For astronomers, neutrinos are both good news and bad news. The good news is that these particles can reveal details about the objects that created them — stars and exploding stars, for example. The bad news is they’re really, really hard to detect.

Neutrinos are the most common type of normal-matter particle. They’re produced in nuclear reactions — the fusion of hydrogen atoms to make helium, for example. So every single reaction in the heart of the Sun or any Sun-like star produces a neutrino.

What makes neutrinos such good tools for astronomers is that they almost never interact with other matter, so they zip through anything in their path — from the vacuum of space to stars and planets. In fact, trillions of them pass through your body every second. And they’re not deflected by magnetic fields — they fly straight on through space. That makes it easy to track where they came from.

Or it would if they were easy to detect. Since they seldom interact with normal matter, it’s hard to catch them. It takes special detectors, built underground or underwater. And even with almost countless neutrinos passing through it, a detector might catch a single neutrino every few hours or even days.

But scientists want to catch a lot of them because they can reveal details about the reactions that power stars, and about the nature of matter itself. One of the biggest detectors yet is under construction in a gold mine in South Dakota. More about that tomorrow.

Script by Damond Benningfield