Astro Bob blog: Fireball over Duluth!There were numerous reports of a bright, flaming object that fell over the harbor last night. Find out more here.
By: Bob King, Duluth News Tribune
Fireball over Duluth!
A bright meteor blazes across the Bowl of the Big Dipper several years back. Photo: Bob King
Were you one of the lucky ones to see the brilliant, flaming object plunge over the region about 7:15 p.m. last night? People all the way from Cook County along Lake Superior's North Shore to Duluth to the Spooner area in northern Wisconsin all reported seeing what appears to be the same object. Audrey Monicken, who lives on Park Point, said she was watching TV when she caught the sight.
"I saw a flaming thing come down out of the sky," she said, and described the object as about the size of a mattress with red flames. From her vantage point, Monicken said the object seemed to disappear in the middle of the bay.
Then we have this description from Wendy Hamm:
"My daughter and I were driving across the Bong Bridge (heading to Superior) when we saw the object in the sky which was on its way down (large, green with red on the bottom and the size of an average round dinner table). It appeared to land in the water/ice in between the Bong Bridge and railroad bridge or possibly where the old Arrowhead Bridge was located. Someone might want to check that area out. And I thought objects from space always landed in the ocean!!"
Brad Wick with the Duluth Police Department checked with the Duluth International Airport in case the object was a plane in distress, but no planes were in the area at the time. So what was it? The most likely explanation is a brilliant meteor called a fireball. In a lifetime you might see a half dozen of these spectacular sights, but they occur somewhere over Earth every day and night.
Every meteor or "shooting star" you see is a fragment of a comet or asteroid. The small ones might only be the size of grain of sand, but the larger ones like last night's can range from pebble-sized to many meters. While still in outer space, fragments destined to become a meteors are called meteoroids. When they enter Earth's atmosphere at speeds from 25,000 to 160,000 mph, they vaporize in a bright flash, creating a brilliant trail we see as a meteor. Because they're so bright and with no ready clues to their true distance, we're usually tricked into thinking meteors are very close by. If one happens to fade out over your downtown you might think it fell on Main Street. In reality meteors burn up some 70 miles over our heads -- and that's if you see one straight up at the top of the sky. If you're watching a fireball off in one direction or another, you have to add in the horizontal distance between you and the object. A more typical distance between you and a bright meteor would be closer to a hundred miles or more.
The outer layer of most meteorites is melted during atmospheric entry and converted to a black "fusion crust" like this stony meteorite displays. Photo: Bob King
If a meteor is large enough to survive the friction and pressure of atmospheric entry and lands in pieces on the ground it's called a meteorite. A meteor destined to become a meteorite usually fades out about 30 miles above the ground and continues in "dark fall" until it strikes the ground. The larger the object falling, the more likely it will create a sonic boom or rumblings like cannon fire on its way down. Did anyone out there hear anything at the time? Could fragments have reached the ground? Unless someone actually sees and hears the objects falling nearby, chances are that this meteor -- if it did produce meteorites -- will be extremely difficult to find. Most fireballs produce a great show but vaporize to dust. Given the vast surface area of the Earth, meteorites land with regularity, but actual witnessed meteorite falls are uncommon. On average meteorites from falls are recovered only about five to ten times a year.
Let's assume for a moment that last night's fireball made it all the way down. How would we go about finding it? We'd have to gather many eyewitness reports of brightness, time and direction of travel and then triangulate a possible fall location. Meteorite hunters would then "work" the area with their eyes and metal detectors to look for fresh, black, rounded and fragmented rocks. The black coating on a fresh meteorite is called fusion crust and the result of frictional heating during its plummit through the atmosphere. Fusion crust is only a couple millimeters thick; the inside of the meteorite still holds onto the chill of outer space. Most meteorites contain iron-nickel metal which a properly tuned metal detector can detect. Another more recent technique is using Doppler weather radar to pick up the dust and debris trail from a falling meteor. Precise data like that is invaluable in helping to pinpoint the fall location.
Fragments of the Ash Creek meteorite that fell in Texas on February 15, 2009. Here are 11 stones from the collection of Karl Aston. Regmaglypts are little hollows left on a meteorite's surface after softer materials there were melted away during the fall. Credit: Randy Korotov - Washington University in St. Louis. More info HERE.
Doppler was used to help find last year's well-publicized Ash Creek fall last February near West, Texas. Needless to say, it's a lot easier to find meteorite fragments if you're searching farm fields and open prairie than a region covered by forests and lakes!
All this time I've been talking meteor fragments but there's also the small possibility the flaming object was a piece of manmade space junk. I haven't seen any postings on a listserv on the subject but a small piece coming down could easily mimic a meteor.
If you have any additional information about the object that fell, please click on the Comments link below and share your story with us. And if you have a photo, we're crazy to see it. Thanks!
(Material from the Duluth News Tribune was used in this article.)