Tuesday, May 27, 2003

Strange Lights on Summer Nights

Strange Lights on Summer Nights
by Dave Adalian

Summer is my favorite time of year. Nights are warm, and the starry sky is full of wandering lights--mysterious beacons in the sky. X-Files stuff.

OK, so these aren’t aliens coming to meet and eat mankind. But they are spacecraft. And they are watching us. The guys at the controls, though, are here on Earth and as human as you and me.

Until 1957, Earth had only one satellite, the Moon. In that year the Soviet Union launched Sputnik and since then some 27,000 manmade objects have been cataloged in the sky. About 9,000 or so are still in orbit, and a few hundred of them can be viewed with the naked eye.
This is the best time of year to see them. Earth’s seasons are caused by our planet’s tilt. When our hemisphere leans toward the Sun, the weather warms into summer. This slant makes Earth’s shadow fall low in the sky a few hours after sunset and before sunrise, leaving satellites exposed to the light and easy to see.

The only thing you need for satellite hunting is a dark, clear, moon-less sky like those we’ll have this weekend. The darker the sky, the better the hunting, but around here the backyard will do fine. What I like to do is lie back--in the swimming pool if it’s warm enough--let my eyes adjust to the dark, then wait until I see a star that’s come loose from its moorings drifting slowly across the sky before fading into Earth’s shadow. This time of year, I can easily catch a dozen or more roving lights before midnight, when Earth’s shadow grows tall.

Mostly, the lights are dim but steady points, like stars sailing slowly across the night. But, some are different. Iridium satellites, a group of communication repeaters, can flare up unexpectedly, quickly becoming the brightest thing in the sky before disappearing just as fast. Others flash on and off as they tumble through the sky. Mostly, these are old, dead machines falling uncontrolled through space.

One of the brightest satellites is the International Space Station. It appears regularly over the Valley, and you can find a schedule of its passes--and the passes of dozens of other manmade moons--at Heavens-Above.com. There you’ll find maps, instructions on how to use them and some details about what you’re seeing. You can also use the service to look up previous sightings.

Happy hunting!


This column originally appeared in the Visalia (Calif.) Times-Delta on May 27, 2003.