Sky Lights

What's that light in the western sky? Hint: It's not ET

By Bob Berman|Thursday, March 01, 2001

The mystery light that inspires the most reports of "unidentified flying objects" is now floating in the western sky at dusk. There is actually no mystery— it's Venus. But Earth's nearest neighbor is so brilliant that it regularly prompts anxious calls to the local observatory. And Venus is not the only celestial object misidentified time and again. So before you jump to the conclusion that you've spotted a UFO, run through the following questions: Do you see the object through glass, such as a car's windshield? A simple reflection often solves the mystery.

Does the object have shape? A point of light in the sky could be anything. On the other hand, a bona fide spacecraft should reveal some distinctive features, especially if it hovers close enough for the crew to invite you in for tea and a standard tour of the ship before probing your internal organs.

If the unidentified object is a point of light, does it really move? Look carefully. Passing clouds can make a fixed light seem to be in motion. One upstate New York astronomer recently witnessed a group of cars parked by a cornfield, where several people were staring intently upward at a strange flying light. The light turned out to be Jupiter; fast-blowing clouds created the illusion that it was changing position.

If the point of light is stationary, does it flicker and change color? People sometimes think "UFO" when they see the rising or setting of the night's brightest star, Sirius. It normally appears a steady blue-white, but when Sirius sits close to the horizon, its light is refracted by a long passage through Earth's atmosphere. Like a prism, the air splits up the starlight into a kaleidoscope of vivid colors. If the unidentified light in the sky shines brighter than any star, it's probably a planet.

If the light moves, does it follow a slow and steady path? Then you've most likely spotted a satellite. Satellites often change brightness dramatically as they orbit, because of their uneven shape or because of sunlight glinting off their solar panels. They may suddenly wink out when they pass into Earth's shadow. And small muscle movements in the eyes can make them appear to zig and zag. The huge International Space Station passes prominently through the heavens a few times a week. Like virtually every other satellite, it can move in any direction except westward. A brilliant, slow-moving white light or a formation of two or three— especially low in the sky— is usually caused by landing lights from aircraft headed in your direction. They can remain nearly stationary, persist for several minutes, and appear yellow or orange due to light absorption by the intervening air.

Does the light follow a rapid, straight line and vanish within seconds? If so, it is undoubtedly a meteor, a fleck of space rock glowing white-hot as it races through the upper atmosphere. In the process, meteors may produce exciting surges of brightness and may even explode. A meteor bright enough to cast shadows is called a fireball; one that blows itself to bits is known as a bolide.

Does the light follow long circles or zigzags in an overcast sky? Searchlights illuminating the bases of clouds can produce this spooky effect.

Ninety-five times out of a hundred, asking these basic questions will probably turn your UFO into something wholly identifiable— call it an IFO.

The sci.skeptics newsgroup has a handy guide to many of the more exotic UFO claims ( Of course, the best way to avoid being fooled is to keep up with the changes in the sky. Sky & Telescope's "sights" page ( is a good place to start.
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