PAMELA stands for Payload for Antimatter Exploration and Light-nuclei Astrophysics, and the satellite-based experiment was launched in 2006 for the purpose of studying cosmic rays, high-energy subatomic particles that are slamming into the Earth's atmosphere constantly, creating showers of "daughter" particles in the process. That's right, Nature is running her very own particle accelerator experiment at the edge of Earth's atmosphere.
That means that the showers of daughter particles should include small amounts of antiprotons, just like in manmade particle accelerators. Most of those would annihilate the moment they came into contact with their ordinary matter counterparts, but astrophysicists have long hypothesized that a few remaining antiprotons could become trapped within the Earth's magnetic field, resulting in "an antiproton radiation belt" similar to the Van Allen radiation belts that already exist.
That's what PAMELA scientists think they've found, nestled within the Van Allen belts -- specifically, a region called the South Atlantic Anomaly. There's so many high energy particles trapped in this region, the Hubble Space Telescope needs to switch off whenever it passes through several times a day. So it seemed like the best place to look for elusive antiprotons.
"Trapped antiprotons can be lost in the interactions with atmospheric constituents, especially at low altitudes where the annihilation becomes the main loss mechanism," study co-author Alessandro Bruno of the University of Bari told BBC News. "Above altitudes of several hundred kilometers, the loss rate is significantly lower, allowing a large supply of antiprotons to be produced."
PAMELA scientists analyzed 850 days worth of data, focusing on those periods when the satellite was in the anomalous region. And lo and behold, they detected a small amount of antiprotons trapped in the Van Allen belts. We do mean "small": 28 antiprotons. It's still roughly three times more than one would expect to find from the solar wind, so it seems as if the hypothesis is correct.
And that, in turn, might shed light on one of the foremost mysteries in modern cosmology: what gave rise to the matter/antimatter asymmetry in the earliest moments of our universe that gave us the matter-based cosmos we know and love?
Interesting and noteworthy for physicists, sure, but is it especially exciting otherwise? I wondered, until I read the fourth sentence in the BBC News story about the paper: "The researchers say there may be enough to implement a scheme using antimatter to fuel future spacecraft."
Talk about burying your lede! But I'll go ahead and be the wet blanket here and point out that this is a pretty optimistic interpretation of "the most abundant source of antiprotons near the Earth." We're talking about exactly 28 antiprotons, here.
I get it: everyone loves Star Trek, and geeks around the world still dream of one day being able to harness the power of antimatter to fuel their very own version of the USS Enterprise, which relies on large quantities of the stuff to supply sufficient propulsion to boost the starship into its famous "warp drive."
As he did with many technical aspects of the series, for the Enterprise propulsion system, creator Gene Roddenberry drew on established scientific fact. The concept of matter/antimatter propulsion is not just the stuff of science fiction.
Read more at Discovery News
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