The Sudbury Neutrino Observatory (SNO) is a neutrino

Neutrino

A neutrino is an electrically neutral, weakly interacting elementary subatomic particle with a half-integer spin, chirality and a disputed but small non-zero mass. It is able to pass through ordinary matter almost unaffected...

 observatory located 6,800 feet (about 2 km) underground in Vale Inco's Creighton Mine

Creighton Mine

Creighton Mine is an underground nickel mine, owned and operated by Vale Inco Limited in the city of Greater Sudbury, Ontario, Canada...

 in Sudbury, Ontario

Ontario

Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

, Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

. The detector was designed to detect solar neutrino

Solar neutrino

Electron neutrinos are produced in the Sun as a product of nuclear fusion. By far the largest fraction of neutrinos passing through the Earth are Solar neutrinos....

s through their interactions with a large tank of heavy water

Heavy water

Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...

. The detector turned on in May 1999, and was turned off on 28 November 2006. While new data is no longer being taken the SNO collaboration will continue to analyze the data taken during that period for the next several years.