Ice box

A massive polar detector is being used to explore energy sources in the Milky Way

If you've been out in the wee hours to watch the rise of Matariki, you might have also been awed by our entire galaxy. The Milky Way is best viewed on moonless nights during the winter months, when it can be seen as a hazy band of stars stretching across the night sky.

But now, astronomers have delivered a new map of our galactic home, made not by light but by matter. They used an extraordinary particle catcher buried deep in the ice near the South Pole, known as the IceCube Neutrino Observatory. It is literally a giant ice cube - a cubic kilometre of ice studded with a 3D grid of strings beaded with more than 5000 exquisitely sensitive light detectors ready to catch neutrinos.

Neutrinos are ubiquitous but elusive. Each second, trillions of these ghost-like cosmic messengers hurtle through the Earth, but they remain undetected unless they collide with another particle within this giant frozen detector. "Many neutrinos pass completely unimpeded through the Earth," says Jenni Adams, an astrophysicist at the University of Canterbury and a member of the 350-strong international IceCube collaboration.