Humans are always asking questions and looking for answers. Important findings from a cosmic ray detector sent into space in 2011 suggest a possible answer to one of humanity’s biggest questions—what makes up the universe?
The $2 billion cosmic ray detector aboard the International Space Station discovered something that could be "dark matter," a mysterious substance believed not only to hold our universe together but also to make up a quarter of it. Understanding dark matter means understanding more about the cosmos, including its composition. Dark matter does not give off light, nor can it absorb light, so it has never been directly observed. Therefore, scientists know very little about it.
The cosmic ray detector, or the Alpha Magnetic Spectrometer (AMS), weighs seven tons and has a three-foot magnetic ring at its core. The detector transmits data to the European Organization for Nuclear Research, also known as CERN, which is located on the Swiss-French border in Geneva. There, a team of 600 scientists led by famous MIT physicist Samuel Ting analyzes the data.
While the data the AMS collected could be related to dark matter, scientists originally thought that it was energy coming from pulsars, the extremely dense remnants of dead stars. The data shows an excess of positrons, or positively charged subatomic particles. The theory that dark matter is responsible for the change in positrons was supported by data collected in 2014. The effect that dark matter has on positrons is unlike that of pulsars. According to the data, when affected, the positrons climbed at a steady rate without any sudden rises or dips. Had any been present, that would indicate that a pulsar or some other source was the cause of the excess positrons.
Since it was launched, the AMS has found more than 400,000 positrons that may have been emerged when particles of dark matter collided and destroyed each other. The AMS has also recorded data from 54 billion cosmic events, 41 billion of which have been analyzed by scientists.
Initially, Ting's scientists thought that the ratio of electrons and positrons dropped when a high amount of energy was present. In 2013, however, results showed the exact opposite—the ratio of positrons to electrons climbed when energy reached a range of eight billion to 275 billion electronvolts. Further, in 2014, scientists found that the proportion of positrons started to decrease when energy reached around 275 electronvolts.
This is significant because knowing the range at which positrons and electrons are affected by dark matter allows scientists to calculate the mass of the particles. They are able to do so because of the relationship between energy and particle mass. Also, because each particle has different physical properties, determining mass will enable scientists to identify these elusive dark matter particles precisely.
Ting states that in a few years, additional statistics could offer the information that scientists still need. The AMS will continue its search for dark matter and antimatter for at least another five years, so Ting's remaining questions could soon be answered.
[Sources: Associated Press; Wisconsin State Journal; nasa.gov]