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Mystery Signal Could Be Dark Matter Hint In ISS Detector
astroengine writes Analysis of 41 billion cosmic rays striking the Alpha Magnetic Spectrometer particle detector aboard the International Space Station shows an unknown phenomena that is "consistent with a dark matter particle" known as a neutralino, researchers announced Thursday. Key to the hunt is the ratio of positrons to electrons and so far the evidence from AMS points in the direction of dark matter. The smoking gun scientists look for is a rise in the ratio of positrons to electrons, followed by a dramatic fall — the telltale sign of dark matter annihilating the Milky Way's halo, which lies beyond its central disk of stars and dust. However, "we have not found the definitive proof of dark matter," AMS lead researcher Samuel Ting, with the Massachusetts Institute of Technology and CERN in Switzerland, wrote in an email to Discovery News. "Whereas all the AMS results point in the right direction, we still need to measure how quickly the positron fraction falls off at the highest energies in order to rule out astrophysical sources such as pulsars." But still, this new finding is a tantalizing step in the dark matter direction.
In the past year, all of those have been eliminated. Dark Matter has to be something that doesn't not interact with light in any way except via gravity. I'm pretty sure "gas" interacts with light. Black holes is the only thing that fits this restriction, but the gravitational gradient would be too much, and would require 80% of the universes mass to be tied up in black-holes at the edge of galaxies.
You should have read the sentences right after where your quote stops:
"But we've been able to eliminate most of these as the primary variety in one way or another. If black holes constituted all of dark matter, for instance, we would expect to see gravitational lensing (the bending of light as it passes massive objects) when we look through the halo of our own galaxy at stars in other galaxies because we would expect there to be many black holes in that halo. We do not see such lensing, so we conclude that the dark matter we know to be present in galaxy is not black holes."
In other words, a lot of searches for microlensing and occlusion of stars within our galaxy have set an upper bound on the number of such items, and that upper bound is too small to cover a significant part of the missing dark matter. And that is without invoking the cosmological arguments for dark matter to be non-baryonic, and that there is more normal matter out that that we haven't even accounted for.
In the past year, all of those have been eliminated.
Most of those were weakened, if not eliminated over a decade ago, going back almost to some early surveys in the 90s. Not just in the past year. More and more studies keep reducing upper bounds on the number of such objects, but for some time that upper bound has been too low.
Dark Matter has to be something that doesn't not interact with light in any way except via gravity.
Dark matter can still interact with light, it just must do so weakly in a way that would match current observations. There are several detectors looking for various dark matter candidates passing through the detectors that would involve electromagnetic interaction, but such processes would be so dim in outer space that you couldn't see them from any distance.
I'm pretty sure "gas" interacts with light.
It also is something that has been mapped out a lot, and is baryonic.
, but the gravitational gradient would be too much, and would require 80% of the universes mass to be tied up in black-holes at the edge of galaxies.
The gradient is not a problem, nor would they all be right at the edge of the galaxy. A model using a gas of very small black holes spread through out the galaxy and halo would explain rotation curves just fine, as would it explain other things like gravitational lensing if there were clouds of black holes in certain places between galaxies. The problem with black holes is not that they couldn't explain the missing gravity source, but that they would have been observerable in various surveys specifically looking for them and were not.
The hypothetical "neutralino" is a family of four particles the lightest of which is considered to be a dark matter candidate. Neutralinos are their own antiparticles (similar to how photons are), and a pair of them can sometimes annihilate to form other matter-antimatter pairs of particles.
Dark matter simply means matter that is too small to be detected by what humans have so far developed to see, but which gravity study suggests should be there. Seventy years ago, Pluto was probably "dark matter". Giving a name to "everything" we can't see and then finding evidence that there's something more is a bit curious. What hasn't been "seen" yet is "dark". We will eat away at "dark" matter one snapshot at a time.
No, thats not correct. Dark matter is not matter that is "too small" to detect currently. Its matter that does not interact with electromagnetic radiation ( light, radio waves, gamma waves etc ) in any way, shape or form. We know its there from its gravitational interactions, that is correct. But it is not affected and does not affect electromagnetic radiation, or electric or magnetic fields. Its size is not the issue that makes it so difficult to detect.