Giant Meteor Seen (and Heard) Above California
April 27, 2012
A giant fireball, a meteor, lit up the sky above the Sierra Nevada Mountains near Sutter’s Mill, California, early on April 22. Seen from as far away as Sacramento, the state capital, and Reno, Nevada, the fireball was caused by a meteoroid, a piece of primordial matter from space.
A meteoroid becomes visible when it enters Earth’s atmosphere from space at very high speed. As the meteoroid collides with the atmosphere, friction causes it to heat up so that it glows, creating a shining trail of hot gases. Most meteoroids are smaller than a pebble and break apart in a second or less.
A meteor appears in the sky when an object called a meteoroid enters the atmosphere from space. (World Book illustration by Greg Maxson)
Scientists believe that the meteoroid that hit the atmosphere with a loud explosion over California probably weighed about 154,300 pounds (69,990 kilograms) and was as large as a minivan. They calculated that it hit the atmosphere with about one-third the explosive force of an atomic bomb. The loud boom heard as the meteoroid streaked across the sky was caused by the speed with which the rock entered the atmosphere. Scientists estimate the meteoroid was traveling up to 44,000 miles (80,000 kilometers) per hour–many times faster than the speed of sound–when it hit the atmosphere. This caused the gigantic sonic boom heard across two states.
Thousands of meteorites rained down over hundreds of square miles as the fireball broke apart in the sky. Meteorites are meteoroid fragments that reach the Earth’s surface intact. By midweek, collectors had found several meteorites weighing about 1/3 ounce (10 grams) each. After examining the fragments, scientists determined that the large meteoroid was a rare, carbon-rich type known as a carbonaceous chondrite. This type of meteorite is made up of the same material from which the planets formed and dates to the very beginnings of the solar system more than 4 billion years ago. Scientists hope to find even more fragments of this rare meteor event.
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