61st Annual Meteoritical Society Meeting 5002.pdf

THE UPSILON PEGASID METEOR SHOWER: HISTORY AND OBSERVATIONAL CHARAC- TERISTICS. H. Povenmire, Florida Institute of Technology, 215 Osage Drive, Indian Harbour Beach FL 23937, USA.

On the morning of August 8, 1975, numerous shower is large and nearly an A.U. in diameter. faint meteors were noticed radiating from the The greatest ZHR were observed on August 7–9, Square of Pegasus [1]. This radiant was at R.A. 1978, when the rates were approximately 20 per 350 degrees and Dec. +19 degrees (2000.0). The hour. In the years following the rates declined. nearest naked eye star to this radiant is Upsilon The Upsilon Pegasids seem to appear in clumps. Pegasi, hence the name. Several will occur in a short duration of time and An extensive literature search of lists of sus- then there will be a significant lull without activ- pected radiants of W. F. Denning, A. King, and ity. The average magnitude is approximately the American Meteor Society showed numerous +3.50. The Upsilon Pegasids are best described probable candidates. The earliest was on August as faint, yellow-white and lacking significant 11, 1869 [2]. trains. Only about 6% are brighter than magni- The parabolic orbital elements were computed tude +1.0 and only the brighter ones of these first by F. Fallon and then by Z. Ceplecha using leave persistent trains lasting more than 1.0 sec- the FIRBAL Program with similar results. ond. About 7% are orange and 14% are blue in On August 19, 1982 at 2:09:57 U.T., a color [4]. magnitude –14.76 Upsilon Pegasid fireball oc- The ZHR of this shower also varies each year. curred over the White Carpathian Mountains in It is frequently just above the detection level. The Austria and Czechoslovakia. This fireball was highest recorded ZHRs occurred in 1978. photographed by six cameras of the European From careful reduction of EN 190882A, Ce- Network. This fireball has been designated EN plecha determined that these meteors are of Type 190882A. It was also observed visually and de- C. These are similar to the Draconids with a scribed as yellow-green with a 0.5 degree wide, specific gravity of approximately 0.27 g/cm3. 2.0 second persistent train [3]. They are fragile, snowlike meteors and cannot A literature search found five other photo- produce sonic phenomena or meteorites. graphic double station Upsilon Pegasids which The orbital elements of the parent comet were were listed as sporadics. The institutions report- computed from the precise orbital elements of the ing these meteors were Yale, Harvard, Sta- meteors. Assuming the parent comet is in an ex- linabad, Tadjikistan, and The Dutch Meteor So- tremely eccentric elliptical orbit, then its aphe- ciety. The averaged orbital elements have been lion or radiant point on the celestial shpere is in determined from the double station photographic Cygnus at R.A. 312 degrees, Dec +34 47’ de- meteors. grees (2000.0). Using the orbital elements, the radiant drift This radiant is being kept under yearly sur- was computed by J. Drummond and G. Kronk veilance by three multiple station photographic with similar results [4]. This slow moving radi- meteor networks. ant moves from the SSW to the NNE at about 20 The Upsilon Pegasids have been intensively arc minutes per day at an angle of approximately observed for 23 consecutive years and every year 80 degrees. since 1975 some meteors have been recorded The Upsilon Pegasids are likely an old from it. shower. The shower is intact as it is in high in- References: [1] Povenmire H. (1982) Fire- clination and free of planetary pertubations. balls, Meteors and Meteorites, JSB Enterprises, These meteors contact the Earth while approach- Indian Harbour Beach, Florida. [2] Denning ing the Sun. The meteors that occur at maximum W. F. (1899) General Catalog of Meteoric Radi- arrive at perihelion on approximately September ant Points, pp. 224–292, Memoirs of the British 16.0 at a perhilion distance of .20 A.U., just a Astronomical Association. [3] Ceplecha Z. little greater than half that of Mercury. The radi- (1982) SEAN Bulletin-Smithsonian Institution, ant has an estimated diameter of about 3 degrees. September 30, pp. 13–14, Washington, DC. [4] The broad maximum seems to be on August 8. Povenmire H. (1996) IAPPP Comm. No. 65, 28– The duration seems to extend from approxi- 31, Florida Institute of Technology, Melbourne. mately July 23 to August 29 indicating that this