Photometry of the Didymos System across the DART Impact Apparition

On 2022 September 26, the Double Asteroid Redirection Test (DART) spacecraft impacted Dimorphos, the satellite of binary near-Earth asteroid (65803) Didymos. This demonstrated the efficacy of a kinetic impactor for planetary defense by changing the orbital period of Dimorphos by 33 minutes. Measuring the period change relied heavily on a coordinated campaign of lightcurve photometry designed to detect mutual events (occultations and eclipses) as a direct probe of the satellite’s orbital period. A total of 28 telescopes contributed 224 individual lightcurves during the impact apparition from 2022 July to 2023 February. We focus here on decomposable lightcurves, i.e., those from which mutual events could be extracted. We describe our process of lightcurve decomposition and use that to release the full data set for future analysis. We leverage these data to place constraints on the postimpact evolution of ejecta. The measured depths of mutual events relative to models showed that the ejecta became optically thin within the first ∼1 day after impact and then faded with a decay time of about 25 days. The bulk magnitude of the system showed that ejecta no longer contributed measurable brightness enhancement after about 20 days postimpact. This bulk photometric behavior was not well represented by an HG photometric model. An HG 1 G 2 model did fit the data well across a wide range of phase angles. Lastly, we note the presence of an ejecta tail through at least 2023 March. Its persistence implied ongoing escape of ejecta from the system many months after DART impact

Achievement of the Planetary Defense Investigations of the Double Asteroid Redirection Test (DART) Mission

NASA's Double Asteroid Redirection Test (DART) mission was the first to demonstrate asteroid deflection, and the mission's Level 1 requirements guided its planetary defense investigations. Here, we summarize DART's achievement of those requirements. On 2022 September 26, the DART spacecraft impacted Dimorphos, the secondary member of the Didymos near-Earth asteroid binary system, demonstrating an autonomously navigated kinetic impact into an asteroid with limited prior knowledge for planetary defense. Months of subsequent Earth-based observations showed that the binary orbital period was changed by –33.24 minutes, with two independent analysis methods each reporting a 1σ uncertainty of 1.4 s. Dynamical models determined that the momentum enhancement factor, β, resulting from DART's kinetic impact test is between 2.4 and 4.9, depending on the mass of Dimorphos, which remains the largest source of uncertainty. Over five dozen telescopes across the globe and in space, along with the Light Italian CubeSat for Imaging of Asteroids, have contributed to DART's investigations. These combined investigations have addressed topics related to the ejecta, dynamics, impact event, and properties of both asteroids in the binary system. A year following DART's successful impact into Dimorphos, the mission has achieved its planetary defense requirements, although work to further understand DART's kinetic impact test and the Didymos system will continue. In particular, ESA's Hera mission is planned to perform extensive measurements in 2027 during its rendezvous with the Didymos–Dimorphos system, building on DART to advance our knowledge and continue the ongoing international collaboration for planetary defense

Density, Porosity And Magnetic Susceptibility Of The Košice Meteorite Shower And Homogeneity Of Its Parent Meteoroid

Bulk and grain densities, porosities, and magnetic susceptibilities of 67 individuals of Košice H chondrite fall were measured. The mean bulk and grain densities were determined to be 3.43 g/cm3 with standard deviation (s.d.) of 0.11 g/cm3 and 3.79 g/cm3 with s.d. 0.07 g/cm3, respectively. Porosity is in the range from 4.2% to 16.1%. The logarithm of the apparent magnetic susceptibility (in 10-9 m3/kg) shows narrow distribution from 5.17 to 5.49 with mean value at 5.35 with s.d. 0.08. These results indicate that all studied Košice meteorites are of the same composition down to ~g scale without the presence of foreign (non-H) clasts and are similar to other H chondrites. Košice is thus a homogeneous meteorite fall derived from a homogeneous meteoroid. © 2014 Elsevier Ltd

Dust color variations of comet C/2016 M1 (PanSTARRS)

Our research aims to study the dust environment of comets that are active beyond the snow line. The current work considers dust color variations in the coma of long-period comet C/2016 M1 (PanSTARRS). We observed the comet from July to October 2017 (12 epochs) using a 0.61-m telescope at the Skalnaté Pleso Observatory. The activity of the comet was stable and typical for other long-period comets. Our data show a slight bluing of the comet S'BR = −0.5 ± 0.9% per 1000 Å on August 26 and reddening to S'BR = 6.0 ± 1.4% per 1000 Å on August 28, while during the rest of the observation period, the comet mostly had red color that is typical of other comets; i.e., the average S'BR is equal to 9.5 ± 1.1% per 1000 Å. We have performed modeling of the observed color variations using model agglomerated debris particles. We could reproduce the dust color variations through changes in the dust composition; however, photometric data on their own do not allow us to make a precise conclusion. For instance, the bluest color could be induced by either water-ice, Mg-rich silicate, amorphous carbon, or their mixture. The reddest color is consistent with Mg-Fe silicates and organics. Nevertheless, further study of the comet in terms of polarimetry would yield a more robust conclusion. © 202411Nsciescopu

Dust properties and their variations in comet C/2013 X1 (PANSTARRS)

Context. We analyze the results of photometric monitoring of comet C/2013 X1 (PANSTARRS) from December 2015 until January 2016 obtained within B, V, and R Johnson–Cousins filters. Aims. The main objective is to investigate the dust coma and to obtain the physical characteristics of its dust particles. Methods. We analyzed our observations using model-agglomerated debris particles, and we constrained the microphysical properties of the dust in comet C/2013 X1 (PANSTARRS) on the pre-outburst and post-outburst epochs. Moreover, we applied a geometrical model to the images processed by digital filters to estimate the rotational period of the nucleus. Results. Our campaign revealed a sharp increase in the comet brightness on January 1, 2016. The B − V and V − R colors calculated within an aperture size of 17 000 km appear to be mostly red, except for the outburst date. The dust production (A f ρ proxy) and normalized spectral gradient S′ (B − R) dramatically changed on January 2 as compared to what was seen in December 2015. According to this model, the C/2013 X1 coma was populated by 70% organic-matter particles by volume and by two types of silicate particles together, constituting the other 30%. One type of silicate particles was composed of Mg-rich silicates, whereas the other type was composed of both Mg-rich and Fe-poor silicates. Using the geometrical model, we estimate the nucleus rotational period to be (24.02 ± 0.02) h. We interpret the observed coma morphology by two jet structures, one structure that formed by the near-pole active area at a latitude of (85+5−3)°, and the other structure formed by an active area at a latitude of (+40 ± 5)°

Time and phase resolved optical spectra of potentially hazardous asteroid 2014 JO25

The asteroid 2014 JO25, considered to be "potentially hazardous" by the Minor Planet Center, was spectroscopically followed during its close-Earth encounter on 19th and 20th of April 2017. The spectra of the asteroid were taken with the low resolution spectrograph (LISA), mounted on the 1.2-m telescope at the Mount Abu Infrared Observatory, India. Coming from a region close to the Hungaria population of asteroids, this asteroid follows a comet-like orbit with a relatively high inclination and large eccentricity. Hence, we carried out optical spectroscopic observations of the asteroid to look for comet-like molecular emissions or outbursts. However, the asteroid showed a featureless spectrum, devoid of any comet-like features. The asteroid's light curve was analyzed using V band magnitudes derived from the spectra and the most likely solution for the rotation of the asteroid was obtained. The absolute magnitude H and the slope parameter G were determined for the asteroid in V filter band using the IAU accepted standard two parameter H-G model. A peculiar, rarely found result from these observations is its phase bluing trend. The relative B-V color index seems to decrease with increasing phase angle, which indicates a phase bluing trend. Such trends have seldom been reported in literature. However, phase reddening in asteroids is very common. The asymmetry parameter g and the single scattering albedo w were estimated for the asteroid by fitting the Hapke phase function to the observed data. The asteroid shows relatively large value for the single scattering albedo and a highly back scattering surface.by Venkataramani Kumar, Ganesh Shashikiran , Archita Rai, Marek Husárik, K. S.Baliyan and U.C. Josh