Astrophysics Underground

Dr Alec Habig has a strange job. Sure, he may hold the prestigious position of Professor in the Department of Physics and Astronomy at the University of Minnesota Duluth, but while most astrophysicists spend their lives in front of computer screens, in labs, in offices or looking up at the galaxy through the lens of a telescope, Dr Habig travels deep into the heart of a State Park, puts on a hardhat, gets in an old mine-shaft elevator, and begins his descent into a state-of-the-art astrophysics facility located nearly a kilometre underground.

Dr Alec Habig is the Associate Director of the Soudan Mine Underground Laboratory, a particle physics laboratory located over 700 metres underground in the oldest iron ore mine in Minnesota.

From 1882 to 1962, the Soudan Underground Mine served as the deepest and richest iron ore mine in the state, but today sees only the tireless work of physicists trying to answer fundamental questions about the nature of the universe.

Dr Habig is one scientist working on the Main Injector Neutrino Oscillation Search (MINOS), an experiment focused on uncovering more about the poorly understood particles called neutrinos.

“Neutrinos are the second most common particle in the universe (after photons of light),” Dr Habig explains, “There are a billion neutrinos for each one of the more ordinary particles you could name (electrons, protons, neutrons). Even though each neutrino is quite light, there’s as much mass in all the neutrinos out there as is in all the luminous matter you look up into the night sky and see (stars, planets, etc). But, we’ve only just started to understand them in the last decade, and still have a long way to go.”

In the MINOS experiment, neutrinos are produced by a particle accelerator at the Fermi National Accelerator Laboratory near Chicago and directed in a beam, straight through the earth, and received 735 kilometres away by the Minnesota lab.

The MINOS experiment started detecting neutrinos from the Neutrinos at the Main Injector (NuMI) beam from the distant Fermi Lab in 2005.

The dense rock walls of the Soudan Underground lab block cosmic rays from interfering with the sensitive experiments.

More than a trillion neutrinos pass through the MINOS detector each year, but only about 1,500 collide with atoms inside the detector, while the majority pass through undetected.
MINOS aims to answer the most fundamental questions about these tiny, baffling particles, such as: Where do neutrinos come from? What is their mass? How are neutrinos related to the mysterious dark matter that makes up nearly a quarter of the universe?

After a decade of MINOS operations, the experiment is wrapping up. “We have more firmly established that anti-neutrinos behave very much the same as regular neutrinos – something which was part of the theoretical predictions, but not well tested till recently,” says Dr Habig.