The wings stretched more than 240 feet, a glistening golden hue in the sunlight and a dazzling sight for the astronauts and everyone else involved.
"It's just really amazing," said Mike Fincke, the space station's skipper. He said there was "a shout of triumph" aboard the linked station-shuttle complex once the two wings were fully extended.
At Mission Control, flight controllers burst into applause. Some engineers were in tears.
"It was just really like a great weight had lifted," said flight director Kwatsi Alibaruho.
The work was a highlight of shuttle Discovery's mission. Completed 220 miles above Earth, the new panels are the final pair of electricity-generating wings and should boost the amount of science research at the orbiting outpost.
The drama unfolded the day after these last two solar wings were hooked up to the orbiting complex.
Right on cue, astronaut John Phillips pushed the button that commanded the first wing to start unfurling. It slowly stretched out like a folded-up map. When the wing was halfway open, Phillips stopped the motion for nearly an hour so the panels could soak up sunlight and be less likely to stick.
The second wing, which had been boxed up for eight years, opened just as easily. A slight crinkle was spotted near the bottom, but flattened when the wing was stretched out.
Most if not all the astronauts watched the wings unfold, peering out windows and through camera lenses, ready to hit the "abort" button in case of trouble.
Flight controllers as well as managers anxiously monitored everything, given the past problems. The last time a solar wing was unfurled in 2007, it caught on a guide wire and ripped. Emergency spacewalking repairs were needed to fix it.
"We learned from that and made it very smoothly," Fincke said.
After 10 years of assembly, the space station now has eight full wings. Altogether, the wings will be capable of generating enough electrical power for about 42 large houses, according to NASA.
On Thursday, a pair of spacewalking astronauts hooked up the $300 million framework that holds the wings. This last major American-made addition increased the mass of the space station to 670,000 pounds; it is now 81 percent complete. Construction is scheduled to wrap up next year with the retirement of NASA's shuttles.
The second of three planned spacewalks will take place Saturday. Also, astronauts inside will test a new processor that converts urine into drinking water. The processor was delivered by the shuttle to replace a broken one and was being installed Friday evening.
Discovery is due to leave the space station Wednesday, carrying back five months' worth of science samples. The hatches between the spacecraft will remain open longer than planned to keep those samples in the station freezer as long as possible. Landing remains scheduled for March 28.
