http://www.eurekalert.org/pub_releases/2005-03/ppa-uth032205.php "In the March 25th 2005 issue of Science Magazine, the High Energy Stereoscopic System (H.E.S.S.) team of international astrophysicists, including UK astronomers from the University of Durham, report results of a first sensitive survey of the central part of our galaxy in very high energy (VHE) gamma-rays. Included among the new objects discovered are two 'dark accelerators' - mysterious objects that are emitting energetic particles, yet apparently have no optical or x-ray counterpart. " So,what can be these "dark accelerators"?. Any suggestion?
If they radiate in gamma rays alone, they must be so hot that their blackbody emission curve doesn't extend into the X-ray or UV spectrum. The smaller a star collapses, the hotter it becomes; a newly-formed neutron star would have a surface temprature of billions of degrees, and would shine mostly in X-rays. Perhaps these objects are far smaller and hotter yet... hyperon stars? Even naked singularities of some kind? (I'm kidding...) Or perhaps these gamma sources are artificial - genocidal weapons in a cosmic war, designed to irradiate and sterilize whole planetary systems? Or just the by-product of a elder civilisation's stellar-sized power plants? We did have a thread recently which discussed the possibility of a gammasynthetic biosphere - these dark accelerators might be surrounded by a swarm of inhabited worlds whose biology/technology operates on a far higher energy level than ours.
Hum, Well i` m sure that most ppl would be thinking <b>dark matter</b>…. I imagine that super symmetric neutralino annihilation into gamma rays, neutrinos and synchrotron emission from dark matter clumps, a light year in size, could be the source. However, the strongest signals would be found to come from the Galactic Centre and from the nearby dwarf spheroidals, and not just confined to just the galactic disk… (<i>though, it could be the interaction of darkmatter clouds and normal matter clouds in the spiral arms</i>) But, it looks like it’s a new type of phenomena. So, for the time being, alien technology seems a novel (but unlikely , imho) alternative… Please Register or Log in to view the hidden image!
oh no... they are coming Please Register or Log in to view the hidden image! evacuate!! ~~~~~~~~~~~~~~ But seriously though this is very interesting news. Thank you for bringing this up, Lucas! Umm.. if the survey found two of these in one our galaxy, then these "accelerators" should be fairly common throughout the known universe, right? I wonder how they could "look" like. p.s. Maybe I missed it in the article and I understand that not long enough time has passed since the discovery, but I wonder how stable these accelerators are, i.e., how long they last.
No, there was nothing in the article about that. What I missed on my first scan of the article was that they seem to extend over several lightyears - so, rule out the tiny hyperon star idea! Unless the gamma rays from a point source are being refracted and scattered by surrounding nebulosity... Diffuse gas in space can have effective temperatures of millions of degrees, even over the entire volume of a cluster of galaxies. Perhaps these are simply smaller clouds with even higher temperatures - heated by intense magnetic fields, perhaps, or indeed by matter-antimatter annihilation as Cato suggested. But as for where large quantities of antimatter might be originating... that's another problem.
I think they are waiting for additional information and study before suggesting what seems to be a focus in the experiments. Dark matter, as blobrana suggested. Here is an excerpt and a link to an article from CERN last September: "The Galactic Centre has long been predicted as a source of VHE gamma rays generated in the accumulation and annihilation of dark-matter particles, for example the lightest stable supersymmetric particles. The characteristics of the gamma-ray signal detected by HESS are indeed consistent with the expected features for dark-matter annihilation, but would require very heavy (> 10 TeV) dark-matter particles and a large annihilation rate or enhanced density of the dark matter at the Galactic Centre. More conventional explanations include particle acceleration in the 10,000-year-old supernova remnant Sagittarius A East, which is still consistent with the HESS error circle for the source location. Future data should pin down the source location even better." http://www.cerncourier.com/main/article/45/1/22
Hm; dark matter annihilation, eh? We were considering using that as a cheap energy source and as a weapon over at OA, but the problem is gathering large concentrations of dark matter in one place. Dark matter seems to interact with normal matter only via gravity, which is a very weak force; we considered building rings of blackholes to gather dark matter and produce 'enhanced density', but our physics gurus reckon black holes would have a dispersive effect. Instead of concentrating the dark matter the black holes would spread it out. If there is a civilisation at the centre of the galaxy they might have solved this problem... (my money would be on particle acceleration associated with Sag A, but you never know...)
Hum, Tnx for that CERN link. So, to me, symmetric neutralino now seem to be <b>too light</b> to account for the high energies! That, with the lack of other VHE sources not in the galactic plane, seems to knock the Dark matter idea out.... Oh well.... <font color=blue>< random image ></font> Please Register or Log in to view the hidden image! <font color=blue>< /random image ></font>
Whoops, There`s a better photo here: http://www.mpi-hd.mpg.de/hfm/HESS/public/PressRelease/PressRelease.html Please Register or Log in to view the hidden image! (picture is only 25kb in size moderator ...)
blobrana, I understand the HESS Cherenkov telescope was specifically built at its location in the southern hemisphere to study the galactic plane and center the Milky Way, and not other galatic sources of gamma-rays, such as galaxy PKS 2155-304, which was discovered by Whipple in 1989 as being a source of tera-electron-volt (TeV) gamma-rays. HESS has discovered eight NEW sources of gamma-rays in our own galaxy. TWO of these sources are very unusual as they do not emit EM radiation in other wavelengths, different than Sag A and previously known sources. The new Dark Accelerators are not at Sag A's location, the CERN article is 6 months old and was published before these new discoveries. Most sources of VHE gamma-rays are thought to be supernovas, plusars and supermassive black holes such as the one in the center of our galaxy. Neutralinos are certainly not the only theorized dark matter particles, there are several supersymmetric particles theorized. What makes these two new Dark accelerators interesting is the fact they DON'T emitt EM radiation in other wavelengths. We have telescopes that 'see' in x-ray, infrared, optical and radio wavelengths and these two sources seem to be invisible in those wavelengths, hence the possibility of dark matter as being their engine. Remember, the very definition of Dark Matter is that it does not emitt or reflect EM wavelengths, or at least no wavelength that has been detected before. Whether the gamma-rays are from proton annihilation or whatever, the SOURCE of the acceleration is not detected in EM wavelengths, so this may be entering into new physics. A cut & paste: "The field of the Galactic Centre shows, in addition to the strong source close to Sagittarius A*, a second source, which appears to be associated with the pulsar nebula inside the supernova remnant G0.9+0.1. Similarly, observations targeted at the pulsar PSR B1259-63 have revealed - besides a gamma-ray signal from the pulsar - evidence of a second source about 0.6° north of the pulsar. This source HESS J1303-631 could not so far be associated with a counterpart in other wavelength regimes and may represent a type of cosmic accelerator hitherto unknown."
Hum, (Sry dont understand what/who you were correcting/pointing out) >>Neutralinos are certainly not the only theorized dark matter particles. Yeah, the dark matter particles would have to be slightly heavier, er, to account for the VHE. (BTW, Its darkmatter and anti darkmatter annihilation that’s supposed to generate the gamma rays) It’s just that Neutralinos are the current flavour of the day. (But i don't discount some exotic interaction of darkmatter and baryonic clouds that could create some sort of dark tori accelerator) And since there are 10 or more dwarf spheroidial satellite galaxies well above and below the galactic plane we should also see other sources that are not associated with supernova/pulsar etc (and do not emit EM radiation in other wavelengths).
Sorry, blobrana, I more or less was responding to the speculations in the thread. eburacum45 stated his money was on Sag A as the source of the Dark accelerators. I pointed out that the dark accelerators were not in Sag A, that the CERN article was from very early results. You, blobrana, seemed to be focusing on neutralinos as the only particle, or favored particle, to represent dark matter. The light neutralinos are a hot dark matter candidate, but observations over the last few years favor Cold Dark Matter, such as WIMPS, which are very heavy. The neutralinos were the flavour of the day in the '80's, but not today. Both hot and cold dark matter may exist, but it is currently theorized that about 80% of the dark matter would be cold (CDM). Here is a basic description and understanding of CDM: "Although the existence of WIMPs in nature is hypothetical at this point, their existence would resolve a number of various astrophysical and cosmological problems related to dark matter. The main theoretical characteristics of a WIMP particle are: (1)Interaction only through the weak nuclear force and gravity (2)Large mass compared to standard particles. Because of their lack of interaction with normal matter, they would be dark and invisible through normal electromagnetic observations. Because of their large mass, they would be relatively slow moving and therefore cold. As result they would tend to remain clumpy. Simulations of a universe full of cold dark matter produce galaxy distributions that are roughly similar to that which is observed. WIMPs are considered one of the main candidate for "Cold Dark Matter", the other being MACHOs. (These names were chosen to be in stark contrast, intentionally with MACHO being named later than WIMP's). Also, in contrast to MACHOs, there are no known particles within the standard model of particle physics which correspond to WIMP's. The particles which have little interaction with normal matter such as neutrinos are all very light, and hence would be fast moving or hot. Hot dark matter would smear out large scale structure of galaxies and is not considered a viable cosmological model. WIMP-like particles are predicted by supersymmetry although none of the large numbers of new particles in supersymmetry have been observed." http://en.wikipedia.org/wiki/WIMP
Hum, I really must keep up to date…. It seems that from that link you gave that indeed the formation of galaxies etc do require an input of slow moving cold dark matter, that began to coalesce very early on: And yeah, that might be the key. The heavier particle would produce the higher energies seen. If that type of dark matter began to clump together very early on and `seed` the universe, I imagined that most of it (from our Milky Way point of view) now resides within the massive black hole at the centre, or be confined nearby. (Note to myself: It can’t be <i>too</i> heavy) (This of course problematically still poses the question as to why the Magellanic Clouds or the ten or more dwarf satellite galaxies don’t have gamma ray exclusive sources – or have they simply been overlooked?) All this would still require a `hot` component (including, by now, clouds) to make up the halo mass. (Otherwise where are they?).
