KENNEDY SPACE CENTER, Fla. — The astronauts aboard the space shuttle Endeavour attached a $2 billion cosmic ray detector to the International Space Station on Thursday, and delighted scientists immediately began detecting “thousands and thousands” of subatomic particles from deep space.

Equipped with a powerful magnet and an intricate array of sensors, computer processors and high-speed data links, the Alpha Magnetic Spectrometer is designed to measure tiny deflections in the trajectories of cosmic ray particles to look for the tell-tale signs of antimatter and the unseen dark matter believed to make up nearly 25 percent of the universe.

It also will be on the lookout for the unexpected as it sifts through torrents of passing protons, electrons and atomic nuclei for the next 10 years or longer, ideally for the remaining life of the space station.

Within two to three hours, scientists and engineers at the Johnson Space Center in Houston were receiving a steady stream of data. “We have thousands and thousands of particle signatures already,” said Samuel Chao Chung Ting, a Nobel laureate and the project’s principal investigator.

One of the mysteries the device was designed to explore is what happened to the antimatter that must have been created when the universe was born.

In the beginning, Ting said, “You have matter, you must have antimatter; otherwise we would not have come from the vacuum.

“So now the universe is 14 billion years old, you have all of us, made out of matter. The question is, where is the universe made out of antimatter?”