We've heard it called many things, a sign of the end of times or as "Armageddon" at the cinema. However asteroids have become a much more publicly aware reality than a scientific phenomenon. Just after sunrise today, an estimated 10 ton meteor flew through the earth's atmosphere at hypersonic speed around 33,000 mph! To put that into perspective, the Blue Angles reach speeds of 700 mph and the record fastest pitch was set by Aroldis Chapman at 105 mph, so 33,000 mph is hard to wrap your mind around! It shattered about 18 to 32 miles above ground raining its debris over a large area over the Ural Mountains of Russia. Many people who saw the event in the Chelyabinsk region said it looked like an incredibly bright fireball. There are reports of over 750 people injured, mostly from shattered windows & glass from the sonic boom. The "explosion" heard was from the shock wave of the meteoroid.
"I would think that this is likely an exploding fireball (or bolide) event caused by the atmospheric impact of a small asteroid," Don Yeomans, head of NASA's Near-Earth Object Program. "If the reports of ground damage can be verified, it might suggest an object whose original size was several meters in extent before entering the atmosphere, fragmenting and exploding due to the unequal pressure on the leading side vs. the trailing side." Yeomans added, the meteor "pancaked and exploded."
So we could be talking about an object around 10 to 20 ft. before entering the earth's atmosphere, fragmenting, and then exploding. The raining chunks that exploded (the meteorites) found downrange will give scientists a better idea of its size and what it was made of (rock, metal, or both). Scientist Phillip Plait explained that looking at a number of the incredible videos of the event, the train (term for meteor trail) was shown for some time before you hear the explosion which would explain the sound coming from the shock wave from the meteoroid going through our atmosphere high above the ground. That "boom" happens when a large mass is moving at multiple times the speed of sound through the air. The train also seems to split, so that could be where the main mass split leading to debris falling in multiple locations.
All this seems to be a HUGE coincidence that it comes on the same day that asteroid 2012 DA14 will come 17,200 miles close to the Earth. The two events have been deemed unrelated by NASA, as they are on two completely different paths. DA14 poses no threat to us, but is a great opportunity for scientists to observe & get a better understanding of orbit characteristics. These events tend to be random and some are difficult to track, especially smaller NEO's (near-Earth objects) like the one that moved over Russia today. There have been many agencies put into place to research & track NEO's which are comets & asteroids that are pushed by gravitational attraction of nearby planets into orbits that move them into Earth's neighborhood. I don't know about you, but I hope we aren't that attractive because that is not the type of neighbor I want moving in!
Picture courtesy of Dave Herald on 2/12/13 when 2012 DA14 was still 770,000 miles from Earth.
So why is it so hard to predict when pieces of these asteroids are going to cause major problems like what we saw today? NEO discovery teams use CCD cameras (charged couple devices) similar to those in camcorders that record images digitally in many electronic pixels. When looking at how close a NEO is to Earth, the teams need to look at the objects location through multiple images, the direction its going, & its brightness to get a glimpse at its path & general orbit characteristics. With this morning's meteor possibly being 10 to 20 feet, that is very small compared to DA14 which looks to be about 164 feet and grazing the earth within 17, 200 miles. DA14 is the largest object of its kind to be seen coming this close to Earth.
You can watch all the action at www.nasa.gov at around 1:25pm Central when it is closest to the Earth, visible only by telescope to Europe, Australia, & Asia at that point. But we will get some action too around 8pm Central when larger telescopes catch a glimpse of it passing our neck of the woods. Nasa will be doing a live stream of the entire event for your viewing pleasure!
In the end, it's is a scary thing to think about. For most of us who spend a lot of our time looking down, I know I will spend more time looking up from now on! Our solar system is full of mysteries just waiting to be unlocked, and I am sure scientists will continue to look for those keys to help us understand what the heavens have in store for us. Or we could just take R.E.M.'s approach and sing, "It's the end of the world as we know it, and I feel fine".