Everyone knows about meteors, also known more commonly as shooting stars. Less common are something called fireballs, which have an altogether different effect. Instead of a quick sliver of light that happens so quickly it’s sometimes hard to tell if it’s been seen at all, a fireball burns brightly for lengthy time, then blows up, leaving behind a sound as loud as a sonic boom. That according to Dr. Tony Phillips of NASA, on NASA’s Science News page. He writes also that those that are interested in finding out more about them can visit the NASA web site dedicated exclusively to them.
The reason they behave differently, Phillips explains, is because they’re moving a lot slower than so-called normal meteors, plus they strike at a different angle. Meteors that slice across the sky and disappear in an instant are traveling so fast that they almost bounce off the atmosphere. And because they are moving so fast, they burn fast, disappearing in an instant. In contrast, fireballs tend to come at the Earth in a more dead on position, blunting both their angle and speed. Thus, those that are seen appear to grow brighter as it comes closer. But then, because the closer they come, the faster they get due to Earth’s gravity. This makes them grow hotter and hotter until they simply explode in a giant burst of light that can be brighter than that from the moon. That’s usually followed by a loud boom, as the sound catches up to light that has already made its way to the surface.
All this comes about as news of fireballs over rural Georgia and Texas have made the newspapers. Some have taken to calling them the “Fireballs of February” Phillips writes, noting that such people are right. Fireballs are most prevalent during the month of February, and this one is no exception. One such fireball, he says appeared directly over the Dallas-Fort Worth area on the 1st of the month causing some fear and consternation among the local citizenry. Witnesses say it took a full eight seconds from the time it first appeared, till it exploded, emitting light so bright it could be seen as far away as New Mexico.
NASA says on its site that thus far, more than half a dozen fireballs have been seen this year, and they expect several more before the month is over. They also mention that there is very little to fear from the fireballs, as it would be nearly impossible for one to survive long enough to reach the ground. Thus, they suggest, if people see them, just stop and enjoy the view.