NASA's Juno spacecraft has successfully entered orbit around Jupiter. At 8:53 P.M. Pacific time, ground controllers received a telemetry tone of 2,327 hertz -- equivalent to the highest D note on a piano keyboard—indicating that Juno's 35-minute engine burn had slowed the spacecraft enough to slip into the giant planet’s gravitational embrace. Launched in 2011 on a nearly five-year interplanetary voyage, Juno is only the second spacecraft to ever orbit Jupiter, after the Galileo mission that explored the giant planet from 1995 to 2003. During its capture into orbit Juno passed just 4,490 kilometers above the Jovian cloud tops, so close that the planet filled half its sky. Even so, Jupiter is so immense that an astronaut riding along would have seen only about 5 percent of the planet’s cloud-shrouded face.

At 9:50 P.M., the maneuver was officially complete as the spacecraft turned its solar arrays back toward the sun. “I won't exhale until we’re sun-pointed again,” Juno's principal investigator Scott Bolton had said at a press conference earlier in the day.

The spacecraft plummeted in from interplanetary space over Jupiter's north pole at about 7:30 P.M., falling ever faster as it plunged deeper into the planet’s gravitational field. Just two days ago its speed relative to Jupiter was nine kilometers per second; midday yesterday, 12 kilometers per second; and by the rocket burn, 54 kilometers per second. The burn reduced its speed by just 1 percent, but that was enough. (Theoretically, the spacecraft was captured by the planet at 8:38 P.M., about halfway through the burn, but confirmation did not come until later.) After skimming so close to Jupiter's upper atmosphere, the spacecraft soared back up from the planet’s cloud tops at about 9:30 P.M. into a looping, elongated orbit out to 8.1 million kilometers.