A Flash In The Night


(Two meteors during the 2001 Leonid meteor shower — Bob King/ News Tribune)

Susan of Virginia, Minn. wrote me the other day about something that really caught her attention. In her words: "I was on Highway 33 on Friday, Feb. 15th. I’m not sure what time it was, maybe 9 or 9:30 and to our east, a huge green ball/star/meteor/ufo fell from the sky into the woods. Another friend driving ahead of us saw it as well."

Susan, my first thought was aliens because of the green color but then logic grabbed hold. By the way, how did we humans decide on green as the preferred color of extraterrestrials? Do we secretly envy plants and their ability to use sunlight to make energy?

Of course what Susan saw was an especially bright meteor. It’s not uncommon for them to be green but sometimes you’ll also see red, orange or blue colored ones too. The colors arise from materials on the meteorite’s surface heated by friction as well as interactions with our atmosphere. Each time you see a "shooting star", you’re witnessing the burn up of a small fragment of ice or rock ejected long ago by an asteroid breakup or a comet. The Earth plows into these bits the way you plow into bugs on a summer’s night in your car. Most are no bigger than a sunflower seed, but when they strike the rarefied air overhead at 25,000 to 150,000 mph, they vaporize in a glorious flash.

Meteors often seem very close because we don’t have any good comparisons for distance. It may look like that big ball of fire landed in the field nearby but because meteors burn up 60 miles overhead, almost all of them are really very far away. Even if one is large enough to survive the fiery plunge, the atmosphere puts the brakes on so quickly that the meteorite is "dark" during the last 15 miles of its journey to the ground.  

 Bright meteors aren’t limited to meteor showers and can happen at any time of year. That’s why it’s always worth your while to look up.