Statistical Analysis of Lunar Impact Flashes

Over 850 lunar impact flashes (LIFs) have been reported in the literature and online databases by a wide range of observational campaigns and amateur astronomers [1, 2, 3, 4]. The introduction of PyNAPLE [5], a software package developed to identify craters formed by LIFs, enabled a revised calculation of the luminous efficiency [6]. This parameter is fundamental to LIF studies, as it quantifies the proportion of an impactor’s kinetic energy that is converted into observable light. Consequently, any revision to the luminous efficiency has significant implications for subsequent derived parameters.

 

Here, we revisit all previously reported LIFs using the updated luminous efficiency and expand the dataset to include all additional events recorded to date.

 

Using meteoroid stream determination software [7], we identify the likely parent stream(s) of the impactors, from which we derive properties including impact velocity, impact angle, and density. For flashes observed in multiple wavelength bands, we determine the blackbody temperature of the emission, while for events persisting over multiple frames, we examine the temperature evolution throughout the flash duration. We additionally estimate the diameters of the resulting craters, providing constraints to support future crater searches with tools such as PyNAPLE.

 

The revised luminous efficiency is larger than values previously adopted, meaning that a given impact generates more observable light and therefore corresponds to a smaller impactor than earlier estimates implied. This may account for the difficulty in detecting LIF-associated craters with PyNAPLE, as the craters produced by the faintest observable flashes are comparable to, or smaller than, the pixel scale of the Lunar Reconnaissance Orbiter Narrow Angle Camera (~0.5 m/px). We present the outcomes of these updated calculations along with revised statistical properties of the dataset, including the size–frequency distribution of the observed impacts.

 

References

1. Suggs R. M., Moser D. E., Cooke W. J., Suggs R. J., 2014, Icarus, 238, 23

2. Avdellidou C., et al., 2021, Planet. Space Sci., 200, 105201

3. Sheward D., Delbo M., Avdellidou C., Cook A., Lognonné P., 2025, A&A,699, L3

4. Liakos A., Bonanos A. Z., Xilouris E. M., Koschny D., Bellas-Velidis I., Boumis P., Maroussis A., Moissl R., 2024, A&A, 687, A14

5. Sheward D., Avdellidou C., Cook A., Sefton-Nash E., Delbo M., Cantarella, B., Zanatta L., 2022, MNRAS, 514, 4320

6. Sheward D., Delbo M., Avdellidou C., Cook A., Lognonné P., 2025, A&A, 699, L3

7. Avdellidou C., Vaubaillon J., 2019, MNRAS, 484, 5212