Physicists’ quest for some of the most elusive particles, neutrinos, has garnered attention with stunning detectors and ambitious experiments. The antimatter siblings of neutrinos, antineutrinos, don’t get as much attention. But now, with this map showing all the antineutrinos that stream away from the Earth every second, maybe this little particle can get some time in the spotlight.
For Science News, Meghan Rosen reports that more than 10 septillion antineutrinos leave Earth each second. These particles come from the radioactive decay of elements as they break down, so in the map, nuclear reactors show up as dark red "hotspots" of antineutrino activity. On the map the Himalayas appear hot. The Earth’s crust beneath those highest mountain peaks, it turns out, is rich in radioactive elements.
Researchers published the map in Scientific Reports.
The map is more than just a pretty picture. Scientists hope that by keeping an eye on the streaming antineutrinos, they may be able to monitor reactors around the the world, reports Prachi Patel for IEEE Spectrum. Patel writes that the challenge, just as it is with the neutrino, is detecting these light particles.
Only one in 100 billion passing through matter interact with it. Today’s detectors capture the particles using gadolinium-spiked water or solvent inside tanks several meters on a side. In the tanks, an antineutrino occasionally collides with protons in the liquid, creating a neutron and a positron. Photodetectors sense light flashes produced when the positron crashes into an electron and when the neutron is captured by the gadolinium.
The large tank of liquid must be put underground to block out cosmic rays that can lead to false positives, and that can be a problem.
Rosen points out that the dark blue of the deep oceans on the map indicates very little antineutrino activity and therefore an ideal place to build a very sensitive detector.