Astrophotography

Astronauts onboard the International Space Station are capturing some amazing photos of the night sky.

It's a weird place for an astronomer. Meteors fly underfoot. Auroras appear just inches in front of your nose. City lights twinkle, but stars don't.

Astronaut Don Pettit loves every minute of it.

"There's always something good to see out the window of the space station," says Pettit, who happens to be an amateur astronomer as well as the science officer of the International Space Station (ISS).

"Lately we've been having some extraordinary auroras," he reports. "They meander like big green amoebas crawling across the sky. Sometimes there is a faint touch of red layered above the green. These lights are constantly changing. They swirl. Bright spots come and go. Green blobs transform into upward-directed rays topped by red feathery structures."

Long before he went to live onboard the space station, Pettit was an avid aurora watcher. "I've taken photos of the Northern Lights from Alaska and Canada," he says. Some of those displays were magnificent, but "the view from the station is even better."

Auroras are caused by electrons and protons from space raining down on Earth's atmosphere. The solar wind, through a set of complex and fascinating interactions with the Earth's magnetic field, is the ultimate source of energy that drives these particles toward our planet. When they hit the top of the atmosphere, they excite atoms and molecules and make the air glow. Reds and greens come from atomic oxygen, blues from nitrogen.

more Astronaut Don Pettit, Expedition Six ISS science officer, takes pictures of Earth through a window in the Destiny laboratory on the International Space Station (ISS)

These colourful lights range in altitude from 80 km to 500 km above Earth's surface. The ISS orbits our planet about 400 km high, so the space station can actually fly through auroras. There's no danger to astronauts, though. The aurora-causing electrons and protons are thousands of times less powerful than potentially hazardous cosmic rays.

"Last January 2002 we flew through an auroral curtain over Canada," recalls Pettit. The station was surrounded by a dimly glowing red fog. Just below were green rivers of light. "It was like I had been shrunk down to some miniature dimension and inserted into a tube of a neon sign. And it was just on the other side of the window pane. I wanted to reach out and touch, but of course I couldn't."