TPIE DETERMINATION OF METEOR-ORBITS IN THE 

 SOLAR SYSTEM 



By G. von NIESSL 



(Translation by the late Prof. Cleveland Abbe, with permission of the 



author and publisher, from the Encyclopiidic der Mathematischcn 



Wissenscliaften, Band 6, Part 2, Heft 3. Dated Vienna, 1907.) 



GENERAL THEORY 



The orbits of those bodies which, by their entrance into the atmos- 

 phere, become incandescent meteors, have a planetary character in 

 the solar system. They are conic-sections with the sun as one focus. 

 That portion of the path revealed to us by observations is so short, 

 that it must be assumed to be a straight line even in the most accurate 

 determinations. Irregular movements that are conditioned by the 

 §hape of the body occasionally occur, but are here left out of 

 consideration. 



For all orbits that thus becoiiie visible, the smallest distance from 

 the earth's center, or in geocentric phraseology, the perigee, is very 

 small in comparison with the distance from the sun or the corre- 

 sponding radius vector of the orbit of the earth, and can be neglected 

 in comparison therewith. Hence, for the duration of fall the helio- 

 centric radius vector of the meteor's path will be assumed as identical 

 with that of the eartiys orbit. Furthermore, since for the same 

 reason, the collisions with the earth can be considered as identical 

 with the passage of the meteor through one of the nodes of its path, 

 therefore from the solar ephemeris for the date of collision we find 

 directly the longitude and the radius vector of that node of its path. 



The apparent location of the visible path of the meteor in the sky, 

 depends parallactically on the location of the station of observation. 

 It will, therefore, for the near-by meteors show greater apparent dis- 

 location than for those more distant. Any point of the rectilinear 

 path or its prolongation backwards, that is so far removed from all 

 observing stations that their respective mutual distances no longer 

 come into consideration, will be seen at the same point in the sky from 

 all stations. This perspective point of divergence of the apparent 

 paths instead of the true paths as seen from different places on the 

 earth is the point of apparent radiation or convergence. This deter- 



Smithsonian Miscellaneous Collections, Vol. 66 No. 16. 



