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The issue of the presence of meter- and decameter-sized bodies in meteor and fireball streams is of fundamental importance in the context of the theory of disintegration of parent bodies. Our observations, which have been carried out since 1995, indicate that such bodies are present in the Perseid, α-Capricornid, Leonid, and Coma-Berenicid meteoric streams. A catalogue is presented here for the parameters of the detected bodies. The spatial density of the meter-sized bodies is estimated based on the observational material. Within the errors, our estimates agree with the estimates based on the extrapolation of meteor and fireball data. An analysis of the observations suggests some inferences on the structure of the streams under study. [ABSTRACT FROM AUTHOR]

The detection and study of spectral signs of sublimation-driven dust activity (SDA) in 20 primitive-type asteroids of the Main Belt observed in the visible range allowed us to ascertain its temporal (or periodic) character. The asteroids exhibit SDA of relatively low intensity at minimal heliocentric distances, when their subsolar temperatures are, accordingly, highest (i.e., the surface temperature of the asteroid at the center of its sunlit hemisphere is close to the absolute maximum). Most likely, the major cause of SDA in these asteroids is that their interior contains H2O ice, which becomes outcropped due to recent impact events. As follows from the numerical modeling of the reflectance spectra of active asteroids under consideration, the optically thin dust exosphere (DE), which was induced by SDA and envelopes these bodies, consists of submicron homogeneous particles of different composition and/or fractal-like aggregates of such particles. Taking into account an extremely weak gravitational field of asteroids that cannot hold this optically thin DE even for a short time (especially, if their sizes are less than ~10 km), we conclude that the DE of active primitive-type asteroids is supported by two jointly operating mechanisms. Namely, the electrostatic field of photoemission nature creates a plasma–dust sheath on a sunlit side of the asteroid (as in all atmosphereless celestial bodies), and SDA provides the additional ejection of dust particles from the surface into this layer, which enhances their amount to a detectable level; at the same time, the self-rotation of the body contributes to the spreading of dust around the asteroid. [ABSTRACT FROM AUTHOR]

This paper presents the results that confirm the sublimation activity at the perihelion of the primitive main-belt asteroids 779 Nina, 704 Interamnia, and 145 Adeona; this activity was first discovered in September 2012 (Busarev et al., 2015; Busarev et al., 2016). The new spectrophotometric and/or UBVRI photometric observations of Nina, Interamnia, and Adeona were carried out in 2016–2018 during a regular perihelion passage of these asteroids. Additionally, probable spectral signs of weak sublimation activity were discovered on another two primitive main-belt asteroids, 51 Nemausa and 65 Cybele. In this study, we discuss the conditions for the occurrence of a periodic and/or continuous sublimation process on main-belt asteroids with low-temperature mineralogy; in particular, the conditions that are associated with their formation close to the "snow line" or beyond. We also consider general evolution processes that are able sustain a sufficiently high concentration of water ice close to the surface of the bodies in question and, therefore, their continuous sublimation activity, or lead to the recurrence of extinct activity. [ABSTRACT FROM AUTHOR]

In December 2020, at the 2-m telescope of the Terskol branch of the Institute of Astronomy, we carried out spectrophotometric observations in the range of ~0.36–0.95 μm of nine asteroids of the Main Belt (19 Fortuna, 52 Europa, 102 Miriam, 177 Irma, 203 Pompeja, 250 Bettina, 266 Aline, 379 Huenna, and 383 Janina), which were near perihelia of their orbits with significant eccentricities, in order to determine the effect of maximum subsolar temperatures on them. The study of the reflecance spectra of asteroids showed that the mineralogy of their matter is low-temperature and basically corresponds to the previously established classification (Tholen, 1989; Bus and Binzel, 2002). But in the spectra of eight asteroids (with the exception of 102 Miriam), for the first time, significant deviations were found that go beyond the spectral boundaries of their taxonomic types in the absence of noticeable changes in the spectral transparency of the Earth's atmosphere at time intervals shorter and longer than the exposure time. Such features can be interpreted as light scattering by a mobile (or inhomogeneous) dusty exosphere that forms near these asteroids near perihelion in the process of ice sublimation at the highest subsolar temperatures. In addition, as follows from the data obtained from the GOES-16 and SOHO satellites, the considered asteroids at the end of November 2020 (10 days before the start of our observations) were affected by a strong solar flare in the X-ray range, and then by a shock wave in solar wind caused by a coronal mass ejection on the Sun, which was quasi-synchronous with the X-ray flare. This probably led to an additional increase in the sublimation activity of the asteroids and manifestations of a derivative dusty exosphere. [ABSTRACT FROM AUTHOR]