After a 2-billion-kilometer journey that began in September 2016, NASA's OSIRS-REx spacecraft has safely arrived at asteroid Bennu. At 17:00 UTC, with the spacecraft just 20 kilometers away from its 500-meter-wide target asteroid, OSIRIS-REx lit its engines for a 20-second burn that put it on course for an initial close flyby of Bennu's north pole tomorrow.

"We know the burn is occurring," said Javi Cerna, an OSIRIS-REx telecom engineer, during a NASA TV broadcast from Lockheed Martin in Littleton, Colorado. Cerna watched his computer screen closely as the spacecraft's radio frequency shifted, indicating a change in velocity. "We have arrived!" he called out moments later.

Back at the University of Arizona, which is leading the mission, a crowd watching at the Stevie Eller Dance Theater broke into cheers. Dante Lauretta, the mission's principal investigator, told reporters later that the burn appeared to have gone well, but he was eager to read the navigation report, which was probably waiting in his inbox.

"As soon as we're done here, I want to get to my office and get back to work," he said.