NASA, via Agence France-Presse — Getty Images
A view of the International Space Station from 2011 showing the Alpha Magnetic Spectrometer, the round instrument in the center of the image. Astronomers say the $1.6 billion cosmic ray experiment has provided them with evidence of “new physical phenomena” out in space.
By DENNIS OVERBYE
Published: April 3, 2013
We still don’t know what’s happening on the dark side of the cosmos, but astronomers said Wednesday that they might be on the verge of finally finding out what makes up the mysterious dark matter that gives shape to the visible structures of the universe.
Saying the results represented evidence of “new physical phenomena,” scientists said Wednesday that a $1.6 billion cosmic ray experiment on the International Space Station had confirmed previous reports that local interstellar space is crackling with an unexplained abundance of high energy particles, especially positrons, the antimatter version of the familiar electrons that constitute electricity and chemistry.
Cosmologists have suggested that decaying dark matter particles would produce such a signal, but so could pulsars, the spinning remnants of dead stars that throw off wild winds of radiation. The disappointing news is that even with the new data, physicists can’t tell yet which is the right answer. “I don’t think it makes you believe it must be dark matter, nor do I think it makes you believe it cannot be,” said Neal Weiner, a particle theorist at New York University.
The good news is that the Alpha Magnetic Spectrometer, as the instrument is called, is only two years into what could be a 10-year voyage on the space station, and is working brilliantly. Samuel Ting, the leader of the spectrometer team, which included scientists from 16 countries, said in a statement released from CERN, “Over the coming months, A.M.S. will be able to tell us conclusively whether these positrons are a signal for dark matter, or whether they have some other origin.”
Scientists had been sitting on the edges of their seats since Dr. Ting announced in February that he would be making a report on the space station experiment soon. He reported the first results from his experiment in a lecture at CERN on Wednesday and in a news teleconference hosted by NASA. The group submitted a paper to Physical Review Letters. Astronomers and others from outside the collaboration responded enthusiastically.
“A.M.S. has confirmed with exquisite precision and to high energy one of the most exciting mysteries in astrophysics and particle physics,” said Justin Vandenbroucke, of the University of Wisconsin and Stanford’s SLAC National Accelerator Laboratory.
Maria Spiropulu, a Caltech particle physicist, said, “They have exquisitely small errors and they stop the plot at the cliff hanger so we will be asking for more.”
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