Mauna Kea in Hawaii has beaten off competition from Cerro Armazones, in Chile's Atacama desert, to host the Thirty Meter Telescope. Henry Yang, chancellor of the University of California, Santa Barbara, and chair of the telescope's board of directors, announced the winning site on 21 July. The decision has been two years in the making, he said.

Mauna Kea, which already hosts many other telescopes, was picked over its Chilean rival for its superior observing climate. It is higher and drier, has less atmospheric turbulence, and its average temperature fluctuates less through the year and over a day, notes board member Richard Ellis of the California Institute of Technology in Pasadena.

Construction of the telescope, which will cost around US$1 billion, is scheduled to begin in 2011 and end in 2018.