The Answer to the Question…

How do you search out unusual types of “cosmic stuff” such as dark matter and antimatter?  The response:  you do particle physics.  Now, what’s particle physics?  It’s the science of understanding the makeup and actions and effects of particles (atoms and their constituent components the electrons, quarks, etc.) that make up matter in the universe.

Cosmic rays are a big part of particle physics. They are pieces of atoms called “subatomic particles” that are very energetic.  They zip around the universe at high speeds, they can penetrate our planet’s atmosphere and the surface,  and even your body.

The next shuttle launch (the last one for Endeavour) will take a unique experiment into space called the Alpha Magnetic Spectrometer (AMS for short).  It will be left on the International Space Station and spend some time doing particle physics.  In its search for antimatter (which is the “anti” version of regular matter), the AMS will look for what’s called an “antihelium” nucleus occurring naturally in the universe. This “stuff” has been observed before in collider experiments where they have been created briefly during high-speed particle collisions.  The instrument is sensitive enough to detect such antimatter at tremendous distances — out to the limits of the expanding universe (where, in its early  moments, there may have been antimatter created as a part of the birth of the cosmos).

The AMS also sets its sensitive sights on the detection of dark matter, that stuff that appears to make up some 95 percent of the mass of the entire universe.  There’s a LOT of it out there, and eventually we’re going to find out what it is.  The AMS will look at the background amounts of positron, anti-proton, or gamma-ray flux (or type of flow). If there are peaks (or jumps) in the flux, then this may tell us about the presence of dark matter (and what it is).

Of course, since the AMS will be in space, studying space, it will give us a lot of information on the cosmic ray counts we encounter in near-Earth space. Cosmic rays come from a variety of sources (including supernova explosions, the Sun, and so on), and knowing the cosmic ray environment at both normal and peak levels helps us understand their role and existence.  In addition, anybody venturing off Earth — whether to the Moon, the ISS, Mars or wherever — has to be continually aware of the cosmic ray levels. These babies are lethal in high doses!

So, how does this weird-looking instrument do its work? It has a set of detectors that are “interested” in various particles.  For example, the transition radiation detector clocks the speeds of very high-energy particles, as does the ring-imaging Cherenkov detector. The AMS also has a superconducting magnet that is strong enough to bend the path of a charged particle and allows it to be identified. Other instruments measure the energy of the particles as they pass through, and give some indication of their coordinates in the magnetic field of the superconducting magnet.  This all makes sense once you understand that these particles are creatures of their magnetic environments and so using speed detectors and magnets to measure their characteristics is the way to go.

While much subatomic physics can be done on the ground at places like CERN and Fermilab and Brookfield National Laboratory (among others), such experiments are usually better conducted in space, away from the Earth’s environment and where the conditions can be more easily understood.  This flight of the AMS module (officially called AMS-02) is another step in stretching our understanding of the smallest particles (and their actions).  For more information about AMS-02, visit the instrument Web page, where you’ll find introductory material, images, and videos.