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Register a new userNELIOTA: First temperature measurement of lunar impact flashes
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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 the $R$ and $I-$bands, enables - for the first time - direct analytical calculation of the flash temperatures. We present the first 10 flashes detected, for which we find temperatures in the range ~1,600-3,100 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.
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Kepler-96 is an active solar-type star harbouring a Super-Earth planet in close orbit. Its age of 2.3 Gyr is the same as the Sun when there was a considerable increase of oxygen in Earths atmosphere due to micro-organisms living in the ocean. We present the analysis of superflares seen on the transit lightcurves of Kepler-96b. The model used here simulates the planetary transit in a flaring star. By fitting the observational data with this model, it is possible to infer the physical properties of the flares, such as their duration and the energy released. We found 3 flares within the energy range of superflares, where the biggest superflare observed was found to have an energy of 1.81$times$10$^{35}$ ergs. The goal is to analyse the biological impact of these superflares on a hypothetical Earth in the habitable zone of Kepler-96 assuming this planet has protection via different scenarios: an Archean and Present-day atmospheres. Also, we compute the attenuation of the flare UV radiation through an Archean ocean. The conclusion is that considering the increase in the UV flux by the strongest superflare emission, {it E. Coli} and {it D. Radiodurans} could survive on the surface of the planet only if there was an ozone layer present on the planet atmosphere. However, they could escape from the hazardous UV effects at a depth of 28m and 12m below the ocean surface, respectively. For smaller superflares contribution, {it D. Radiodurans} could survive in the surface even in an Archean atmosphere with no ozone.
The flashes from meteoroid impacts on the Moon are useful in determining the flux of impactors with masses as low as a few tens of grams. A routine monitoring program at NASAs Marshall Space Flight Center has recorded over 300 impacts since 2006. A selection of 126 flashes recorded during periods of photometric skies was analyzed, creating the largest and most homogeneous dataset of lunar impact flashes to date. Standard CCD photometric techniques were applied to the video and the luminous energy, kinetic energy, and mass are estimated for each impactor. Shower associations were determined for most of the impactors and a range of luminous efficiencies was considered. The flux to a limiting energy of 2.5E-6 kT TNT or 1.05E7 J is 1.03E-7 km-2 hr-1 and the flux to a limiting mass of 30 g is 6.14E-10 m-2 yr-1 at the Moon. Comparisons made with measurements and models of the meteoroid population indicate that the flux of objects in this size range is slightly lower (but within error bars) than flux at this size from the near Earth object and fireball population by Brown et al. 2002. Size estimates for the crater detected by Lunar Reconnaissance Orbiter from a large impact observed on March 17, 2013 are also briefly discussed.
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 $times$ 14.4) and simultaneous observations in two photometric bands (R and I), reaching limiting magnitudes of 18.7 mag in 10 sec in both bands at a 2.5 signal-to-noise 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, for the first time, the determination of the temperatures of the impacts on the Moons surface and the validation of the impact flashes from a single site. Considering the varying background level on the Moons surface we demonstrate that the NELIOTA system can detect NEO impact flashes at a 2.5 signal-to-noise level of ~12.4 mag in the I-band and R-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 the R-band (about two magnitudes fainter than ever observed before) at lunar phase 0.32. Our observations suggest a detection rate of $1.96 times 10^{-7}$ events $km^{-2} h^{-1}$.
We discuss here a lunar impact flash recorded during the total lunar eclipse that occurred on 2019 January 21, at 4h 41m 38.09 +- 0.01 s UT. This is the first time ever that an impact flash is unambiguously recorded during a lunar eclipse and discussed in the scientific literature, and the first time that lunar impact flash observations in more than two wavelengths are reported. The impact event was observed by different instruments in the framework of the MIDAS survey. It was also spotted by casual observers that were taking images of the eclipse. The flash lasted 0.28 seconds and its peak luminosity in visible band was equivalent to the brightness of a mag. 4.2 star. The projectile hit the Moon at the coordinates 29.2 +- 0.3 $^{circ}$S, 67.5 +- 0.4 $^{circ}$W. In this work we have investigated the most likely source of the projectile, and the diameter of the new crater generated by the collision has been calculated. In addition, the temperature of the lunar impact flash is derived from the multiwavelength observations. These indicate that the blackbody temperature of this flash was of about 5700 K.
We use numerical modeling to investigate the combined effects of impact velocity and acoustic fluidization on lunar craters in the simple-to-complex transition regime. To investigate the full scope of the problem, we employed the two widely adopted Block-Model of acoustic fluidization scaling assumptions (scaling block size by impactor size and scaling by coupling parameter) and compared their outcomes. Impactor size and velocity were varied, such that large/slow and small/fast impactors would produce craters of the same diameter within a suite of simulations, ranging in diameter from 10-26 km, which straddles the simple-to-complex crater transition on Moon. Our study suggests that the transition from simple to complex structures is highly sensitive to the choice of the time decay and viscosity constants in the Block-Model of acoustic fluidization. Moreover, the combination of impactor size and velocity plays a greater role than previously thought in the morphology of craters in the simple-to-complex size range. We propose that scaling of block size by impactor size is an appropriate choice for modeling simple-to-complex craters on planetary surfaces, including both varying and constant impact velocities, as the modeling results are more consistent with the observed morphology of lunar craters. This scaling suggests that the simple-to-complex transition occurs at a larger crater size, if higher impact velocities are considered, and is consistent with the observation that the simple-to-complex transition occurs at larger sizes on Mercury than Mars.
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