Physical Properties of Near-Earth Asteroids (original) (raw)
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The threat of NEAs and the origin of terrestrial planets´ impactors
2013
The Near-Earth Asteroids (NEAs) are relatively small celestial bodies with perihelion distances of less than 1.3 au. They can have impacts with the terrestrial planets and therefore they are a permanent danger for the Earth and some of them are also called Potential-Hazardous Asteroids, PHAs. In this work some of the possible sources of NEAs are analysed in detail. In particular we analyse two asteroid groups, the Hungarias and the Vestians from the Main Belt region (asteroids from between the orbits of Mars and Jupiter), and the inner region of the Centaurs, bodies between the orbits of Jupiter and Saturn. In addition a photometrical study of an important approaching comet, C/2012 S1 ISON, plus some hints on its orbits, close encounters and some physical constraints, i.e. the encounter velocity, are presented. Furthermore, another work on the origin of a paleo-impact event, namely the Bosumtwi crater one, is studied. One of the main parts of this thesis is devoted to the dynamical ...
Astronomy and Astrophysics, 2010
Aims. We analyse a significantly large sample of spectroscopic data to provide a compositional characterization of the near-Earth asteroid population. We present visible and near-infrared spectra of a total of 74 near-Earth asteroids (NEAs) and Mars-crossers (MCs), covering the wavelength region from 0.5 to 2.5 μm. Using spectra of NEAs from other databases to enlarge our sample, and compiling two comparison samples of main belt asteroids (MBs) and ordinary chondrites (OCs), we analyse a total of 79 NEAs, 91 MBs, and 103 OCs. Methods. We obtained our visible and near-infrared spectra using the instruments and the telescopes located at "El Roque de los Muchachos" Observatory, in the island of La Palma (Spain). We compute several diagnostic spectral parameters from the reflectance spectra of NEAs, MBs, and OCs, that are used to infer the mineralogical composition. The distribution of the obtained values are analysed in 2 different parameter spaces. We also apply a robust statistical method based on neuronal networks to those spectral parameters, to compare the NEAs with OCs. Space weathering effects and dynamical and physical properties of NEAs and MBs are also studied. Results. Compositional differences between MBs and NEAs are inferred from the mineralogical analysis. The most remarkable results are: (1) the high olivine content of the NEAs; (2) the compositional similarity between NEAs and a small group of meteorites, the LL ordinary chondrites; and (3) that NEAs are not compositionally similar to OCs, implying that they are not the most likely parent bodies of those meteorites, as has been widely believed. To explain their apparently fresh surfaces (NEAs are on average less red than MBs), a combination of composition and size distribution (NEAs have diameters of some kilometres) should be invoked. Dynamical models applied to our sample of NEAs indicate that most of them originate in the inner part of the main belt, as expected.
Physical properties of near-Earth objects
Asteroids III, 2002
The population of near-Earth objects (NEOs) contains asteroids, comets, and the precursor bodies for meteorites. The challenge for our understanding of NEOs is to reveal the proportions and relationships between these categories of solar-system small bodies and their source(s) of resupply. Even accounting for strong bias factors in the discovery and characterization of higheralbedo objects, NEOs having S-type spectra are proportionally more abundant than within the main asteroid belt as a whole. Thus, an inner asteroid belt origin (where S-type objects dominate) is implied for most NEOs. The identification of a cometary contribution within the NEO population remains one of a case-by-case examination of unusual objects, and the sum of evidence suggests that comets contribute at most only a few percent of the total. With decreasing size and younger surfaces (due to presumably shorter collisional lifetimes for smaller objects), NEOs show a transition in spectral properties toward resembling the most common meteorites, the ordinary chondrites. Ordinary chondritelike objects are no longer rare among the NEOs, and at least qualitatively it is becoming understandable why these objects comprise a high proportion of meteorite falls. Comparisons that can be performed between asteroidal NEOs and their main-belt counterparts suggest that the physical properties (e.g., rotation states, configurations, spectral colors, surface scattering) of NEOs may be representative of main-belt asteroids (MBAs) at similar (but presently unobservable) sizes.
Statistical survey and analysis of photometric and spectroscopic data on NEAS
arXiv: Earth and Planetary Astrophysics, 2016
Studies on Near Earth Asteroids (NEAs) throw light on discoveries, identification, orbit prediction and civil alert capabilities, including potential asteroid impact hazards. Due to various new observational programs, the discovery rate of NEAs has drastically increased over the last few years. In this paper we present the statistical survey and analysis of fundamental parameters (derived from Photometric and Spectroscopic observations) of a large sample of NEAs from various databases like IAU Minor Planet Center, European Asteroid Research Node (E.A.R.N.), Near Earth Objects - Dynamic Site (NEODyS- 2), M4AST and SMASSMTT portals. We also discuss the characterization of NEAs on the basis of the correlations between theparametersstudied from different observationsand theirphysical implicationsin understanding the nature and physical properties of these objects. Keywords: NEOs; Apollo; Amor; Aten; Observations: Photometric, Spectroscopic.
Astronomy and Astrophysics Supplement Series, 1997
The results from photometric lightcurve observations of nine M-type asteroids are presented. New rotation periods were determined for 6 asteroids: 217 Eudora (12.54 h), 322 Phaeo (17.56 h), 572 Rebekka (5.65 h), 757 Portland (6.58 h), 857 Glasenappia (8.23 h) and 872 Holda (7.20 h). B − V colour measurements of seventeen previously unclassified asteroids add seven asteroids to the known M-type population.
Origin and evolution of near-Earth objects
Asteroids and comets on orbits with perihelion distance q < 1.3 AU and aphelion distance Q > 0.983 AU are usually called near-Earth objects (NEOs). It has long been debated whether the NEOs are mostly of asteroidal or cometary origin. With improved knowledge of resonant dynamics, it is now clear that the asteroid belt is capable of supplying most of the observed NEOs. Particular zones in the main belt provide NEOs via powerful and diffusive resonances. Through the numerical integration of a large number of test asteroids in these zones, the possible evolutionary paths of NEOs have been identified and the statistical properties of NEOs dynamics have been quantified. This work has allowed the construction of a steady-state model of the orbital and magnitude distribution of the NEO population, dependent on parameters that are quantified by calibration with the available observations. The model accounts for the existence of ~1000 NEOs with absolute magnitude H < 18 (roughly 1 km in size). These bodies carry a probability of one collision with the Earth every 0.5 m.y. Only 6% of the NEO population should be of Kuiper Belt origin. Finally, it has been generally believed that collisional activity in the main belt, which continuously breaks up large asteroids, injects a large quantity of fresh material into the NEO source regions. In this manner, the NEO population is kept in steady state. The steep size distribution associated with fresh collisonal debris, however, is not observed among the NEO population. This paradox might suggest that Yarkovsky thermal drag, rather than collisional injection, plays the dominant role in delivering material to the NEO source resonances.
Maria's Family: Physical Structure and Possible Implications for the Origin of Giant NEAs
Icarus, 1997
point of view of the origin of near-earth asteroids (NEAs) and meteorites. This is due to the fact that many families An extensive analysis of the Maria family is presented. A reconstruction of the original ejection velocity field of the frag-are located close to some of the main mean-motion and ments suggests that a substantial number of relatively large secular resonances within the belt. These resonances, like fragments may have been injected into the neighboring 3/1 the 3/1 mean-motion resonance with Jupiter and the 6 mean motion resonance with Jupiter. This also agrees with an secular resonance, are known to be efficient dynamic analysis of the size distribution of the family, suggesting that routes to the inner Solar System (Wisdom, 1983(Wisdom, , 1985, about 10 objects in the size range 15-30 km have probably Farinella et al. 1993b, 1994b. As a been lost. As a consequence, Maria's family can be seen as one consequence, it is plausible to assume that catastrophic of the most promising candidates for the source of the ''giant' ' disruptions that occurred in the neighborhood of the reso-
Research of a solid part of interplanetary matter in the Centre of Space Research
Implemented project of the Space Research Center develops in two separate projects with ITMS codes 26220120009 and 26220120029 (hereafter referred to as the first and the second phase of CKV) to date the most promising directions of research with implications for the environment and human liferesearch of the Sun, solar-terrestrial relations and research of a solid component of interplanetary matter in the vicinity of the Earth's orbit. In the research of interplanetary matter projects are studying physics and dynamics of small Solar System bodies, including bodies potentially dangerous for collision with Earth, studying the dust component entering the Earth's atmosphere with rare impacts on the Earth's surface. In the first phase of CKV we are creating station to obtain orbit data of meteors in the atmosphere. After completion of the video camera system, there will be possible to determine meteor paths in the atmosphere and calculate the orbits of particles in the Solar System before entering the Earth's atmosphere. System will be realised at the Skalnaté Pleso Observatory. In the frame of the second phase of CKV an automatic bolide observatory will be purchased, which will be used for bolide studies at Lomnický Peak or Stará Lesná. A major modernization of the observatory for obtaining data on the solid component of interplanetary matter in particular to the Near Earth Asteroids (NEA) will be realised by construction of a robotic reflector with a primary mirror of 1.2-1.3 meters in diameter to discovering, photometry and spectroscopy of NEA. The telescope will be located in an existing robotic dome at the Skalnaté Pleso Observatory.