Very precise orbits of 1998 Leonid meteors

Abstract

Abstract-Seventy-five orbits of Leonid meteors obtained during the 1998 outburst are presented. Thirtyeight are precise enough to recognize significant dispersion in orbital elements. Results from the nights of 1998 November 16/17 and 17/18 differ, in agreement with the dominant presence of different dust components. The shower rate profile of 1998 November 16/17 was dominated by a broad component, rich in bright meteors. The radiant distribution is compact. The semimajor axis is conjined to values close to that of the parent comet, whereas the distribution of inclination has a central condensation in a narrow range. On the other hand, 1998 November 17/18 was dominated by dust responsible for a more narrow secondary peak in the flux curve. The declination of the radiant and the inclination of the orbit are more widely dispersed. The argument of perihelion, inclination, and the perihelion distance are displaced. These data substantiate the hypothesis that trapping in orbital resonances is important for the dynamical evolution of the broad component.

Image‐intensified video results from the 1998 Leonid shower: I. Atmospheric trajectories and physical structure

“…The vast majority of sporadic and shower meteors have beginning heights (as measured by two-station image intensified video techniques) in the range from 90 to 120 km (Hawkes and Jones, 1980;Hapgood et al, 1982;Hawkes et al, 1984;Sarma and Jones, 1985;Ueda and Fujiwara, 1995). However, previous two-station studies of Leonid meteors have found beginning heights for a few bright fireballs as high as 160 km (Fujiwara et al, 1998) to 200 km (Betlem et al, 1999). One possible interpretation of these observations is that the meteoroids are much more volatile than conventional theory suggests.…”

Precise data on Leonid fireballs from all-sky photographic records

“…This was observed previously by Betlem et al (1999) and Trigo-Rodriguez et al (2002). Betlem et al (1999) concluded that this can only occur after a close encounter with Earth, and that in order to detect a significant number of such meteoroids, the Earth would have had to cross appropriate dust trails numerous times in the past. Since the Leonids are very fast and their atmospheric trajectories are short, one of the less accurate observed parameter is velocity.…”

“…• , δ = 22.04 (Betlem et al 1999). Mean radiants in individual years and for individual dust trails differ from each other but merge in the range of one standard deviation.…”

Do comets have chondrules and CAIs? Evidence from the Leonid meteors

“…First, the Leonids are faster, at 71.6 ± 0.3 km/sec (e.g., Betlem et al 1999) and, hence, brighter than any other regular meteor shower. Second, although the Leonids normally consist of only about 10 meteors per hour on midNovember nights, there has been a series of Leonid "storms" since 1998, with more than 1000 meteors per hour in several cases.…”