Observations of the new meteor shower from comet 46P/Wirtanen

Context. A new meteor shower λ-Sculptorids produced by the comet 46P/Wirtanen was forecast for December 12, 2023. The predicted activity was highly uncertain, but generally considered to be low. Observations in Australia, New Zealand, and Oceania were solicited to help constrain the size distribution of meteoroids in the shower. Aims. This work aims to characterize the new meteor shower, by comparing the observed and predicted radiants and orbits, and to provide a calibration for future predictions. Methods. Global Meteor Network video cameras were used to observe the meteor shower. Multi-station observations were used to compute trajectories and orbits, while single-station observations were used to measure the flux profile. Results. A total of 23 λ-Sculptorid orbits have been measured. The shower peaked at a zenithal hourly rate (ZHR) of 0.65−0.20+0.24 meteors per hour at λ⊙ = 259.988° ±0.042°. Due to the low in-atmosphere speed of 15 km s−1, the mean mass of observed meteoroids was 0.5 g (∼10 mm diameter), an order of magnitude higher than predicted. The dynamical simulations of the meteoroid stream can only produce such large meteoroids arriving at Earth in 2023 with correct radiants when a very low meteoroid density of ∼100 kg m−3 is assumed. However, this assumption cannot reproduce the activity profile. It may be reproduced by considering higher density meteoroids in a larger ecliptic plane-crossing time window (ΔT = 20 days) and trails ejected prior to 1908, but then the observed radiant structure is not reproduced.