Where do cosmic rays come from? That's something that has long puzzled scientists. Now, though, a new study has revealed that most of the cosmic rays that we detect may have originated relatively recently from nearby clusters of massive stars.
Cosmic rays are actually high-speed atomic nuclei with a wide range of energy. The most powerful cosmic rays actually race at the speed of light. Earth's atmosphere mostly shields us from these cosmic rays. However, cosmic rays can potentially be hazardous to astronauts traveling through space. With missions that are scheduled to send humans to Mars, it's especially important to note the effects of cosmic rays and find out the best ways to help shield astronauts from them.
Cosmic rays themselves are actually created through several different violent events that occur in space. Some come from explosive events on the sun, such as solar flares and coronal mass ejections. Others come from massive black holes at the centers of other galaxies.
In order to better study cosmic rays, researchers relied on results from NASA's Advanced Composition Explorer (ACE) spacecraft. The ACE actually allowed researchers to estimate the age of the cosmic rays, as well as the distance to their source.
"Our detection of radioactive cosmic-ray iron nuclei is a smoking gun indicating that there has likely been more than one supernova in the last few million years in our neighborhood of the galaxy," said Robert Binns of Washington University and lead author of the study.
Eric Christian of NASA's Goddard Flight Space Center noted that ACE actually detected about 300,000 galactic cosmic rays of ordinary iron, but just 15 of radioactive Iron-60. The presence of Iron-60 in general means that the cosmic rays must have been created relatively recently, he added.
It's likely that these cosmic rays were created by clusters of massive stars within a few light-years of our own galaxy.
The findings reveal a bit more about cosmic rays. More specifically, they show where cosmic rays in our own galaxy likely came from in the first place. This is important moving forward to understand what areas of space may receive more impacts from cosmic rays.
To find out more about NASA's ACE program, visit NASA's website.
