Atacama Large Millimeter/Submillimeter Array Now being built in the Chilean desert, ALMA will be the world's most advanced radio astronomy observatory (and the highest, at 16,500 feet). Its main array will have 50 movable antennas, each almost 40 feet in diameter, that will act as a single immense telescope. ALMA will allow inspection of radiation from some of the coldest objects in the universe, such as the vast clouds in interstellar space where stars are born. Astrophysicists can use it to probe everything from gas being sucked into black holes to gas erupting from volcanoes on Jupiter's moon Io. Expected completion: 2013.