Astronomers at NASA's Marshall Space Flight Center (MSFC) have recorded the brightest meteor seen by their network, in almost three years of operation. On the night of 20 May 2011, a 2-meter-wide fragment of an unknown comet penetrated the atmosphere, approximately 110 km above the city of Macon, Georgia, USA. It was traveling northwest, at a speed of about 38 km/s (approximately 140,000 km/h). At this velocity, the space intruder packed an energy of at least 500 tons of TNT. It eventually disintegrated, in the last few seconds of its dazzling atmospheric plunge.
This was witnessed by many persons in the states of Georgia and Alabama; the American Meteor Society published some of the reports online:
http://www.amsmeteors.org/fireball2/public.php?start_date=2011-05-01&end_date=2011-05-31&state=&event_id=511&submit=Find+Reports
The meteor was monitored by two NASA all sky cameras, one located in Chickamauga, Georgia, and the other at the Tellus Science Museum in the town of Cartersville, Georgia. Analysis of the video data from these cameras enabled the Meteoroid Environment Office to determine the trajectory, speed, mass and orbit of the meteor.
Meteors are among the smallest objects of the Solar System. They are dust- to pebble-sized particles, in orbits around the Sun. They occur at altitudes of about 100 km. When a meteor streaks through our atmosphere, it glows for a few seconds, and breaks up, due to the high force of drag, resulting from its rapid descent. A meteorite is larger and more massive than a meteor, and can survive atmospheric entry, eventually impacting the ground. Some meteorites are quite large, however, the risk of a person being hit by a meteorite is very small.
References
NASA
http://www.nasa.gov/topics/solarsystem/features/watchtheskies/macon.html
Wikipedia