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LEONID DAILY NEWS: December 25, 2000

Farley cartoon (SF Chronicle) San Francisco Chronicle - 12/27/00

Ursid ZHR Figure Left: Compilation of Zenith Hourly Rate estimates for the 2000 Ursid shower. The figure contains the IMO averages in red (see below) and measurements from 24 observers in Japan (black circle -compiled by Masaaki Takanashi of the Nippon Meteor Society), several observers of the Dutch Meteor Society (black square - compiled by Marco Langbroek), and visual counts by Peter Jenniskens in California (open square). Line is a best fit Lorentz profile.


The 2000 return of this shower was eagerly awaited because an enhanced activity was expected. Indeed, the rates were significantly higher than the average. The last reported Ursid activity enhancement occurred on Dec. 22, 1996 at solar long. 270.7 with ZHR of the order of 30 (But see graph right, few US observations included -PJ).

In 2000 the conditions were good as the Moon was almost new. The long northern nights allow a good overlap. Unfortunately, this first summary indicates that the most interesting period is not well covered. Most European observers had to finish around 6h UT (morning twilight). The number of North American data is scarce so far. As a consequence, we cannot yet achieve a good profile. Below find the preliminary data. The high ZHR at the end agrees with Japanese data published here before, although the errors are still quite large.

We are very grateful to the following 15 observers who sent in their reports in time for this first activity overview:

ARLRA Rainer Arlt (Germany), BADPI Pierre Bader (Germany), BUCAN Andreas Buchmann (Switzerland), CANED Ed Cannon (USA), ENZFR Frank Enzlein (Germany), HOSDA Dave Hostetter (USA), LANMA Marco Langbroek (Netherlands), LUNRO Robert Lunsford (USA), LUTHA Hartwig Luthen (Germany), MOLSI Sirko Molau (Germany), OSAKA Kazuhiro Osada (Japan), PUNMI Milesh Puntambekar (India), RENJU Jurgen Rendtel (Germany), STOEN Enrico Stomeo (Italy), ZHUJI Jin Zhu (China)

Date   Time (UT)  Sollong nObs nIND  nURS       ZHR  +/-
Dec 22    0240    270.553    5     4     16         5.1 +- 1.2
       22    0330    270.586  12     9     46         8.2     1.2
       22    0410    270.620  16     9     76        12.7    1.5
       22    0510    270.658  16   10   104        19.6     1.9
       22    0535    270.676    8     6     58        26.1     3.4
       22    0935    270.847    2     2     29        53      10
Solar longitudes refer to equinox J2000.0. nObs is the number of individual observing periods, nIND is the number of individual observers providing them, nURS is the number of Ursids seen. The population index used was r=2.5. The expectation value of the ZHR,
ZHR = (1 + sum nGEM) / sum(Teff/C),
was used for the averages here, where Teff is the effective observing time and C is the total correction composed of limiting magnitude, clouds, and zenith correction [sin (h_R)]. Times are rounded to the nearest 10 minutes. - Juergen Rendtel, International Meteor Organization (December 25, 2000).

Previous news items:
Dec. 25 - Ursid shower circular IMO
Dec. 24 - Ursid shows early release of sodium
Dec. 23 - Ursid outburst confirmed
Dec. 18 - Dec 22 Ursid outburst
Nov. 20 - A bacterial fingerprint?
Nov. 15 - HCN disappears mysteriously
Nov. 14 - Meteor shower from space
Nov. 13 - Organic fingerprint
Nov. 12 - Train airglow chemistry
Nov. 11 - Hard bits and persisting glows
Nov. 10 - Meteoroid debris detected
Nov. 09 - New meteor picture
Nov. 08 - Spin city
Nov. 07 - Meteors affect atmospheric chemistry
Nov. 06 - Listen to this!
Nov. 04 - Fear of heights?
Nov. 03 - The pale (infra-red) dot
Nov. 02 - Twin showers
Nov. 01 - Leonids approaching Earth
Oct. 31 - Prospects for Moon Impact Studies
Oct. 30 - Comet dust crumbled less fine
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Results of this work were published in Icarus.

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