Modeling the 2022 τ-Herculid Outburst

Abstract

The τ-Herculids (IAU shower number 61 TAH) is a minor meteor shower associated with comet 73P/Schwassmann–Wachmann 3, a Jupiter-family comet that disintegrated into several fragments in 1995. As a consequence of the nucleus breakup, possible increased meteor rates were predicted for 2022. On May 30–31, observation networks around the world reported two distinct peaks of TAH activity, around solar longitudes 69.°02 and 69.°42. This work examines the encounter conditions of the Earth with meteoroids ejected from 73P during the splitting event and on previous perihelion passages. Numerical simulations suggest that the main peak observed in 2022 was caused by meteoroids ejected from the splitting nucleus with four times the typical cometary gas expansion speed. High-resolution measurements performed with the Canadian Automated Meteor Observatory indicate that these meteoroids are fragile, with estimated bulk densities of 250 kg m−3. In contrast with the main peak, the first TAH activity peak in 2022 is best modeled with trails ejected prior to 1960. We find that ordinary cometary activity could have produced other TAH apparitions observed in the past, including in 1930 and 2017. The extension of our model to future years predicts significant returns of the shower in 2033 and 2049.

Not So Fast: A New Catalog of Meteor Persistent Trains

“…The remaining three were likely due to older trails, however one of these older meteoroids still produced a PT. Though Schwassmann-Wachmann 3 is a JFC, the estimated bulk density of its meteoroids is very low-around 250 kg m 3 (Egal et al, 2023), which is even lower than the Leonids'. Consequently, this material is quite fragile and prone to fragmentation.…”

“…Two distinct activity peaks were noted during the 2022 outburst. According to simulations done by Egal et al (2023), the first, smaller peak arose from older, pre-breakup trails, while the main activity peak was traced to the 1995 breakup. All but three of the τ-Herculid meteors we observed had solar longitudes greater than 69.39, consistent with material from the splitting event.…”

“…Out of 76 meteors, 37 left behind noticeable PTs (48.7%) and all 76 penetrated below the altitude threshold. Though the τ-Herculids are usually considered an inactive shower, their parent comet 73P/Schwassmann-Wachmann 3 underwent a large-scale fragmentation event in 1995 and divided into at least 4 main fragments; this breakup and subsequent crumbling was predicted to cause considerably increased meteor rates during its 2022 shower (Egal et al, 2023). As a testament to its low activity, the GMN observed only one multi-station event for each 2021 and 2023, but saw more than 1,240 events in 2022.…”

“…Whether the freshness of this material played a role in their elevated PT formation rate remains to be seen. The τ-Herculids are predicted to return with stronger showers in 2033 and 2049, again primarily due to material from the 1995 fragmentation (Egal et al, 2023), providing a good opportunity for additional study.…”