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Swift
2010-Nov-10, 03:11 PM
From R&D Magazine (http://www.rdmag.com/News/2010/11/Astrophysics-Astronomers-find-giant-previously-unseen-structure-in-our-galaxy/)

NASA's Fermi Gamma-ray Space Telescope has unveiled a previously unseen structure centered in the Milky Way -- a finding likened in terms of scale to the discovery of a new continent on Earth. The feature, which spans 50,000 light-years, 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 (CfA) in Cambridge, Mass., who first recognized the feature. "We don't fully understand their nature or origin."

At more than 100 degrees across, the structure spans more than half of the sky, from the constellation Virgo to the constellation Grus. It may be millions of years old.

A paper on the findings will appear in an upcoming issue of The Astrophysical Journal.

antoniseb
2010-Nov-10, 09:51 PM
It will be interesting to eventually know the process that caused the bubbles. Was it something as simple as a star getting eaten by SgrA*?

Cougar
2010-Nov-11, 02:13 AM
Thanks, Swift!

The article finally said:







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 that the Milky Way's black hole sports such a jet today, it may have in the past.

Duh?

The article mentioned another possibility: "gas outflows from a burst of star formation, perhaps the one that produced many massive star clusters in the Milky Way's central light-years several million years ago." Wouldn't that be more omni-directional rather than the apparent bi-symmetry of these apparent BH jet remnants?

CosmicUnderstanding
2010-Nov-11, 04:52 AM
25,000 light-years in both directions..astonishing! Please keep us informed if you happen to stumble across any updates on this.

noncryptic
2010-Nov-11, 04:01 PM
It will be interesting to eventually know the process that caused the bubbles. Was it something as simple as a star getting eaten by SgrA*?

Could that involve enough energy to cause two gamma ray bubbles 25000ly across?
I don't know, but it seems unlikely.

Hungry4info
2010-Nov-11, 05:18 PM
Could that involve enough energy to cause two gamma ray bubbles 25000ly across?
I don't know, but it seems unlikely.

Well the particles are going to keep on going their merry way. If it happened long enough ago, I see no reason the particles couldn't end up at their observed locations.

Glom
2010-Nov-11, 08:02 PM
Why are these particles still spewing gamma rays after all this time?

antoniseb
2010-Nov-12, 05:58 PM
Could that involve enough energy to cause two gamma ray bubbles 25000ly across?
I don't know, but it seems unlikely.

I don't know either, but I expect that if a 20-50 solar mass WR star falling in, getting magnetically disrupted, and blasting 1060 relativistic protons or alphas (if they survive the event) out the poles should result in a fairly long duration event as these things hit the ISM. Could it be what we're seeing? I haven't looked up the numbers to even start the back-of-envelope calculation.

Michael Noonan
2010-Nov-13, 01:31 AM
It wouldn't surprise me if the bubbles were more like an hourglass structure with an undefined outer edge and showing apparent superluminal velocity. In accordance with Bautforum rules this is only an expressed opinion and I will wait until the facts are posted from the proper authorities.

Jerry
2010-Nov-13, 10:11 PM
Every time we come across a new observations that was not predicted by any theory, one of the usual suspects is trotted out: Dark Matter, Dark Energy or Black Holes. Since this type of double-bubble phenomenon is not a predicted attribute of black holes; it would be best to simply release the data. We don't have a good causal mechanism for the gamma rays emitted by lightning. If we could develop one, it might be a better jump-off point for developing the physics necessary to explain gamma rays on a galactic scale.

noncryptic
2010-Nov-14, 02:03 PM
Every time we come across a new observations that was not predicted by any theory,one of the usual suspects is trotted out: Dark Matter, Dark Energy or Black Holes.

What alternative do you propose?


Since this type of double-bubble phenomenon is not a predicted attribute of black holes;

Black Holes ejecting stuff at the poles is predicted by theory (galactic jets). These bubbles could be a small version of that. Eat a lot: eject jets. Eat a little: burp.


it would be best to simply release the data.

What, they are keeping it secret?

Jerry
2010-Nov-15, 02:12 AM
What alternative do you propose?

Unexpected observations don't have to be tied to other things that are poorly understood. It is hard to come up with an analogy, because I can't think of a similar approach in other disciplines. 'We don't have a good handle on what causes gamma rays, so it must be one of these other phenomenon that we have a poor understandling of.' Just because something goes bump in the night doesn't mean there is a ghost...or a prowler.


"Black Holes ejecting stuff at the poles is predicted by theory (galactic jets). These bubbles could be a small version of that. Eat a lot: eject jets. Eat a little: burp.'

If it is that simple, why so unexpected? Or is 'unexpected' just hype? I don't think accretion should result in bubbles, but maybe the bubble is a simplified explanation.


What, they are keeping it secret? No. when something is not understood; hanging it on a tree that may not even exist is like knowing someone is lost and pointing in one direction and saying "they might have gone that way". Don't send the search party off in one direction, when a more honest assessment of the situation would be to say 'we just don't know - let's look at all possible paths.'

Another example of using leprechons to explain unicorns:

http://arxiv.org/abs/1011.2801

Gamma rays from dark matter

OR

If you prefer, using Black Holes as an alternative to cuspy dark matter:

http://arxiv.org/abs/0911.2232

And while were at it, let us not forget that Dark Energy can be used to explain quinessence:

http://arxiv.org/abs/1005.1278


We then apply our method to the case of coupled quintessence, where the fifth force acts among cold dark matter particles, and to growing neutrino quintessence, where the fifth force acts between neutrinos. Furthermore, we review this method within standard cosmologies and apply our analysis to minimally coupled quintessence. We also check past results for early dark energy parametrizations.

Strange
2010-Nov-15, 11:32 AM
Unexpected observations don't have to be tied to other things that are poorly understood. It is hard to come up with an analogy, because I can't think of a similar approach in other disciplines.

Here's an analogy: black swans. Rather than invent a new explanation (an entirely new species), it is easier to say, "oh look, swans come in black as well".

Or contagious diseases; whenever a new disease crops up it is easier to assume it is caused by the known agents (bacteria, virus, etc). But very, very occasionally (and this is just for you :) a completely knew mechanism of contagion is found (e.g. prion diseases). These, inevitably, need a lot of evidence and take some time to be accepted (I think there are still some people unconvinced by the prion hypothesis). But you can't just say that this looks unusual so everything we know must be wrong.

Jerry
2010-Nov-15, 06:08 PM
Here's an analogy: black swans. Rather than invent a new explanation (an entirely new species), it is easier to say, "oh look, swans come in black as well".

When is a black swan not a swan? When is a koala bear not a bear?

Sometimes a new species is the correct choice; and sometimes it is more difficult to make that choice when an erroneous label has been hung on something too soon.

NASA announced today that Chandra had isolated a newly formed black hole in the center of a supernova that occurred in 1979C. Buried in the announcement is the caveate that it might be a Neutron star. The difficulty lies in our lack of understanding of gamma ray production in general.

Black holes should not be blowing bubbles - there is a tentative mechanism for creating gamma rays in the shear plane of an accretion ring - but there is still a lot of speculation; and gaping holes in the science behind the assumptions. What should not be true, is that if you say it 'might be' enough times, a weak and speculative scientific theory should become a consensus scientific fact. A koala is not a bear; a bubble is not an accretion ring.

Another example is the theory that flowing magna is responsible for the Earth's magnetic field. Since magna is above the eutectic point for most metals; I have always found this theory curious. As near as I know there is no direct evidence supporting this conjecture; but everyone seems to know that if the earth did not have flowing magna, there would not be a magnetic field. Really?

Swift
2010-Nov-15, 06:59 PM
Another example is the theory that flowing magna is responsible for the Earth's magnetic field. Since magna is about the eutectic point for most metals; I have always found this theory curious. As near as I know there is no direct evidence supporting this conjecture; but everyone seems to know that if the earth did not have flowing magna, there would not be a magnetic field. Really?
Let's not sidetrack this thread with that discussion. If you wish to discuss this, please start a new thread in Science & Technology.

And even the metadiscussion about unexpected observations is getting a little off the topic of this thread. Please make sure that this discussion is particular to the gamma ray bubbles of the OP.

Thank you everyone.

Jerry
2010-Nov-15, 09:14 PM
Agreed. The bubbles are curious, quite well defined. The NASA article mentions that WMAP observed a similiar feature in the microwave range; but I am unfamiliar with this data. Streaking ions (or cations) in a strong magnetic field would create microwaves; and colliding with the galactic equivalent of a helopause could define a pair of bubbles. But what is accelerating these particles enough to produce a bubble-shaped array of gamma rays?

Boratssister
2010-Nov-16, 08:17 PM
Very strange indeed....... Any other galaxies have these bubbles? Would it be even possible to image other galaxy bubbles?
Are these bubbles made out of some super radioactive material? is it the remnants of some sort of super nuclear explosion?

Jerry
2010-Nov-17, 07:56 PM
http://arxiv.org/abs/1011.3477

Cosmic Jets



We discuss time-dependent gravitational fields that "accelerate" free test particles to the speed of light resulting in cosmic double-jet configurations. It turns out that complete gravitational collapse along a spatial axis together with corresponding expansion along the other two axes leads to the accelerated motion of free test particles up and down parallel to the collapse axis such that a double-jet pattern is asymptotically formed with respect to the collapsed configuration.

forrest noble
2010-Nov-17, 09:43 PM
Boratssister,


Very strange indeed....... Any other galaxies have these bubbles? Would it be even possible to image other galaxy bubbles?
Are these bubbles made out of some super radioactive material? is it the remnants of some sort of super nuclear explosion?


I've seen such claims over the years concerning just one observed cloud in other galaxies moving away from the galactic center. It must be very difficult to see them since apparently we have just found both of them now and this is our own galaxy. As I recall one of the clouds has been known since the 1970's. My guess is that they can't be too old, maybe less than a hundred million years because they still have active quantities of positrons within them that enable us to see the resulting gamma rays. If they were a lot older than that I would expect that from their distances gamma rays would no longer be detectable here on Earth because the active quantities of positrons seemingly would have dwindled. They may only be feeding burps as was discussed or they could be evidence for another process.

As I recall, such gamma ray producing clouds are also a prediction concerning some other cosmological models.

BTW, Borat's sister wasn't bad looking according to the movie :) :)

Boratssister
2010-Nov-17, 11:05 PM
Boratssister,



I've seen such claims over the years concerning just one observed cloud in other galaxies moving away from the galactic center. It must be very difficult to see them since apparently we have just found both of them now and this is our own galaxy. As I recall one of the clouds has been known since the 1970's. My guess is that they can't be too old, maybe less than a hundred million years because they still have active quantities of positrons within them that enable us to see the resulting gamma rays. If they were a lot older than that I would expect that from their distances gamma rays would no longer be detectable here on Earth because the active quantities of positrons seemingly would have dwindled. They may only be feeding burps as was discussed or they could be evidence for another process.

As I recall, such gamma ray producing clouds are also a prediction concerning some other cosmological models.

BTW, Borat's sister wasn't bad looking according to the movie :) :)

High five forrest.
Yep these bubbles are blowing my mind....... Could it be some galactic magnetic field capturing these positrons? lets hope time will tell.

forrest noble
2010-Nov-18, 12:06 AM
High five forrest.
Yep these bubbles are blowing my mind....... Could it be some galactic magnetic field capturing these positrons? lets hope time will tell.

Yeah, I think it's strictly a matter of theory from here on out. I can't imagine how they might prove that these clouds were produced by a burp or otherwise. The simplest standard-model explanation I think would be that it is a burp from a recently consumed torus maybe 20-100 million years ago. There is a magnetic field involved but the destruction of existing matter by black hole forces could explain the production of large quantities of positrons. Positron annihilation however the positrons were produced, seems to be the most likely cause of the gamma rays produced by these bipolar clouds.

mantiss
2010-Nov-18, 04:45 AM
I don't see how it would be unexplainable, just because sloppy thinking never envisioned such jets means we need to say it was unforeseen, it just means that we suck at imagining how the quiet and peaceful Milky Way could have had a more lively past. :)

Glom
2010-Nov-19, 08:28 AM
http://arxiv.org/abs/1011.3477

Cosmic Jets

Meaning what?