Ah, dark matter. This invisible substance makes up about 84% of matter in the universe, or about 23% of the total mass-energy of the universe, and it has been giving astronomers a major headache since 1932. We see the effects of dark matter all around us, beyond that, the sum of all human knowledge on dark matter itself can fit very nicely on an invisible, non-existent piece of paper. After all, it’s tough to learn about something that can’t be seen directly with telescopes (for it doesn’t seem to emit or absorb any kind of light). Our only evidence supporting its existence at all is our ability to watch how it interacts with visible matter. Well, all of that could be about to change.
Meet the Alpha Magnetic Spectrometer (as seen near the center-left of the picture – the doughnut shaped thing attached to the ISS). This 15,000 pound, $2-billion, 15-year project is giving us a different kind of peak into the cosmos. Instead of analyzing parts of the electromagnetic spectrum – which has given us most of our astrophysical knowledge – the AMS system analyses cosmic rays. Here, scientists will search for positrons, electrons, dark matter, antimatter, and other particles which make up the universe.
The device itself is very cleverly designed. First, a particle must enter the AMS (duh), here the particle passes through several layers of detectors that will tell scientists the mass, energy, and velocity of the particle. In addition, these detectors will tell us where the particle came from in space, giving us an idea of where it originated from. Near the end of the particles journey, it will encounter a magnet which separates antimatter from regular matter.
Since the experiment went online in May of 2011, it has recorded about 25-billion particle events. Of that, about 8 billion of those events came from electrons and positrons, which could provide an important signature of dark matter annihilations. These experiments could go a long way to narrowing down what exactly dark matter is, giving credence or a lack thereof to a host of different theories. It could also go on to detect the existence of antimatter stars and or galaxies.
Information about exactly what the experiment found hasn’t been forthcoming, but an announcement is due to be made in about two weeks. Hopefully, we will have some good news.