The objective of this paper is to carry out periodic orbital propagation and bifurcations detection around asteroid 433 Eros. Specifically, we propose to exploit a frequency-domain method, the harmonic balance method, as an efficient alternative to the usual time integration. The stability and bifurcations of the periodic orbits are also assessed thanks to the Floquet exponents. Numerous periodic orbits are found with various periods and shapes. Different bifurcations, including period doubling, tangent, real saddle and Neimark-Sacker bifurcations, are encountered during the continuation process. Resonance phenomena are highlighted as well.

The surfaces of most of the atmosphereless solar system bodies are referred to as regolith or layers of usually loosely connected fragmentary debris, produced by meteorite impacts. Measurement of light scattered from such surfaces provide information about the composition and structure of the surface. In the present work, the effect of porosity and particle size, on reflectance is studied for regolith like samples. For modelling the experimental data Hapke 2008 is used and found to be in good agreement with laboratory data. From the present study, it can be concluded that the physical properties of a regolith, such as porosity, particle size etc are effectively represented by albedo.

The population size structure from a total of 876 individuals, together with published values of growth rate, maximum size and size at age were used to estimate an instantaneous rate of natural mortality (M) of 0.46–0.59 year−1 in a population of the sea star Archaster angulatus from south-western Australia. Peak abundance (17%) of all animals sampled was 105–109 mm arm radius (means of 4.2–4.8 years of age) and only one per cent of sea stars are predicted to live beyond 8 years in the population studied. There are few comparable studies on sea stars but when compared with rates of natural mortality in other echinoderms (sea urchins), A. angulatus is intermediate among species which exhibit the extremes of life history strategies, that is, those which grow very rapidly and may live just two years or less and those with very slow growth rates and which may live for decades.

We report a systematic spectroscopical investigation of three plagioclase particles (RB-QD04-0022, RA-QD02-0025-01, and RA-QD02-0025-02) returned by the Hayabusa spacecraft from the asteroid Itokawa, by means of scanning electron microscopy, cathodoluminescence microscopy/spectroscopy, and micro-Raman spectroscopy. The cathodoluminescence properties are used to evaluate the crystallization effects and the degree of space weathering processes, especially the shock-wave history of Itokawa. They provide new insights regarding spectral changes of asteroidal bodies due to space weathering processes. The cathodoluminescence spectra of the plagioclase particles from Itokawa show a defect-related broad band centered at around 450 nm, with a shoulder peak at 425 nm in the blue region, but there are no Mn- or Fe-related emission peaks. The absence of these crystal field-related activators indicates that the plagioclase was formed during thermal metamorphism at subsolidus temperature and extreme low oxygen fugacity. Luminescence characteristics of the selected samples do not show any signatures of the shock-induced microstructures or amorphization, indicating that these plagioclase samples suffered no (or low-shock pressure regime) shock metamorphism. Cathodoluminescence can play a key role as a powerful tool to determine mineralogy of fine-grained astromaterials.

Precise data from instrumental observations of fireballs, especially those for really bright bolides, provide information about the population and physical properties of meteoroids, i.e. fragments of asteroids and comets, colliding with the Earth's atmosphere. An overview of what is known about meteoroids and their parent bodies from analysis of bolides producing meteorite falls, especially from the instrumentally observed meteorite falls, was a topic of this invited contribution. At present, atmospheric and orbital information with different degree of reliability and precision for these meteorite falls is known for only 24 cases. This topic was described in detail in the review work of Borovička, Spurný and Brown (2015) (Borovička et al., 2015). However, this work contains all instrumentally documented falls until end of 2013. To bring this work up to date, two new instrumentally observed meteorite falls in 2014, the Annama meteorite fall in Russia on 18 April 2014 and the Žďár nad Sázavou meteorite fall in the Czech Republic on 9 December 2014, are presented and commented in this paper. Especially the second case is mentioned in more detail including still unpublished data. Statistical analyses resulting from all 24 instrumentally documented falls are also mentioned.

In the Bay of Douarnenez, in a reference area surveyed for echinoderms, the relative abundance of epifaunal ophiuroids (Ophiothrix fragilis and Ophiocomina nigra) was estimated by dredging and video surveys. Two surveys were undertaken in 2008 and 2011, following a protocol similar to that used in a long-term survey conducted in the 1980s. The data were then compared between the two periods. The present observations demonstrate a recolonization of this site by these ophiuroids, which had almost disappeared between 1983 and 1988. However, although the mean densities of Ophiothrix fragilis were similar to those found prior to this general ophiuroid decrease, Ophiocomina nigra densities were much greater. This latter species not only increased significantly in density and bottom coverage in the reference area, but also showed strong juvenile recruitments on maerl beds and colonization of other bottoms of the bay at very high densities according to a geostatistical analysis. Further studies would be necessary to establish whether or not there is a cause-and-effect relationship between the increase of green algae in the bay and the development of this opportunistic species.

We examined habitat, population size-structure, colour dimorphism, reproductive behaviour, arm loss and the relation between arm regeneration to pyloric caeca indices in populations at Whitford Rock (WR) and Port Beach (PB) in January 2009. The sediment was fine sand at WR and a mix of larger particles at PB. Individuals at PB were predominantly orange and more uniform in colour than those at WR, which were predominantly grey. Body size and pyloric caeca index of individuals at WR were greater than those of individuals at PB, indicating the nutritional condition was better at WR. This suggests the quantity or quality of food at WR was better. Organic matter of the pyloric caeca and body wall of intact and regenerating individuals at both sites were similar, indicating loss of an arm did not affect gross proximate composition of the organs. Sea stars with regenerating arms made up 5.4 and 8.4 % of the populations observed. Despite the very small size of the gonads, some individuals were in the pseudocopulatory position, indicating this behaviour occurs even when gametes are not present. In every case observed, the male of the pseudocopulating pair was situated above the female. Given the abundance of this species in nearshore habitats dominated by sediment, it is likely to be ecologically important. However much of the biology and ecology of the species, even its diet, remain unknown. This together with its unusual mode of reproductive behaviour involving pseudocopulation, which is only known from two other species of asteroids, underscore the need for more research on Archaster angulatus.

We present the visible spectrum of asteroid-comet transition object 133P/Elst-Pizarro (7968), the first member of the new population of objects called Main Belt Comets (Hsieh & Jewitt 2006). The spectrum was obtained with the 4.2m William Herschel Telescope at the “Roque de los Muchachos” observatory. The orbital elements of 133P place it within the Themis collisional family, but the observed cometary activity during it last 3 perihelion passages also suggest a possible origin in the trans-Neptunian belt or the Oort Cloud, the known sources of comets. We found a clear similarity between our spectrum of 133P and those of other members of the Themis family such as 62 Erato, and a strong contrast with those of cometary nuclei, such as 162P/Siding-Spring. This spectral comparison leads us to conclude that 133P is unlikely to have a cometary origin. This conclusion is strengthened by spectral similarities with activated near-Earth asteroid 3200 Phaethon, and suggest that there are activated asteroids in the near-Earth asteroid and main belt populations with similar surface properties.

New distribution information is given for three asteroid and one holothuroid species found in the eastern Pacific.

The dynamics of binary Near-Earth objects (NEO) are discussed and a simple model for the study of their dynamics is introduced. Main results on the motion and stability of binary asteroids are reviewed. The effect of perturbations external to the binary system, including solar gravity, solar radiation pressure, and planetary gravity, are considered.

The physical properties of NEOs and other asteroids are mostly obtained with photometry. The resulting models describe the shapes, spin states, scattering properties and surface structure of the targets, and are the solutions of inverse problems involving comprehensive mathematical analysis. We review what can and cannot be obtained from photometric (and complementary) data, and how all this is done in practice. The role of photometry will become completely dominating with the advent of large-scale surveys capable of producing calibrated brightness data. Due to their quickly changing geometries with respect to the Earth, NEOs are the population that can be mapped the fastest.

The population of Near-Earth Objects contains small bodies that can make very close passages to the Earth and the other planets. Depending on the approach distance and the object's internal structure, some shape readjustment or disruption may occur as a result of tidal forces. A real example is the comet Shoemaker Levy 9 which disrupted into 21 fragments as a result of a close approach to Jupiter, before colliding with the planet during the next passage in July 1994. We have recently developed an exact analytical theory for the distortion and disruption limits of spinning ellipsoidal bodies subjected to tidal forces, using the Drucker-Prager strength model with zero cohesion. This model is the appropriate one for dry granular materials such as sands and rocks, for rubble-pile asteroids and comets, as well as for larger planetary satellites, asteroids and comets for which the cohesion can be ignored. Here, we recall the general concept of this theory for which details and major results are given in a recent publication. In particular, we focus on the definition of “material strength”: while it has great implications this concept is often misunderstood in the community of researchers working on small bodies. Then, we apply our theory to a few real objects, showing that it can provide some constraints on their unknown properties such as their bulk density. In particular it can be used to estimate the maximum bulk density that a particular object, such as 99942 Apophis, must have to undergo some tidal readjustments during a predicted planetary approach. The limits of this theory are also discussed. The cases where internal cohesion cannot be ignored will then be investigated in the near future.

Of the nearly 3900 near-Earth asteroids (NEAs) known as of June 2006, 325 have estimated rotation periods, with most of those determined by lightcurve analysis led by a few dedicated programs. NEAs with diameters down to 10 meters have been sampled. Observed spin distribution shows a major changing point around diameter of 200 meters. Larger NEAs show a barrier against spins faster than 11 d−1 (period about 2.2 h) that shifts to slower rates (longer periods) with increasing lightcurve amplitude (i.e., with increasing equatorial elongation). The spin barrier is interpreted as a critical spin rate for bodies in a gravity regime; NEAs larger than 200 meters are predominantly bodies with tensile strength too low to withstand a centrifugal acceleration for rotation faster than the critical spin rate. The cohesionless spin barrier disappears at sizes less than 200 meters where most objects rotate too fast to be held together by self-gravitation only, so a cohesion is implied in the smaller NEAs.

The distribution of NEA spin rates in the cohesionless size range (D0.2 km) is highly non-Maxwellian, suggesting that mechanisms other than just collisions have been at work. There is a pile up just in front of the barrier, at periods 2–3 h. It may be related to a spin up mechanism crowding asteroids to the barrier. An excess of slow rotators is observed at periods longer than 30 hours. A spin-down mechanism has no obvious lower limit on spin rate; periods as long as tens of days have been observed.

Most NEAs appear to be in their basic spin states with rotation around principal axis with maximum moment of inertia. Tumbling objects (i.e., bodies in excited, non-principal axis rotation) are present and actually predominate among slow rotators with estimated damping timescales longer than the age of the solar system. A few tumblers observed among fast rotating coherent objects appear to be either more rigid or younger than the larger (cohesionless) tumblers.

An abundant population of binary systems has been found among NEAs. The fraction of binaries among NEAs larger than 0.3 km has been estimated to be 15 ± 4%. Primaries of binary systems concentrate at fast spin rates (periods 2–3 h) and low amplitudes, i.e., they lie just below the cohesionless spin barrier. The total angular momentum content in binary systems suggests that they formed from parent bodies spinning at the critical rate. The fact that a very similar population of binaries has been found among small main belt asteroids suggests a binary formation mechanism that may not be related to close encounters with the terrestrial planets.

The regular CCD observations of near-Earth asteroids (NEAs) in the Institute of Astronomy of Kharkiv National University were initiated in 1995 within the framework of asteroid hazard problem in collaboration with the DLR, Institute of Planetary Research (Berlin). The main aim of the study is a determination of rotation periods and shapes of NEAs as well as astrometry of newly discovered objects. We also carry out the absolute photometry of NEAs in BVRI bands in order to put constraints on surface properties and to estimate their diameters. The observations are carried out with 0.7-m telescope of the Institute of Astronomy (Kharkiv) and with 1-m telescope of the Crimean Astrophysical Observatory (Simeiz) in the standard Johnson-Cousins photometric system. Some observations were made as an optical support of radar observation of NEAs. We present the results of photometric observations of 21 NEAs obtained in 2004-2006 which include asteroid rotation properties, diameters and shapes.

We present an overview of our work on shape and spin state determination of asteroids from photometric data sparse in time. Our results are based on simulations that were performed using realistic shape and light-scattering models and time sequences that will be provided by Pan-STARRS (Panoramic Survey Telescope and Rapid Response System). We show some typical examples of physical model reconstruction of main belt and near-Earth asteroids and discuss the lightcurve inversion of slow and fast rotators, binary asteroids and tumbling asteroids. We emphasize the scientific potential of sparse photometric data to produce models of a large number of asteroids within the next few years.