Temperatures of lunar impact flashes: mass and size distribution of small impactors hitting the Moon

C Avdellidou,J Vaubaillon

doi:10.1093/mnras/stz355

Abstract

Lunar impact flashes have been monitored over the last 20 years for determining the mass frequency distribution of near-Earth objects in the cm-dm size range. In this work, using telescopic observations in R and I band from the NELIOTA database, impact flash temperatures are derived. They are found to range between approximately 1,300 and 5,800 K. In addition, it is also found that temperature values appear to have a distribution significantly broader than a Gaussian function, therefore making it difficult to estimate the impact flash luminous energy by assigning an average temperature. By measuring the flash temperatures and assuming a black body emission, here we derive the energy of the impacts. We also study the potential link of each event to individual meteoroid streams, which allows us to assign an impact velocity and therefore constrain the projectile mass. Impactor masses are found to range between a few to hundreds of grams, while their sizes are just of few centimetres following a size frequency distribution similar to other studies.

Highlights

Almost two decades ago the lunar surface started to be monitored with small-aperture telescopes (e.g. 40 cm) for the detection of the light of flashes produced by the impacts of near-Earth objects (NEOs) (Ortiz et al 1999, 2000, 2002, 2006, 2015; Bouley et al 2012; Suggs et al 2008, 2014; Madiedo et al 2014, 2015; Ait Moulay Larbi et al 2015)
The idea to monitor the lunar surface using photomultipliers was already introduced since the beginning of 90’s by Melosh et al (1993), when it was modelled that impact flash events should be detectable on the lunar surface using modest telescopes equipped with photometers, but the impactor size had to be in the order of 1 m and those events are very rare
In this work is presented the methodology to measure the temperatures of the lunar impact flashes from NELIOTA 2-colour measurements by using the total response of the detectors and the peak wavelength as in previous studies

Summary

Introduction

Almost two decades ago the lunar surface started to be monitored with small-aperture telescopes (e.g. 40 cm) for the detection of the light of flashes produced by the impacts of near-Earth objects (NEOs) (Ortiz et al 1999, 2000, 2002, 2006, 2015; Bouley et al 2012; Suggs et al 2008, 2014; Madiedo et al 2014, 2015; Ait Moulay Larbi et al 2015). The idea to monitor the lunar surface using photomultipliers was already introduced since the beginning of 90’s by Melosh et al (1993), when it was modelled that impact flash events should be detectable on the lunar surface using modest telescopes equipped with photometers, but the impactor size had to be in the order of 1 m and those events are very rare. It was not until 2000 when the first impact flash was recorded (Ortiz et al 2000), using ccd cameras instead of photometers. Lunar flash monitoring offers the advantage that Moon’s surface provides an extended area for detections, whereas the Earth-based sky monitoring systems that search for bolides do not have such a large detection area.

Results

Discussion

Conclusion