Impact Flashes Research Articles

NELIOTA: New results and updated statistics after 6.5 years of lunar impact flashes monitoring

We present results of the Near-Earth objects Lunar Impacts and Optical TrAnsients (NELIOTA) campaign for lunar impact flashes observed with the 1.2 m Kryoneri telescope. From August 2019 to August 2023, we report 113 validated and 70 suspected flashes. For the validated flashes, we calculate the physical parameters (masses, radii) of the corresponding projectiles, the temperatures developed during the impacts, and the expected crater sizes. For the multiframe flashes, we present light curves and thermal evolution plots. Using the whole sample of NELIOTA that encompasses 192 validated flashes in total from 2017, the statistics of the physical parameters of the meteoroids, the peak temperatures of the impacts, and the expected crater sizes has been updated. Using this large sample, empirical relations correlating the luminous energies per photometric band were derived and used to roughly estimate the parameters of 92 suspected flashes of the NELIOTA archive. For a typical value of the luminous efficiency, we found that the majority (>75%) of the impacting meteoroids have masses between 1 and 200 g, radii between 0.5 and 3 cm and produced craters up to 3.5 m. 85% of the peak temperatures of the impacts range between 2000 and 4500 K. Statistics regarding the magnitude decline and the cooling rates of the multiframe flashes are also presented. The recalculation of the appearance frequency of meteoroids (lying within the aforementioned ranges of physical parameters) on the Moon yields that the total lunar surface is bombarded with 7.4 sporadic meteoroids per hour and up to 12.6 meteoroids per hour when the Earth-Moon system passes through a strong meteoroid stream. By extrapolating these rates on Earth, the respective rates for various distances from its surface are calculated and used to estimate the probability of an impact of a meteoroid with a hypothetical infrastructure on the Moon, or with a satellite orbiting Earth for various impact surfaces and duration times of the missions.

Cloud reflection modelling for impact flashes on Jupiter

Aims. We investigate the optical characteristics of flashes caused by the impact of metre- to decametre-sized outer Solar System objects on Jupiter, and the contributions of reflected light from surface clouds at visible wavelengths, in order to estimate more accurate bulk parameters, such as the luminous energy of the flash, the kinetic energy, the mass, and the size of the impact object. Methods. Using the results of recent reflectivity studies of the Jovian surface, we developed a cloud reflection model that calculates the contribution of the reflected light relative to that directly from the flash. We compared the apparent luminous energy of the previously reported flashes with the expected cloud reflection contributions to obtain their revised bulk parameters. Results. We find that cloud reflection contributions can make up to 200% of the flux directly from the flash, and thus can be the most significant uncertainty in the measurement of the bulk parameters. The reflection contributions strongly depend on wavelength. With our cloud reflection correction, we obtained revised bulk parameters for the previously reported flashes. Conclusions. Our cloud reflection correction enables us to better understand the properties of objects impacting Jupiter and is crucial for ongoing detailed investigations using high-sensitivity and multi-wavelength observation systems, such as PONCOTS. It will also be useful for understanding other optical transients in Jupiter’s upper atmosphere, such as the recently discovered sprite-like events.

Modelling the optical energy profile of the 2021 October Jupiter impact flash

ABSTRACT We have conducted numerical simulations to reproduce the observed optical energy profile of the 2021 October 15 (ut) impact flash on Jupiter, which was the largest and the most well-observed flash event detected by ground-based movie observations. The observed long-duration (∼5.5 s) optical emission can be reproduced by an impact of an object with an exceptionally small angle of entry relative to the horizontal. The apparent lack of the impact debris feature despite the large impact object was possibly due to the shallower angle of entry (≤12°), which resulted in the lower ablation per unit volume at altitudes higher than $50 \, {\rm km}$, and the volume densities of the ablated materials were too low to allow the debris particulates to coagulate. The absence of temporal methane absorption change in the observed flash spectrum is consistent with the best-fitting results. The model better fits the observed optical energy profile for weaker material (cometary and stony) cases than for metallic ones. Based on the simulation results, prospects for future observations of impact flashes are discussed.

Ay Çarpma Parlamalarının Gözlenmesi

Ay Çarpma Parlamaları, yüksek hızlarda Ay yüzeyine çarpan göktaşlarının oluşturduğu kısa süreli parlamalardır. Çarpma anında, çarpan cismin kinetik enerjisinin bir kısmının ısısal enerjiye dönüşmesiyle oluşan bu parlamalar Yer’den teleskoplarla gözlenebilmektedir. Ay çarpma parlamaların gözlemi, çarpan cismin kütlesi, çarpma sonucu oluşan krater boyutları ve çarpma olayının sıcaklığı gibi bilgilere ulaşmayı sağlamaktadır. Bu çalışmada, Ay çarpma parlamalarının gözlem yöntemi ve Türkiye’de gerçekleştirilen çalışmalar sunulmaktadır.

Gamma‐ray production in supermassive black hole binary OJ 287

AbstractOJ 287 is one of the most studied BL Lac objects with very long optical measurements whose spectrum has been well measured through radio to X‐ray band. The most outstanding characteristic of OJ 287 is its 12‐year period, which is discovered in the optical range and has also been confirmed in the X‐ray band. OJ 287 is supposed to be a binary black hole system in which a secondary black hole passes the accretion disk of the primary black hole and produces two impact flashes per period. It has also been proposed to be a GeV–TeV source. Observations of OJ 287 in the GeV–TeV energy range reveal the variable γ‐ray connected with the flare activity of this object. The spectral energy distributions of blazars consist of two broad peaks. The first, lower frequency peak is due to the synchrotron emissions of relativistic electrons in the jet. Leptonic and hadronic emission mechanisms are considered to describe the second, higher frequency spectrum part. The inverse Compton emissions of the same electrons (synchrotron self‐Compton model) or combined with an external Compton mechanism are considered in the leptonic scenario. The last one supposes the existence of the external to jet photon cloud. The high‐energy spectrum part is also supposed to be generated due to the acceleration of the cosmic ray hadrons in shock produced by outflow, which expands and then collides with the wind of the primary black hole. The detection of GeV–TeV energy fluxes can help find the parameters of the configuration of the two‐black hole system.

Meteoroids detection with the LUMIO lunar CubeSat

The Lunar Meteoroid Impacts Observer (LUMIO) is a CubeSat mission to observe, quantify, and characterize the meteoroid impacts on the lunar farside by detecting their flashes. This complements the knowledge gathered by Earth-based observations of the lunar nearside, thus synthesizing global information on the lunar meteoroid environment and contributing to the lunar situational awareness. The goal of LUMIO is to advance our current knowledge of meteoroid models in the solar system. In this work, we present the methodology devised to predict the scientific contribution of LUMIO. Our approach relies on combined modeling and simulation of payload, orbit, and environment. The analyses carried out have been used to drive the design of the LUMIO mission and its payload, the LUMIO-Cam. A payload radiometric model is derived and exploited to assess the quality of the scientific measurements. A dedicated study about straylight rejection is carried out to assess how straylight noise affects LUMIO-Cam measurements. Our results indicate that a 150mm baffle grants good performance when the Sun angle is between 20° and 90°. Furthermore, the present-day LUMIO mission has the potential to detect more than 6000 impact flashes during the activity peak of the Geminids in 2024 in the range of the equivalent impact kinetic energy at Earth of [10−6,10−1]kton TNT Equivalent. Compared to previous programmes, LUMIO could refine information and fill the knowledge gap about the meteoroid population in the ranges of the equivalent impact kinetic energy at Earth of [10−6,10−4]kton TNT Equivalent and [10−4,10−1]kton TNT Equivalent, respectively.

Present-day model of lunar meteoroids and their impact flashes for LUMIO mission

The Lunar Meteoroid Impacts Observer (LUMIO) is a CubeSat mission to observe, quantify, and characterize the meteoroid impacts by detecting their flashes on the lunar farside. It complements lunar nearside observations performed by ground-based observatories to yield global information synthesis on the lunar meteoroid environment. Predicting LUMIO’s scientific outcome involves devising a methodology to model the meteoroid environment. We propose a method where numerous known meteoroid streams, as well as sporadic collisions with the lunar surface, are modeled. Impacts are generated with a stochastic approach based on experimental observations of fireballs, impact flashes, and meteors. A catalog collecting data of both meteoroid streams and sporadic background is made available to the community. Sample scenarios are reproduced to show the capabilities of our method. A synthesis of the statistical analysis performed on the collision dynamics is presented. Results show that a typical scenario counts almost 2 million impacts with impact kinetic energy larger than 10−7 kton TNT Equivalent, out of which approximately 200.000 fall in the energy range of interest for the LUMIO mission. For that subset, the equivalent black body temperature is estimated to range in 1510-2290K, the average impact flash duration is expected to be approximately 15ms, and the average plume area is predicted to be roughly 70m2.

PyNAPLE: Lunar Surface Impact Crater Detection

ABSTRACT In the last 20 yr, over 600 impact flashes have been documented on the lunar surface. This wealth of data presents a unique opportunity to study the meteoroid flux of the Earth–Moon environment, and in recent years the physical properties of the impactors. However, other than through serendipitous events, there has not been yet a systematic search and discovery of the craters associated to these events. Such a meteoroid-crater link would allow us to get insight into the crater formation via these live observations of collisions. Here, we present the pynaple (python NAC Automated Pair Lunar Evaluator) software pipeline for locating newly formed craters using the location and epoch of an observed impact flash. We present the first results from pynaple, having been implemented on the 2017-09-27 impact flash. A rudimentary analysis on the impact flash and linked impact crater is also performed, finding that the crater’s ejecta pattern indicates an impact angle between 10–30°, and although the rim-to-rim diameter of the crater is not resolvable in current LRO NAC images, using crater scaling laws we predict this diameter to be 24.1–55.3 m, and using ejecta scaling predict a diameter of 27.3–37.7 m. We discuss how pynaple will enable large scale analyses of sub-kilometer scale cratering rates and refinement of both scaling laws, and the luminous efficiency.

A low-dispersion spectral video camera for observing lunar impact flashes

An impact of a meteoroid on the lunar surface at speeds exceeding several kilometers per second generates a light flash generally less than 0.1 s in duration. We made a simple spectral video camera for observing the lunar impact flashes and monitored the waxing crescent Moon’s non-sunlit surface from Oct. 2016 to May 2017. We detected ten flash candidates though there was no report of simultaneous detections by other observers. We obtained low-dispersion spectra in visible wavelengths for nine of them. Six of them show spectra similar to those of the flashes observed during the Geminids meteor activity in Dec. 2018 by the same camera. The spectra are continuous and red. Blackbody spectra fitted to them show temperatures around 3000 K. On the other hand, three of them show continuous blue spectra. Blackbody spectra fitted to them show temperatures of more than 6000 K. Specular reflection of sunlight by space debris might lead to these flashes. However, the impact of a low-density meteoroid not against the fine lunar regolith but solid lunar rocks could cause blue flashes. In this paper, we give full details of the camera and the analytical procedures of the videos. We also discuss recommendations for future spectral observations.Graphical

Gamma-ray emission from supermassive black hole binary OJ 287

OJ 287 is one of the most studied BL Lacs with very long optical measurements which spectrum has been well measured through radio to X-rays. OJ 287 is supposed to be a binary black hole system. Its secondary black hole passes the accretion disk of the primary black hole and produces two impact flashes per 12-year period. Observations of OJ 287 in the GeV – TeV energy range reveal the variable γ-ray flux connected with the flare activity of this object. The spectral energy distributions of BL Lac objects consist of two broad peaks. The Inverse Compton emission of the relativistic electrons in the jet or combined with an external Compton mechanism are considered in the leptonic scenario of second, higher frequency spectrum part generation. The last one supposes the existence of the external to jet photon cloud. Also, the second spectrum part is supposed to be generated due to the acceleration of the cosmic ray hadrons in expanding shock produced by outflow, which then collides with the wind of the primary black hole. The detection of GeV – TeV energy fluxes can help find the configuration parameters of the two-black hole system.

Impacts on the Moon: Analysis methods and size distribution of impactors

We are preparing a telescope system to carry out a survey of detection and analysis of lunar impact flashes. In the framework of this project, here we present all necessary methods to automatically identify these luminous events, their lunar impact coordinates, the origin of the impacting meteoroids, as well as the estimation of their physical properties such as mass and size. We tested our methods against confirmed impact events and constructed the meteoroid size frequency distribution of impactors using literature data of the last 20 years. In addition, we present the first lunar impact event observed from the Observatoire de la Côte d’Azur that was detected during the testing phase of our project.

Low dispersion spectra of lunar impact flashes in 2018 Geminids

Lunar impact flashes have been observed at collisions of meteoroids against the non-sunlit lunar surface at speeds exceeding 10 ​km ​s−1. We detected 13 flash candidates between 6.2 and 9.9 in R-magnitude on December 15, 2018 during the Geminids meteor activity. Two or three observatories confirmed eleven of them. We obtained their spectra in the wavelength range between 400 and 870 ​nm. They are continuous and red, with best-fitted single blackbody spectra indicating the temperatures of about 2000–4000 ​K. The temperatures for a few successive movie frames at 16 ​ms or 25 ​ms intervals decrease with time. Incandescent ejecta, consisting of melt droplets or dust, and the radiant floor of an impact crater could be the source of these flashes, except for the initial stages. At the beginning of some flashes, we found an excess of fluxes at short wavelengths of less than about 600 ​nm. The composites of two blackbody spectra may fit the spectra better where their temperatures are about 2000 K and 6000 ​K. The contribution of a high-temperature vapor plume, generated at the very beginnings of the impact phenomena, could be important.

Impact flash evolution of CO2 ice, water ice, and frozen Martian and lunar regolith simulant targets

AbstractThe wavelength dependence and temporal evolution of the hypervelocity impact self‐luminous plume (or “flash”) from CO2 ice, water ice, and frozen Martian and lunar regolith simulant targets have been investigated using the Kent two‐stage light‐gas gun. An array of 10 band‐pass filtered photodiodes and a digital camera monitored changes in the impact flash intensity during the different phases of the emitting ejecta. Early‐time emission spectra were also recorded to examine short‐lived chemical species within the ejecta. Analyses of the impact flash from the varied frozen targets show considerable differences in temporal behavior, with a strong wavelength dependence observed within monitored near‐UV to near‐IR spectral regions. Emission spectra showed molecular bands across the full spectral range observed, primarily due to AlO from the projectile, and with little or no contribution from vaporized metal oxides originating from frozen regolith simulant targets. Additional features within the impact flash decay profiles and emission spectra indicate an inhomogeneity in the impact ejecta composition. A strong correlation between the density of water ice‐containing targets and the impact flash rate of decay was shown for profiles uninfluenced by significant atomic/molecular emission, although the applicability to other target materials is currently unknown. Changes in impact speed resulted in considerable differences in the temporal evolution of the impact flash, with additional variations observed between recorded spectral regions. A strong correlation between the impact speed and the emission decay rate was also shown for CO2 ice targets. These results may have important implications for future analyses of impact flashes both on the lunar/Martian surface and on other frozen bodies within the solar system.

NELIOTA: Methods, statistics, and results for meteoroids impacting the Moon

Context. This paper contains results from the first 30 months of the NELIOTA project for near-Earth objects and meteoroids impacting the lunar surface. We present our analysis of the statistics concerning the efficiency of the campaign and the parameters of the projectiles and those of their impacts. Aims. The parameters of the lunar impact flashes are based on simultaneous observations in two wavelength bands. They are used to estimate the distributions of the masses, sizes, and frequency of the impactors. These statistics can have applications in both space engineering and science. Methods. The photometric fluxes of the flashes are measured using aperture photometry and their apparent magnitudes are calculated using standard stars. Assuming that the flashes follow a black body law of irradiation, the temperatures can be derived analytically, while the parameters of the projectiles are estimated using fair assumptions on their velocity and luminous efficiency of the impacts. Results. There have been 79 lunar impact flashes observed with the 1.2 m Kryoneri telescope in Greece. The masses of the meteoroids range between 0.7 g and 8 kg, and their respective sizes between 1 and 20 cm, depending on their assumed density, impact velocity, and luminous efficiency. We find a strong correlation between the observed magnitudes of the flashes and the masses of the meteoroids. Moreover, an empirical relation between the emitted energies of each band has been derived, allowing for an estimation of the physical parameters of the meteoroids that produce low energy impact flashes. Conclusions. The NELIOTA project has so far the highest detection rate and the faintest limiting magnitude for lunar impacts compared to other ongoing programs. Based on the impact frequency distribution on the Moon, we estimate that sporadic meteoroids with typical masses less than 100 g and sizes less than 5 cm enter the mesosphere of the Earth with a rate of ~108 meteoroids h−1 and also impact Moon with a rate of ~8 meteoroids h−1.

Development of On-board Image Processing Algorithm to Detect Lunar Impact Flashes for DELPHINUS

Development of On-board Image Processing Algorithm to Detect Lunar Impact Flashes for DELPHINUS

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

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.

Space-based Observation of Lunar Impact Flashes

Space-based Observation of Lunar Impact Flashes

NELIOTA: The wide-field, high-cadence, lunar monitoring system at the prime focus of the Kryoneri telescope

We present the technical specifications and first results of the ESA-funded, lunar monitoring project “NELIOTA” (NEO Lunar Impacts and Optical TrAnsients) at the National Observatory of Athens, which aims to determine the size-frequency distribution of small near-Earth objects (NEOs) via detection of impact flashes on the surface of the Moon. For the purposes of this project a twin camera instrument was specially designed and installed at the 1.2 m Kryoneri telescope utilizing the fast-frame capabilities of scientific Complementary Metal-Oxide Semiconductor detectors (sCMOS). The system provides a wide field-of-view (17.0′ × 14.4′) and simultaneous observations in two photometric bands (RandI), reaching limiting magnitudes of 18.7 mag in 10 s in both bands at a 2.5 signal-to-noise ratio (S/N) level. This makes it a unique instrument that can be used for the detection of NEO impacts on the Moon, as well as for any astronomy projects that demand high-cadence multicolor observations. The wide field-of-view ensures that a large portion of the Moon is observed, while the simultaneous, high-cadence, monitoring in two photometric bands makes possible the determination of the temperatures of the impacts on the Moon’s surface and the validation of the impact flashes from a single site. Considering the varying background level on the Moon’s surface we demonstrate that the NELIOTA system can detect NEO impact flashes at a 2.5 S/N level of ∼12.4 mag in theI-band andR-band for observations made at low lunar phases (∼0.1). We report 31 NEO impact flashes detected during the first year of the NELIOTA campaign. The faintest flash was at 11.24 mag in theR-band (about two magnitudes fainter than ever observed before) at lunar phase 0.32. Our observations suggest a detection rate of 1.96 × 10−7events km−2h−1.

NELIOTA: First temperature measurement of lunar impact flashes

We report the first scientific results from the NELIOTA (NEO Lunar Impacts and Optical TrAnsients) project, which has recently begun lunar monitoring observations with the 1.2-m Kryoneri telescope. NELIOTA aims to detect faint impact flashes produced by near-Earth meteoroids and asteroids and thereby help constrain the size-frequency distribution of near-Earth objects in the decimeter to meter range. The NELIOTA setup, consisting of two fast-frame cameras observing simultaneously in theRandIbands, enables – for the first time – direct analytical calculation of the flash temperatures. We present the first ten flashes detected, for which we find temperatures in the range ~1600 to 3100 K, in agreement with theoretical values. Two of these flashes were detected on multiple frames in both filters and therefore yield the first measurements of the temperature drop for lunar flashes. In addition, we compute the impactor masses, which range between ~100 g and ~50 kg.

Detectability of possible space weather effects on Mars upper atmosphere and meteor impacts in Jupiter and Saturn with small telescopes

Amateur astronomers operating small telescopes accumulate a larger amount of observational time of Solar System planets than the ensemble of professional telescopes. Over the last 15 years, advancements in low-cost fast acquisition cameras and image software processing tools have pushed forward the scientific analysis of these observations thanks to a sustained increase in quality and spatial resolution. The high temporal coverage attained by amateur astronomers collaborating with scientists allows detecting rare events in the atmospheres of different planets. In particular, high-atmosphere phenomena in Mars, possibly caused by solar activity, and meteor impacts in Jupiter have been observed serendipitously in the last decade. Here we review the contribution of amateur astronomers to these two fields. Coronal Mass Ejections arriving to Mars under favorable observing conditions can be predicted after observations of the Sun, and their possible effect on Mars upper atmosphere can be monitored with small telescopes. Impacts in Jupiter of two different classes can be discovered by amateur astronomers: intermediate size impacts big enough to leave a debris field on its atmosphere (150-m size objects before the impact), and fireballs caused by objects of 5–20 m producing short-lived flashes in video observations of the planet. In this regard, we present a software tool designed to analyze video observations of Jupiter and Saturn that should help to find new impact flashes on the giant planets.