It's official: The world's next leading particle accelerator, the Large Hadron Collider straddling the Franco-Swiss border, will not switch on until May 2008, according to a statement Friday from CERN, the European particle physics laboratory. Researchers had planned to perform a test run at the end of the year to work out any kinks in the $10 billion machine—a circular tunnel 27 kilometers (17 miles) in circumference that will operate at temperatures colder than outer space.

In March, one of the collider's superconducting magnets failed a high-pressure test, forcing CERN and Fermi National Accelerator Laboratory, the U.S. lab that had built the magnet, to plan a fix, which is currently underway, the statement says. A number of small delays had already put the planned test run in jeopardy, but the magnet failure finally ruled it out completely. Instead the instrument will be fired up next year at full energy.

Researchers hope the collider will reveal the Higgs boson, the long-sought source of mass for all other particles.