Dark Matter Seen

 

The simplest description of dark matter is matter that doesn’t interact with light. It also doesn’t directly interact with any atoms, which makes it almost impossible to observe. Only using sophisticated gravitational detection techniques, based on one of Sir Isaac Newton’s laws, seems to work. And until recently even that kept coming up empty yet there is so much of it out there. Scientists believe dark matter is an invisible form of matter that outweighs ordinary matter in the universe by more than 5 to 1. 
Last week the first results from the Alpha Magnetic Spectrometer were announced at the European nuclear agency CERN. After looking at 25 billion cosmic ray events over 18 months, scientists think they have seen the first hints of dark matter. But it will take months to sort out the data to make sure there is no other explanation first.
 
Nobel Prize-winning MIT physicist and lead scientist on the AMS Sam Ting says, “All evidence supports the existence of dark matter but I cannot rule out that the origin comes from pulsars.” He says he is confident that with enough time science will be able to answer the question.
AMS improved the precision of earlier data (which it also confirmed). It detected particles at higher energies than previous instruments and most critically it found that the particles hit the detector in equal amounts from all directions.
The dark matter detector sits on the outside of the International Space Station and it senses positrons, which particle physicists believe result after dark matter particles annihilate after coming into contact with other dark matter. But positrons can also come from radiation in a nearby neutron star and other sources. So before the science team makes an official pronouncement about the discovery of dark matter they want to make sure that’s what they’ve found.
The AMS collects and identifies charged cosmic rays, looking for signs of dark matter. This near-Earth experiment is the most powerful and sensitive particle physics spectrometer ever deployed in space. It is also the most expensive, costing about $2 billion. But if it’s found dark matter then that easily justifies the big price tag for knowing more about the makeup of the universe. The AMS is mounted on the outside of the space station because dark matter gets absorbed by Earth’s atmosphere, making it impossible to study.
Dark matter is believed to be the glue that holds galaxies together. Scientists now believe dark matter comprises about 26.8 percent of the universe compared to the 4 percent that scientists think is ordinary matter including people, planets and stars. Scientists are still trying to figure out the particles that make up dark matter. The remaining 70 percent of the cosmos is thought to consist of dark energy, an even bigger enigma than dark matter, which appears to be driving galaxies apart at an ever accelerating rate.
During the captured cosmic ray events the AMS detected about 400,000 positrons, the antimatter partner particles of electrons. A statement from CERN says that is the largest number of energetic antimatter particles directly measured and analyzed from space.