that heat gas and cause bubbles to expand," Finkbeiner said.
The researchers found flaws with both proposed explanations but noted that some combination of the two could be the cause. And indeed, David Spergel, a Princeton University astrophysicist who did not contribute to the study, explains that black hole accretion and starbursts can be related. "What we see in some external galaxies is the same inflow onto a black hole also produces a burst of star formation," Spergel says.
Spergel notes that much astrophysical work focuses on filtering out the foreground of Milky Way structures to see into the distant universe. "For most cosmologists our galaxy is an enormous nuisance," he says. "This is one of those instances where one scientist's foreground and garbage is another scientist's field of study."
Scooping new discoveries from a mission's public data sometimes causes disagreements of interpretation between the independent data miners and the mission's own scientists. To wit, Finkbeiner's 2003 detection of a haze of excess microwave emission near the galactic center in data from the Wilkinson Microwave Anisotropy Probe (WMAP) has not been fully accepted by Spergel and other members of the WMAP team.
But the Fermi team appears to be on board with the new finding. "Our view of this work is that this is an important discovery," offers Stanford University astrophysicist Peter Michelson, the principal investigator for Fermi's LAT. "Doug's work is excellent." Michelson adds that the study highlights the importance of involving a wider community of scientists through public data releases and notes that the mission team is working on its own follow-up analysis. "There remains much interesting work to do to figure out the real origin of these incredible bubbles in our galaxy," Michelson says.
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16 Comments
Add CommentIt seems to me that either the data is flawed or the artist's conception is wrong or someone has misspoken; these 'bubbles' can't possibly be recent, having expanded that far they've been around a long time, and we're not stuck in place in the universe, we're zipping right along at many miles per second. Speeds like that spread out over that many years at those distances would have to apply a significant distortion to any 'bubble'; something's out of whack.
Reply | Report Abuse | Link to this@promytius - Haha! You're funny... had me going for a second... 8)
Reply | Report Abuse | Link to thisThe symmetry makes me wonder if we are not seeing some mirroring?
Reply | Report Abuse | Link to thisThat an artist's conception is necessary to illustrate the described bubbles of Fermions(?) makes one wonder what the researcher's data indicates, if anything. While the article's description seems to inspired some readers, I think it would have been helpful to have access to a prepublication version of the research paper.
Reply | Report Abuse | Link to thisIMO, the illustrated fermion 'bubbles' appear to be located precisely where any remaining residue from the relativistic expulsion jets produced by a previously active Milky Way galaxy should be expected.
Reply | Report Abuse | Link to thisI suggest that the highly energetic particles that appear to be emitting gamma rays at the polar axes of the Milky Way galaxy are the residual of a prior period of supermassive black hole activity at the galactic core.
As I understand, when black holes 'ingest' matter, it is fundamentally disintegrated as it is accelerated to luminal speeds; its component fundamental particles are ejected via polar jets, while its gravitational energy is incorporated within the black hole.
When matter is no longer being actively 'ingested' by the black hole, these two polar jets of high velocity fundamental particles should be expected to decelerate, leaving a residue of highly energized fundamental particles where the relativistic jets had been located. I suggest these are the inferred polar gamma ray emitters.
Expanding on the idea that these gamma ray emissions could indicate past periods of galactic nucleus activity, it's unclear that any more than this could be detected from an active galaxy.
Reply | Report Abuse | Link to thisIf our galaxy was currently directing collimated streams of fundamental particles away from us at relativistic speeds, the only evidence we might be able to observe is some ancillary emissions, such as gamma rays produced by collisions among particles accelerated to nearly luminal speeds.
Not only are these 'Fermi bubbles' likely residual evidence of past periods of galactic core activity, but might possibly indicate that the Milky Way currently has an active galactic nucleus.
I'll disregard TAWilliams01's rantings, bot Tofara may have a point.
Reply | Report Abuse | Link to thisHowever, after all I've heard/read about black holes, it seems they should be rather be termed grey holes, if highly energetic matter can escape.
Of course, it may all be a question of distance, the speedy particle gets away, while the laggard gets cought in the black hole.
If our galaxy has these bubbles, then all other galaxy should have them too. Why then for example they can‘t be seen in the nearby Andromeda galaxy?
Reply | Report Abuse | Link to thisvagnry; dantevialetto:
Reply | Report Abuse | Link to thisThe requested link to the prepublication research paper has now been added (Thanks! - I haven't read it yet): "Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?",
http://arxiv.org/abs/1005.5480v3
The 'AGN Activity' in its title refers to 'Active Galactic Nucleus Activity' as I speculated. Please see:
http://en.wikipedia.org/wiki/Active_galaxy
for more information.
vagnry: IMO, it makes no difference how much matter escapes from a black hole, as long as no gravitational energy does.
dantevialetto: re. detection in other galaxies: I'm only guessing, but the gamma rays may be so disperse that their detection in other galaxies may be very difficult, especially if they occur only in active galaxies.
Also, I wonder if their apparent 'bubble' configuration could be an artifact of our persepctive of some relativistic phenomena.
it is assumed that gravity must attract the plasma. or gas into the galaxy ..... otherwise there should be a force that repels the plasma.
Reply | Report Abuse | Link to thisse supone que la gravedad debe atraer al plasma. o sea al gas hacia la galaxia.....en caso contrario debe existir una fuerza que repele el plasma.
se supone que la gravedad debe atraer al plasma. o sea al gas hacia la galaxia.....en caso contrario debe existir una fuerza que repele el plasma.
Reply | Report Abuse | Link to thisit is assumed that gravity must attract the plasma. or gas into the galaxy ..... otherwise there should be a force that repels the plasma
it is assumed that gravity must attract the plasma. or gas into the galaxy ..... otherwise there should be a force that repels the plasma
Reply | Report Abuse | Link to thisse supone que la gravedad debe atraer al plasma. o sea al gas hacia la galaxia.....en caso contrario debe existir una fuerza que repele el plasma
how long has this been going on?
Reply | Report Abuse | Link to thiswhat we have here is a failure to communicate...
no, las estrellas vienen.
Reply | Report Abuse | Link to thisMay I suggest you all have read over this series of papers:
Reply | Report Abuse | Link to thistheresonanceproject.org/pdf/origin_of_spin.pdf
theresonanceproject.org/pdf/AIP_CP_SProton_Haramein.pdf
theresonanceproject.org/pdf/quaternions_spinors_twistors_paper.pdf
Its sets out why such a phenomenon would be observed and is not unexepected in the model.
Thanks.
The artist's conception does not match the description of 'tear drop' or 'hot air balloon'. I'm curious if the bubble is narrower near the centre of the galaxy or further away, and how it matches against the known event horizon of the central black hole.
Reply | Report Abuse | Link to thisAlso, I suspect the colours are misleading, and do not indicate energy emission densities.
Finally, I'm curious about whether the two bubbles are in fact as homogeneous and symmetrical as pictured, or just rendered as such out of convenience.