According to astronomers at the University of Alelaide in Australia who studied radar echos from meteors for a year, found that of the 350,000 detections from small 10 - 50 micron sized meteorites, that about 1508 had velocities in excess of 100 kilometers per second. This speed is well in excess of any possible bound solar system orbit velocity, and they conclude that this population comes from outside the solar system.
They believe that these particles, which account for only 0.9 percent of the total seen between February 1990, and November 1991, are interstellar dust grains which have been known to exist for decades. The average speed of this population is 164 kilometers per second compared to 73 kilometers per second for the maximum solar system orbital speed. They also noted that the flux of these fast moving particles seems to be correlated in arrival intensity with two populations. The first of these is related to the Sun's motion around the galactic center, the second seems to be correlated with nearby A and B-type stars and young stellar clusters.
Copyright 1997 Dr. Sten Odenwald
Return to Ask the Astronomer.