Scientists Are Hunting for ‘Ghost’ Particles from Space Under the South Pole

Deep under the ice of the South Pole, an observatory made of thousands of threaded sensors is hunting for ghostly particles called neutrinos, which are forged by some of the most energetic processes in the universe.

Since it first began operations a decade ago, the IceCube Neutrino Observatory has captured dozens of neutrinos created in explosive events such as supernovae or radiant eruptions driven by supermassive black holes. As the biggest neutrino detector in the world, IceCube has opened a new window into the high-energy universe and the bombastic events that occur in it.

In an episode of Motherboard’s Space Show posted on Wednesday, IceCube collaboration members Marcos Santander and Lu Lu explained why snagging these particles is so important—and why they’re so difficult to detect, despite their ubiquity.

“We have about 100 billion neutrinos crossing every square centimeter of our bodies each second,” said Santander, an assistant professor of physics at the University of Alabama. “Over the course of a lifetime, you have about 10^20 neutrinos going through your body,” he added, “which is about 100 times more particles than there are grains of sand on Earth.”

As to why they are so tricky to capture, the “short answer is that neutrinos are small, light, and super-antisocial,” added Lu, an assistant professor of physics at the University of Wisconsin-Madison. “Neutrinos don't carry an electric charge, so that means they are not interacting with photons or electromagnetic forces, and they have a very small mass, so they are not interacting so much with gravity either.” 

IceCube overcomes these challenges by distributing long strings of sensors more than a mile beneath the South Pole. The placement of these sensors within extremely clear glacial ice allows the collaboration to capture the minute disruptions of matter that neutrons can produce as they pass through the quiet environment.

The observatory has shed light on the core of our own planet and traced neutrinos back to cosmic blowups that occurred four billion light years away, among many other discoveries. But it’s work is far from finished, and new upgrades will make the detector even more sensitive in the 2030s. To learn more about IceCube, its achievements, and whether it has any affiliation with the rapper of the same name, check out the new episode.