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Fraser
2004-Sep-22, 04:53 PM
SUMMARY: Something is radiating high-energy gamma rays at the heart of our Milky Way galaxy, and astronomers aren't sure what it is. The object was discovered using the High Energy Stereoscopic System (H.E.S.S.), an array of four telescopes, in Namibia, South-West Africa. One theory is that it's the remnant from a supernova that exploded 10,000 years ago; this has enough energy to accelerate gamma rays so strongly. The object is also very near the supermassive black hole at the centre of the Milky Way, so this radiation could be somehow associated with it.

What do you think about this story? Post your comments below.

antoniseb
2004-Sep-22, 05:23 PM
I like these stories because it tells us reasons to make even better intruments. It is pretty clear from the image that we'll know the source of the high-energy photons when we can get an angular resolution better than about 500 milli-arc-seconds.

When we can do that we will probably see that both sources contribute to some degree, but the spectra will be different.

BTW, this is not the only question that such an instrument could answer. There are other sources of High Energy Photons out there, and eventually we'd like to identify the sources of them. Such an instrument could help nail down the strong close ones. So far, except for the galactic center, we've got nothing.

om@umr.edu
2004-Sep-22, 05:39 PM
Thanks, Fraser, for another interesting mystery.

I see these quotes as signs that astrophysics is ripe for major revision.

"One theory is that it's the remnant from a supernova"

"However, the team's theory doesn't fit with earlier results"

"Science continues to throw out the unexpected as we push back the frontiers of knowledge"

"The centre of our Galaxy is a mysterious place, home to exotic phenomena such as a black hole and dark matter"

"It is possible that the gamma-ray source at the Galactic Centre varies over the timescale of a year"

"The H.E.S.S. team hopes to unravel the mystery with further observations"

I doubt if we can decipher exotic events at the centre of our Galaxy without first resolving major differences of opinion about happenings in the interior of the star next door.

With kind regards,

Oliver
http://www.umr.edu/~om

StarLab
2004-Sep-22, 06:00 PM
Except we&#39;re not next to a black hole, Oliver&#33; :rolleyes: <_<


The object is also very near the supermassive black hole at the centre of the Milky Way, so this radiation could be somehow associated with it. No sh*t&#33; <_< :rolleyes: :lol: :P ;)

I think it is pointless to speculate and guess, and first we should at least get some better observations before we come up with tens of incorrect theories.

Tiny
2004-Sep-22, 06:14 PM
By any chance, if we can find several more of the Supernoa explosion going on in the heart of the Milky Way Galaxy, do you think that will cause the Super massive black hole to become reactive again?

antoniseb
2004-Sep-22, 07:13 PM
Originally posted by om@umr.edu@Sep 22 2004, 05:39 PM
I doubt if we can decipher exotic events at the centre of our Galaxy without first resolving major differences of opinion about happenings in the interior of the star next door.
I am unaware of any major difference of opinion about what is happening in the interior of the sun. Can you elaborate without citing your own work? Who currently disagrees about a major aspect of the sun&#39;s interior to the degree that it affects how we understand the observations of the Extremely High Energy Gamma Rays from the galactic core?

antoniseb
2004-Sep-22, 07:17 PM
Originally posted by Tiny@Sep 22 2004, 06:14 PM
do you think that will cause the Super massive black hole to become reactive again?
The black hole in the center will sometimes flare up. Supernovae going off near it will result in small flares [detectable but not dangerous]. What would really make it give off lots of energy would be for a gas cloud to fall into the galactic center, or a merger with another galaxy.

lswinford
2004-Sep-22, 08:12 PM
I seem to recall some earlier articles, here and elsewhere, describing the galaxy center, the yoke of our fried egg if you will, as a very energetic region. Suppose there is some sort of line we should broadly draw to say that the environment inside is too hostile, too toxic, for humankind? I suppose that exists even in our own solar system where things are distinctly too &#39;hot&#39; without extraordinary shielding and environmental protective support. So where would we, or would we in the first place, have to say that if there are living things there, they would have to be radically different living things, for living things like us couldn&#39;t survive the ambient radiation and other environmental hazards?

antoniseb
2004-Sep-22, 08:35 PM
Originally posted by lswinford@Sep 22 2004, 08:12 PM
Suppose there is some sort of line we should broadly draw to say that the environment inside is too hostile, too toxic, for humankind? I suppose that exists even in our own solar system where things are distinctly too &#39;hot&#39; without extraordinary shielding and environmental protective support.
As you noted, just flying around outside Earth&#39;s magnetic protection is a risk from solar flares. Getting near Jupiter would require some serious precautions. Now, we are not going to the center of the galaxy anytime soon, but when humans do go, I expect they will be inside a very large piece of rock with walls half a mile thick, and a fairly intense magnetic field around it.

om@umr.edu
2004-Sep-23, 04:13 AM
Originally posted by antoniseb@Sep 22 2004, 07:13 PM
I am unaware of any major difference of opinion about what is happening in the interior of the sun.

Can you elaborate without citing your own work?
In the forward to the 1988 nuclear astrophysics textbook by C. E. Rolf and W. S. Rodney, Caldrons in the Cosmos: Nuclear Astrophysics,

The Nobel Laureate astrophysicist, William A. Fowler, pointed out two serious difficulties in the most basic concepts of nuclear astrophysics:

1. “On square one the solar neutrino problem is still with us (…), indicating that we do not even understand how our own star really works.”

2. “On square two we still cannot show in the laboratory and in theoretical calculations why the ratio of oxygen to carbon in the Sun and similar stars is close to two to one (…)”

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2004-Sep-23, 01:40 PM
Originally posted by om@umr.edu@Sep 23 2004, 04:13 AM
1. “On square one the solar neutrino problem is still with us (…), indicating that we do not even understand how our own star really works.”
Of course, THAT was sixteen years ago. The solar neutrino problem seems pretty well resolved now. No controversy.

om@umr.edu
2004-Sep-23, 01:43 PM
Originally posted by StarLab@Sep 22 2004, 06:00 PM
Except we&#39;re not next to a black hole, Oliver&#33; :rolleyes: <_<


Right, StarLab.

There is some doubt that black holes exist,
or that neutron stars collapse into black holes.

But, there is something exotic in the Sun,
probably a neutron star.

With kind regards,

Oliver
http://www.umr.edu/~om

om@umr.edu
2004-Sep-23, 01:58 PM
Originally posted by antoniseb@Sep 23 2004, 01:40 PM
The solar neutrino problem seems pretty well resolved now. No controversy.
Anton,

I was at the NO-VE conference on Neutrino Oscillations in Venice last December.

That was less than a year ago.

The 1st serious difficulty that Fowler noted in the most basic concepts of nuclear astrophysics,

1. “On square one the solar neutrino problem is still with us (…), indicating that we do not even understand how our own star really works”,

was clearly not "pretty well resolved" then &#33;

I was at the conference on Nuclei in the Cosmos in Vancouver, BC this summer.

That was less than three months ago.

The 2nd serious difficulty that Fowler noted in the most basic concepts of nuclear astrophysics,

2. “On square two we still cannot show in the laboratory and in theoretical calculations why the ratio of oxygen to carbon in the Sun and similar stars is close to two to one (…)",

was the main concern of many papers, clearly not "pretty well resolved" &#33;

With kind regards,

Oliver
http://www.umr.edu/~om

antoniseb
2004-Sep-23, 02:06 PM
Originally posted by om@umr.edu@Sep 23 2004, 01:58 PM
2. “On square two we still cannot show in the laboratory and in theoretical calculations why the ratio of oxygen to carbon in the Sun and similar stars is close to two to one (…)"
Concerning this abundance ratio of Carbon and Oxygen, just how does that affect how we understand the observations of the Extremely High Energy Gamma Rays from the galactic core [the topic of this thread]?

GOURDHEAD
2004-Sep-23, 02:14 PM
One theory is that it&#39;s the remnant from a supernova that exploded 10,000 years ago; this has enough energy to accelerate gamma rays so strongly .

Either my comprehension or the wordsmithing needs a little help here. Gamma rays cannot be accelerated; however the medium generating them can and the resulting velocity can blueshift them to harder varieties. Also, the sentence seemed to end more abruptly than I expected. (If I am practicing logical error correction in this evaluation, how will we ever get AI to do this effectively?)

It is not beyond my infertile imagination to guess that several hundred solar masses of ionized material consisting of each of the known elements is orbiting the MW central SMBH in its accretion disk. This environment would consist of extremely dense gravitational, electric, and magnetic fields coupled in unimaginable ways. The charged particles will be traveling at near light velocity--very near--under constant acceleration in the intense magnetic field. This will give rise to synchrotron and, perhaps, Cerenkov (this environment [medium] is not well understood by us....maybe even brehmstralung) radiation some of which will satisfy the energy levels for gamma rays. As the ions reach accretion disk escape velocity, they can be flung away contributing to the population of cosmic rays.

Back to the allegation of acceleration, if it is not a careless bit of word smithing, should we infer that they have detected a rate of change of hardening of the gammas?