On the density of meteoroids

Abstract

The density of 359 photographic meteors, reduced by Hawkins and Southworth, has been computed with a procedure that uses the height of maximum light and does not require the use of the deceleration. The reliability of the method is discussed. It is shown that neither fragmentation nor other known causes can have a large effect on the results. The meteoroids turn out to have a mean density much smaller than 1 g cm−3. The average density of the sporadic meteors, according to the present analysis, is about 0.2 g cm−3. The densities of the members of the principal showers have also approximately the same value. These low densities conform to expectation on the basis of Whipple’s icy-comet model and agree with the porous and crumbling structure shown by all photographic meteors but the brightest fireballs. The meteor density obtained in the present analysis is essentially the same as that previously obtained by the author for the photographic meteors precisely reduced by Jacchia. It is confirmed that short-period meteors have on the average a greater density than meteors with elongated orbits. No conclusive evidence was found in the Hawkins-Southworth material for any meteor of definite asteroidal origin.