The International Space Station (ISS) is about to make a remarkable series of flybys over the United States. Beginning this 4th of July weekend, the station will appear once, twice, and sometimes three times a day for many days in a row. No matter where you live, you should have at least a few opportunities to see the biggest spaceship ever built.

Check NASA's ISS Tracker for flyby times.

Above: In bright evening twilight, the International Space Station soars over Hawaii's Kilauea Volcano on June 3, 2009. Image credit and copyright: Stephen O'Meara. Used with permission. [larger image]

The ISS has been under construction for nearly 11 years, and it has grown very large and very bright. The station is now more than 350 ft wide (wider than a football field), has 12,600 cubic feet of labs and living quarters, and on Earth would weigh about 670,000 lb. Sunlight illuminating the massive outpost makes it shine fifteen times brighter than Sirius, the brightest star in the sky.

Sometimes it is even brighter than that. Sunlight glinting from the station's flat surfaces (mainly solar arrays) produce dazzling flares as much as six hundred times brighter than Sirius. For astronomers: On the scale of visual magnitudes, space station flares register -8.

"The station flared spectacularly on May 22nd when it passed over my backyard observatory in the Netherlands," reports amateur astronomer Quintus Oostendorp. "I knew the ISS was coming, so I had my telescope ready and I was able see exactly what happened." Click on the image to launch a movie he recorded through his 12-inch Newtonian reflector:

Above: Sunlight glints from the space station's solar arrays on May 22, 2009. Photo credit: Quintus Oostendorp of Vaassen, the Netherlands. [larger still image] [movie]

At present, the flares are unpredictable. No one knows when they will happen or exactly how bright they will be. Any given flyby could be interrupted by one—and that's what makes the watch so much fun.

The marathon of space station flybys won't stop until mid-to-late July (depending on your location). That gives space shuttle Endeavour, currently scheduled to launch on July 11th, time to reach the space station and join the show. As the shuttle approaches station for docking, many observers will witness a memorable double flyby—Endeavour and the ISS sailing side by side across the starry night sky.

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What now? Check for flyby times, ready your telescope (optional), and let the sightings begin.