Thursday, November 18, 2010

Antimatter Successfully Trapped At CERN.

Scientists at CERN (the European Organization for Nuclear Research) have succesfully trapped an antihydrogen atom.

Posted by Alexandru Nicolae

Image Credit: False colour image of Omega Nebula. NASA, ESA & J. Hester(ASU).
The successful trapping of an antihydrogen atom by physicists at CERN has been published in an advance letter to Nature journal. Scientists have known about antimatter for quite some time, and CERN has been studying it since 2002. Using a magnetic trap (an array of magnets), they were able to successfully contain an antihydrogen atom for fractions of a second. The implications for theoretical physics are vast, and more work needs to be done to fully understand this form of matter that was around at the big bang. But just exactly what is this stuff and what does it explain?

To give a brief physics overview, regular matter consists of a nucleus (a small, very dense center made of protons and neutrons), encircled by electrons (negatively charged particles that are similar to protons). The protons are positively charged (+), the electrons are negatively charged (-). This is the common view of what an atom looks like: 

Image Credit: University of Waterloo, Safety Office. Link.

It's also very incorrect, but to properly show what it really looks like would be nearly impossible; regardless, the model works well for explanation purposes so keep it in the back of your mind. Antimatter on the other hand is the nearly identical to the regular matter we're so familiar with, the only exception is that the charges are reversed. The protons are negatively charged and the electrons are positively charged.  The resulting antiparticles are called antiprotons and antielectrons (or positrons), respectively.

The main issue with successfully storing antimatter is that it doesn't seem to get along with regular matter. Whenever they meet they tend to react violently and annihilate in a burst of energy, this is the main reason we don't see antimatter floating around today. However, it was quite common at the time of the big bang, for some reason (still unknown at the moment), regular matter won out over antimatter, the remaining antimatter was annihilated and now only regular matter primarily exists in our universe. 

What the wonderful scientists and engineers at CERN did was use something called a magnetic trap (a very cool magnetic force field) to make antimatter from scratch; they brought antiprotons and positrons into their magnetic force field, and slowed them down with unbelievably low temperatures until they fused to form antihydrogen.. Their existence was short-lived before the newly created antihydrogen annihilated with matter (this showed up as flashes of light in the chamber), but it was long enough to do some scientific testing. 

One important question they have yet to test is based off of the colours that antimatter may emit in future studies. Matter, specifically elements like Hydrogen, emit characteristic coloured patterns of light when viewed through a tool called a spectroscope, this acts as a sort of finger print for the element and allows us to identify it even without physically observing it. Spectroscopy is how scientists found out the sun was made primarily of hydrogen; it is an invaluable tool in particle physics. The current theory is that antihydrogen will have these same patterns, showing that the two states are indeed identical for the most part. If this turns out not to be the case, some standard physics models for antimatter may need to be called into question.

This stuff isn't completely theoretical by the way. Antimatter does have practical uses, primarily in medicine. The PET scanner, or Positron Emission Tomography scanner, uses positrons to view what's going on inside of a patient whenever information concerning normal body function is needed. It works like this: a small amount of radioactive substance is injected into your veins which then gets absorbed by a tumor (or other metabolically active process). Once inside, the radioactive substance breaks down and releases positrons. The positrons then annihilate with matter in the tumor cells and gives off a burst of energy that can be detected by the scanner. The result is a 3D image that looks like this:

This is a powerful method for detecting unseen problems in the human body. It allows visualization of body physiology instead of body anatomy, the kind we're used to with X-rays.

I`m very excited to see where this research goes in the near future. It can open up our understanding of antimatter properties, help us figure out what happened in the split second moments after our universe came into existence, and even help those that are ill! The price to pay for these experiments may be large in terms of monetary investments, but the reward is well worth the costs. Investment in science pays off!

Advance Publication -
Andresen GB, Ashkezari MD, Baquero-Ruiz M, et al. (2010). Trapped Antihydrogen. Nature. Link here 
 Advance of the article from one of the involved research institutions.Here.
Original news story from the Globe and Mail. Here.

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