Space Station Supernova

Next week, sky watchers in many US cities can see the space station materialize like a supernova in the early morning sky before sunrise.

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August 28, 2002: The International Space Station (ISS) had just swung around the night side of Earth when astronaut Peggy Whitson looked out the window. The planet below was dark, but Earth's limb was glowing. "It was a thin, bright band of light--at first a deep royal blue, followed by the addition of red and orange," she recalled. "The rays of light seemed to be wrapping their fingers around the planet."

Whitson narrowed her eyes when the Sun finally popped over the distant horizon. It was awfully bright. The station itself, moments earlier dark except for a few glowing windows, lit up from stem to stern reflecting the intense sunshine.

What a sunrise!

Right: Astronauts onboard the space shuttle Atlantis captured this picture of a sunrise from low-Earth orbit on May 29, 2000. [more]

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A few hundred kilometers below the space station, sky watchers on Earth saw something nearly as wonderful: a bright star materializing like a supernova in the predawn sky. That's what the ISS looks like (from the ground) when it's hit by rays from the morning Sun. It happens often enough, but most people have never seen it because they don't know when to look.

The first week of Sept. is a good time to try. That's when the ISS will fly over several major US cities before dawn, and if you're outside at the right moment you can spot a "space station supernova." You'll have to wake up early, around 5 o'clock in the morning. At first the starry predawn sky will seem ordinary. The horizon will glow a bit (a hint of the rising Sun) and the yellow-planet Saturn might catch your eye halfway up the eastern sky. Then the space station will appear, gliding eastward into the sunlight high above Earth. It will surge in brightness until it rivals or outshines every other star in the sky.

The apparition might remind some onlookers of a Hollywood UFO--and indeed, it is a spaceship, but the explorers inside are human, not aliens. Onboard now are American Peggy Whitson and Russians Valery Korzun and Sergei Treschev. If one of them happens to be looking out the window when the space station materializes above you, you know what they'll be seeing: a gorgeous sunrise.

Above: Local times in September when the ISS will materialize over some US cities. The station will appear at the elevation and compass direction tabulated in the 4th column, then glide toward the northeast horizon. Click on the name of the constellation to see a sky map labeled with the station's path among the stars, courtesy of Heavens Above.

The table above lists ten US cities where the space station will appear in September. Even if your hometown is not included, you might still be able to see the ISS. Find out by visiting one of these three popular web sites: Chris Peat's Heavens Above, Science@NASA's J-Pass or NASA's SkyWatch. Each will ask for your zip code or city, and respond with a list of suggested spotting times and directions. Supernova-style apparitions are those that begin high in the sky, at least 45 degrees above the horizon, just before local dawn. Predictions computed a few days ahead of time are usually accurate within a few minutes. However, they can change due to the slow decay of the space station's orbit and periodic reboosts to higher altitude. Check frequently for updates.

Sky watchers who see the ISS for the first time often remark that the station seems slow--much slower than meteors they've seen. In fact, the station moves rapidly. It circles our planet 16 times per day traveling about 17,000 mph. But that is slow compared to a typical meteor, which travels 100,000 mph and streaks across the sky in seconds.

Right: It is possible to see the ISS through a telescope and record it. This movie was captured by amateur astronomer Ulrich Beinert. [more]

In this case, slow is good. Because the ISS takes minutes to glide from horizon to horizon, it is possible (with practice) to train a telescope on the station and track it. "I have viewed the ISS with an 8" telescope," says amateur astronomer Ulrich Beinert. "Even though it was hard to see details, the station's T-shape was clearly visible. The colors were so vivid; the body of the station glowed bright white, while the solar panels shone in an eerie copper light--amazing!"

You won't be able to pick out the station's tiny windows using an amateur telescope, but you can imagine what they frame: The face of an astronaut--Peggy Whitson, perhaps--staring outward. Colorful rays of light wrapping around the planet. The sudden surge of the rising Sun and then, on the Earth below, a "space station supernova." Set your alarm; it's worth waking up for....

Editor's note: Peggy Whitson is a member of the space station's Expedition Five crew. Her description of sunrise from Earth orbit is reproduced from one of a series of charming letters from space.

NASA's Human Spaceflight -- (SpaceFlight.nasa.gov) Up-to-date information about the space shuttle and the International Space Station.

Track the ISS: Any of these web sites will tell you when and where to look for the space station: Heavens Above (external site); J-Pass; SkyWatch (NASA). Supernova-style apparitions are those that begin just before dawn high in the sky, at least 45 degrees above the horizon. Ordinary horizon-to-horizon passes are beautiful, too, but not the same.

What makes the ISS shine? There are no bright lights on the outside of the space station. The ISS shines by reflecting sunlight, as much as 90% of the light that hits it. Much of the ship is light-colored. Even the awesome solar arrays, which must absorb sunlight to power the station, aren't completely black. Their reflectivity is near 35%.

Right: The brightly-lit International Space Station in April 2002. [more]

More Spaceship Sightings -- (Science@NASA) The International Space Station is easy to see with the unaided eye. It looks even better through a telescope.

Watch Out for Spaceships -- (Science@NASA) If your neighbors hear you say this, they might laugh at you. But it's true: This is a good week to stand in your backyard and watch spaceships go by.