Lunar Leonids Predictions by Robert McNaught
Updated: 2000 Nov. 1Lunar Leonids Predictions by Robert McNaught [From an IMO-News email dated 2000 Oct. 27] Rob McNaught[SMTP:rmn@aaocbn.aao.gov.au] [IMO-News] Leonids on the Moon I was too late to get the following note to Tony Phillips for his excellent Science@NASA article at http://www.spacescience.com/headlines/y2000/ast26oct_1.htm Lunar Leonids: encounters of the Moon with Leonid dust trails. Robert H. McNaught, Siding Spring Observatory Last update 2000/10/27 The following table lists all encounters of the Moon with dust trails within 0.0010 AU during the current epoch. Only the trails discussed in ref [1] are considered. The calculations are based on the formulae given in [2]. In every year, a test date was used to derive the approximate magnitude of the Moon's distance towards (-ve) or away from (+ve) the Sun in relation to the Earth (rE-rM). This was then directly compared with values for dust trail encounters with the Earth given in [1] and close approaches were further investigated. An iterative process is necessary, as the motion of the Moon during the tens of minutes between Earth and Moon encounters with dust trails must be taken into account. The resulting time correction (dt) from the Earth encounter time in [1] is given along with the distance of the nominal trail center from the Moon (rM-rD). Finally, an approximate ZHR indicates the relative activity of these encounters. This is derived using the same form of analysis as in [1] and can be compared with the predicted values for the Earth [3]. It seems clear that 1999 was the year for lunar Leonids but the years 2000 and 2001 could have some substantial activity. It is notable that several of these encounters are unlikely to produce meteor showers on the Earth, but as the Earth-Moon system is passing through the midst of the comet 55P/Temple-Tuttle dust trail complex in 2000 and 2001, several encounters occur in each year for both the Earth and Moon. The circumstance of resonant Leonids striking the Moon in 1998 may require further examination. The 1333 trail is at a distance rE-rM = +0.0026 AU, so it may not have been the culprit of the enchanced sodium tail. However, another resonant trail may have passed closer to the Moon and I've asked David Asher about this. David has noted that these old resonant trails are broader than the young trails, so perhaps this greater miss distance is less relevant. It is also the case that the greater mass of the particles in these resonant trails could result in substantially more mass impacting the Moon in 1998 despite this greater miss distance than the probable lunar Leonid storm in 1999. re-rm rm-rd dt Time of AU trails AU min lunar max. "ZHR" 1997 Nov. 18.0 -0.0018 none 1998 Nov. 17.013 +0.0025 none (20-rev +0.0026 -31) 1999 Nov. 18.089 -0.0009 3-rev +0.0002 +163 Nov. 18 04:51 UT 50,000 2000 Nov. 17.327 -0.0006 2-rev -0.0006 -175 Nov. 17 04:58 UT 1,000 18.156 -0.0002 8-rev +0.0010 -172 18 03:52 UT 10 18.327 -0.0001 4-rev +0.0009 -170 18 05:01 UT 50 2001 Nov. 17.595 +0.0022 1-rev 0.0000 +106 Nov. 17 16:03 UT 500 18.505 +0.0020 6-rev -0.0006 +128 18 14:16 UT 1,000 18.595 +0.0020 5-rev -0.0003 +130 18 16:28 UT 5,000 2002 Nov. 19.44 -0.0027 none 2003 Nov. 18.1 +0.0006 none 2004 Nov. 19.0 +0.0002 none 2005 Nov. 19.0 -0.0021 none 2006 Nov. 19.2 +0.0025 none References [1] R.H. McNaught, D.J. Asher, "Leonid dust trails and meteor storms", WGN 27, 1999, pp. 85-102. [2] R.H. McNaught, D.J. Asher, "Variation of Leonid maximum times with location of observer", Meteorit. Planet. Sci. 34, 1999, pp. 975-978 [3] D.J. Asher, R.H. McNaught, "Expectations for the 2000 Leonids", WGN 28, 2000, pp. 134-139 -------------------------- eGroups Sponsor --------------- eLerts It's Easy. It's Fun. Best of All, it's Free! http://click.egroups.com/1/9699/13/_/70339/_/972625258/ ----------------------------------------------------------