The hunt for antimatter begins at the space station: Will dilithium be next?
A $2 billion particle detector, newly installed on the International Space Station, begins its search for antimatter, dark matter, quarks, and more.
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Once the device had power, the science team checked out the detector, whose seven individual detector elements are aligned to within 1/10 the width of a human hair. The detectors, along with some 650 microprocessors and some 300,000 data channels, worked perfectly the first time, says Ting.Skip to next paragraph
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While the experiment, 17 years in the making, has a specific research agenda, part of its scientific allure is the potential for uncovering things scientists haven't anticipated – a trait common to other high-energy physics experiments.
Instead of manufacturing its own particles, like an Earthbound detector does, the AMS-2 will record collisions between incoming cosmic rays – essentially the cores of atoms representing a wide range of elements – and its detectors. Many of these particles will collide at energies far higher than any terrestrial physics lab could generate.
Like venerable observatories such as the Hubble Space Telescope, the AMS-2 must operate in space to detect these particles, which Earth's atmosphere absorbs.
With the energies and mass ranges available to study, "we're entering a region nobody's entered before," Ting says. "What we're going to see, nobody knows."
Science objectives include:
- Getting a better handle on the cosmic-ray environment astronauts face as they live and work in space. The spectrometer will be able to measure the incoming particles over a wider range of masses and energies than any predecessor.
- Shedding light on the matter-antimatter mystery. Some researchers have proposed that a process in the early history of the universe tipped the scales in favor of matter – but as researchers have tried to work out the math behind that process, the calculations, in effect, make predictions that don't match astrophysicists' observations.
If the hunt for antimatter – in the form of anti-helium – succeeds, it will yield the first wisp from a smoking gun that anti-matter counterparts to known elements exist outside of a terrestrial laboratory.
A prototype alpha magnetic spectrometer flew aboard a shuttle in 1999. Its results implied that for every million helium nuclei in the universe, there could be no more than one anti-helium nuclei. It's another way of saying: We didn't find any.
The new spectrometer should be able to detect anti-helium at levels of one in a billion helium nuclei.
- Hunting for evidence of dark matter. One candidate is a hypothesized particle dubbed a neutralino. Researchers say if these are out there and colliding, among the collision debris will be electrically charged particles, which the the AMS-2 can detect. Sudden peaks in the number of gamma rays, or in the number of antimatter versions of protons and electrons, would signal interactions between dark-matter particles, according to the AMS-2 team.
- Looking for strange new forms of matter. Crack open a proton or neutron on Earth, and you'll find quarks inside, Ting explains. Physicists have identified six types of quarks. But the protons and neutrons on Earth only use two types, in different combinations. The other four have appeared – fleetingly – in physicists' labs. Some researchers have proposed that protons and neutrons could have variants that use three different types of quarks, but none has yet been found.