Group Of Asteroids Research Articles

Photometric evidence of the complicated structure of asteroid 4179 Toutatis

Abstract Asteroid 4179 Toutatis belongs to a group of asteroids undergoing close encounters with Earth. We discuss the problem of its binarity from the point of view of its photometrical features. Photometric observations of Toutatis were made at the Crimean Astrophysical Observatory during 1992–1993. The frequency analysis of brightness variability revealed many periods. It is likely that it consists of two components. It was supposed that the orbital period is equal to 7d.48, the period nearly 62 d might be caused by precession, spin periods of the components are 2d.85 and 1d.66, respectively. Within our error limit the peroid 7d.48 is in good accordance with the period 7d.35 found from radar observations, period 2d.85 is about half of the radar period 5d.41. Discussion of our photometric data suggests some signs of the existence of satellites.

Escape of asteroids from the Hecuba gap

The dynamics of the 2 1 mean-motion asteroidal resonance with Jupiter is studied by numerical integration of the equations of motion of the Sun-Jupiter-Saturn-asteroid system. The measurement of the fundamental asteroidal frequencies by means of Fourier and wavelet analyses allows us to construct the web of the secular, secondary and Kozai resonances inside the 2 1 - resonance boundaries. The structure of the phase space of the 2 1 resonance is discussed with emphasis on the acting depletion mechanisms due to presence of these inner resonances. Special attention is paid to the study of the middle-eccentricity depleted region. The importance of the great inequality of the Jupiter-Saturn system in the acceleration of the diffusion processes in this region is pointed out. The existence of a group of asteroids like (3789) Zhongguo, inside the 2 1 resonance, is also discussed.

PathogenicNocardia isolated from clinical specimens including those of AIDS patients in Thailand

Forty strains of nocardioform microorganisms were isolated as clinical specimens including several from AIDS patients in Thailand. Among them, 37 strains were found to belong to the genus Nocardia. Our identification studies revealed that most of the strains (25 strains) belong to the N. asteroides group, i.e., N. asteroides sensu stricto and N. farcinica. Three strains were identified as N. otitidiscaviarum and two strains N. brasiliensis. In addition, 7 strains of rare pathogenic N. transvalensis were also isolated.

The distribution of asteroid sizes and its significance

Eleven years ago, Hughes ( Mon. Not. R. astr. Soc. 199, 1149, 1982) gave the size distribution of 740 asteroids. This has now been updated using 1778 known asteroidal diameters. The mass distribution index of the large main-belt asteroids is now found to be 2.09 ± 0.10. A power law relationship has been obtained between the perihelion distance and the diameter of the smallest known asteroid in any group of asteroids that have a specific range of perihelion distance. This has been used, in conjunction with the size distribution function, to produce a “corrected” histogram of asteroidal perihelion distances in which the relative significance (in number) of the Trojan asteroids has been increased dramatically. It is also concluded that the mass of the asteroid belt, M A (g), is given by log M A = 26.21 (+1.4, −1.0).

Kirkwood Gaps and Resonant Groups

This paper is a short review of the dynamics of the asteroidal resonances as currently determined from maps and simulations over 106 – 107 years. The main recent results concern the extensive exploration of the phase space to determine domains of initial conditions leading to close approaches to the inner planets, the topological dynamics of the planar Sun-Jupiter-asteroid problem at very high eccentricities and the differences amongst 2/1 and 3/2 resonances able to explain the existence of a gap in the asteroidal belt at the 2/1 resonance and of a group of asteroids in the 3/2 resonance. Current results point to a confirmation of Wisdom's theory for the formation of the gaps by gravitational evolution and scattering by the inner planets.

The composition and origin of the C, P, and D asteroids: Water as a tracer of thermal evolution in the outer belt

We present results of an extensive laboratory and telescopic investigation of H 2O distribution among the low-albedo, outer belt asteroids (2.5–5.2 AU). The water distribution was determined by surveying asteroids in that region for the 3-ωm reflectance absorption of molecular H 2O and structural OH ions; the 3-ωm band is the spectral signature of meteorite and asteroid hydrated silicates. The 19 asteroids observed in the survey, augmented by earlier reflectance data, yielded 3-ωm band depth measurements that reflect the present outer belt H 2O distribution. Of the 32 C-class asteroids in this sample, 66% have hydrated silicate surfaces, evidence of a mild aqueous alteration episode early in solar system history. The C class is not a primitive asteroid group in the mineralogical sense, but its anhydrous members appear little altered, as do the P and D classes beyond 3.5 AU. In addition to this pronounced hydration state difference between Cs and the more distant Ps and Ds, hydrated silicate abundance declines gradually among the Cs from 2.5–3.5 AU. Coupled with the apparently anhydrous P and D surfaces, this points to an original outer belt asteroid composition of anhydrous silicates, water ice, and complex organic material. Early solar wind induction heating of proto-asteroids declined in intensity with heliocentric distance, and produced the observed radial decrease in hydrated silicate abundance. The mild thermal processing of outer belt asteroids is a continuation of the intense heating and differentiation that occurred sunward of 2.5 AU, and both events are consistent with the induction heating mechanism. Water ice may be preserved in the interiors of P and D objects, and in some larger Cs.

Mineralogical clues to the origins of asteroid dynamical families

The mineralogical composition of the parent bodies of the asteroid dynamical families is investigated by means of remote-sensing data. Tables of the correlation between the taxonomic types of Tholen and family membership lists of Hirayama, Brouwer, Arnold, Carusi and Massaro, Kozai, and Williams were prepared. These tables, supplemented by recent IR and radar results, suggest that while the larger, well-defined families are fragments of collisionally disrupted parent bodies, most of the smaller proposed families cannot have such an origin. The most probable explanations of this result are that most family lists were generated using excessively generous criteria, or that subtle unrecognized dynamical effects analogous to the Williams resonances selectively deplete some regions of the asteroid belt, leaving family-like asteroid groups in other regions.

Urey prize lecture: Chaotic dynamics in the solar system

Newton's equations have chaotic solutions as well as regular solutions. There are several physical situations in the solar system where chaotic solutions of Newton's equations play an important role. There are examples of both chaotic rotation and chaotic orbital evolution. Hyperion is currently tumbling chaotically. Many of the other irregularly shaped satellites in the solar system have had chaotic rotations in the past. This episode of chaotic tumbling could have had a significant effect on the orbital histories of these satellites. Chaotic orbital evolution seems to be an essential ingredient in the explanation of the Kirkwood gaps in the distribution of asteroids. The phase space boundary of the chaotic zone at the 3 1 mean-motion commensurability with Jupiter is in excellent agreement with the boundary of the observed population of asteroids. Chaotic trajectories at the 3 1 commensurability have the correct properties to provide a dynamical route for the transport of meteoritic material from the asteroid belt to Earth. There is a large chaotic zone at the 2 1 commensurability, where there is a Kirkwood gap, but the phase space near the Hilda group of asteroids at the 3 2 commensurability is dominated by quasiperiodic behavior. Chaotic trajectories in the 2 1 chaotic zone reach very high eccentricities by a path that temporarily takes them to high inclinations. The long-term evolution of Pluto is suspiciously complicated, but objective criteria have not yet indicated that the motion is chaotic.

Structure of cryptosin monohydrate – a new cardioactive glycoside

$C_{29}H_4O_{11}.H_20$, $M_r = 5 82.7$, orthorhombic, $P2_12_12_1$, a = 9.663 (5), b = 11.723 (1), $c = 25.626 (3)\AA$, Z = 4, $V = 2902.9 \AA^3$, $D_x = 1.33 Mg m^{-3}$, $\lambda (Cu K\alpha) = 1.5418 \AA$, $\mu = 0.9 mm^{-1}$, F(000) = 1248, T= 295 K, final R for 2273 observed reflections is 0.077. Cryptosin contains deoxyglucose, asteroid group and a lactone ring. The glucopyranose ring assumes a chair conformation. The steroid group shows the presence of an epoxy group unlike in other cardioactive compounds such as strophanthidin and digitoxigenin. The A/B and C/D ring junctions are cis as in other cardioactive steroids. The molecules pack in a network which contains three distinct hydrogen bonds.

Some peculiarities in the Asteroidal Belt

The analysis of the fine structure of the Asteroidal Belt evidenciates a group of asteroids next to the resonance 4/9 with Jupiter. In this group and in other groups associated to the Hirayama families there are indications that their orbital parameters can be represented by quantum numbers as defined here and in two of our previous works. Together with this the distribution of the eccentricities and inclinations of the orbital planes of short period comets and diverse type of asteroids indicates that they can be classified as objects with e > sin i and objects with e > sin i with a limit e = sin i which determinates geometrical properties of the orbits related with discrete states in the solar system. This study lets open the possibility of following studies in order to confirm the quantum characteristics of the Asteroidal Belt being these characteristics common to all the solar system and depending of the same fundamental constant of action per mass unit H0 = 1/2π φ0 × T0 (potential × time) because only a small part of all the available data in the Asteroid Belt is used here.

Structure of the 2:1 and 3:2 jovian resonances

The chaotic regions of the phase space in the vicinity of the 2:1 and 3:2 jovian resonances are identified by using a mapping technique derived from a second-order expansion of the disturbing function for the planar elliptical restricted three-body problem. It is shown that both resonances have extensive chaotic regions which in some cases can lead to large changes in the eccentricity of asteroid orbits. Although the 3:2 resonance is shown to be more chaotic than the 2:1 resonance, the existence of the Hilda group of asteroids and the Hecuba gap may be explained by distinct differences in the location of the high-eccentricity regions at each resonance. The problem of the convergence of the expansion of the disturbing function in the outer asteroid belt is also discussed.

The spin periods of masteroids

In an attempt to verify the suggestion by Harris and Burns (1979) that M-type asteroids in general have high spin rates we are currently involved in a programme of photoelectricUBV observations of M and CMEU asteroids. Recently we have thus determined rotation periods, light-curve amplitudes andUBV colour indices for the asteroids 201 Penelope and 250 Bettina, both of which are situated in the (C,M,E) domain of the two-colour diagram. The resulting periods are very short (cf., IAUC 3523 and 3527). In general, we find that both the M and CMEU asteroid groups appear to be characterized by fast rotations, large amplitudes and an avoidance of membership in Hirayama families.

On the character of evolution of orbits in the vicinity of the 1 : 3 Kirkwood gap

The character of orbital evolution for bodies moving near the if 1 : 3 commensurability with Jupiter was studied by model calculations for the time interval of ∼500 years. A comparison of oscillations of the orbital elements a, e, q and q′ is made for ensembles of bodies along three starting orbits in the vicinity of the sharp commensurability with Jupiter. These orbits are eccentric ones of low inclinations having perihelia near the Earth's orbit. Examples of a deceleration of the rate of orbital evolution near the sharp commensurability are revealed. The existence of a group of asteroids connected with the Kirkwood gap, i.e., being in a resonant motion with Jupiter, is suggested. A connection of asteroids 887 Alinda and 1915 Quetzalcoatl with this gap is confirmed.

Ries impact crater, southern Germany: search for meteoritic material

Twenty-three samples from the Ries crater, representing a wide range of shock metamorphism, were analyzed for seven siderophile elements (Au, Ge, Ir, Ni, Os, Pd, Re) and five volatile elements (Ag, Cd, Sb, Se, Zn). Taking Ir as an example, we found siderophile enrichments over the indigenous level of 0.015 ppb Ir occur in only eight samples. The excess is very modest; even the most enriched samples (a weakly shocked biotite gneiss and a metal-impregnated amphibolite) have Ir, Os corresponding to ~4 × 10 −4 C1 chondrite abundances. Of five flädle glasses analyzed only one shows excess Ir. Suevite matrix and vesicular glass have slight enrichment, but homogenous glass from the same rock does not. In flädle glasses, Ni and Se are strongly correlated and apparently reside in Ir, Os-poor Sulfides [pyrrhotite, chalcopyrite, pentlandite(?)]of terrestrial, probably sedimentary, origin. The Ir, Os and Ni enrichments of the metal-bearing amphibolite are compatible with chondritic ratios, but these are ill-defined because of uncertainty in Ni. In the other samples enriched in siderophiles Ir(Os), Ni and Se are mutually correlated; Ni Ir and Ni Os ~ 11 × C1 and are much higher than any chondritic ratios; Se Ni ~ 2 × C1 and suggests a sulfide phase, rather than metal may be the host of the correlated elements. Lacking a plausible local source, this material is apparently meteoritic in origin. The unusual elemental ratios, coupled with the very low enrichments, tend to exclude chondrites and most irons as likely projectile material. Of the achondrites, aubrites seem slightly preferable. Ratios of excess siderophiles in Ries materiel match tolerably those of an aubrite (possibly atypical) occurring as an inclusion in the Bencubbin meteorite, Australia. The Hungaria group of Mars-crossing asteroids may be a source of aubritic projectiles.

Radiometric diameter and albedo of the remarkable asteroid 1976AA

It is pointed out that the minor planet 1976AA discovered on January 7, 1976, is the first asteroid found with an orbital period of less than a year. A description is given of a study in which the diameter and the albedo of the asteroid were determined with the aid of infrared radiometry. It is concluded that on the basis of its albedo 1976AA can probably be classed with the stony group of asteroids.

Descriptive Survey of Families, Trojans, and Jetstreams

The word “group” is so general that I would like to suggest that here it is used in its most general way: a group of asteroids is a collection of minor planets that have some feature in common. If we agree on this use of the word “group,” then we can discern the following asteroidal groups:(1) Groups that have a dynamical cause:(a) Trojans(b) Commensurability groups:(i) Hungaria group(ii) Hilda group(iii) Thule(2) Groups that probably have no dynamical cause:(a) Hirayama families(b) Brouwer groups(c) Jetstreams

Mass of Jupiter Derived from the Motion of 52 Europa.

The minor planet 52 Europa is one of a group of asteroids having mean motions nearly double that of Jupiter, and as a consequence has a sizable perturbation in longitude with a period of about 66 yr. Analysis of 297 observations, extending over a 100-yr period, indicates a mass of Jupiter in reciprocal solar mass units of 1047.381+0.020 m.e. The coefficients of the correction to the mass of Jupiter, used in the equations of condition of a least-square analysis, were obtained in the following fashion. With the n-body numerical integration program of J. Schubart, two ephemerides of the minor planet were generated using two different values for the mass of Jupiter. The differences in the coordinates of the minor planet were then divided by the difference in the mass of Jupiter. It was found by utilizing additional integrations that the differences in the coordinates divided by the difference in the masses were linear over the range of masses used for Jupiter in the numerical integrations. It was also noted that the differential perturbations of Jupiter on the earth could be neglected. The generality of the method makes it suitable for use with any well-observed minor planet. The author will extend this investigation using minor planets 10, 24, and 31.

The Martian Surface

The Martian Surface

Groups of asteroids probably of common origin

Groups of asteroids probably of common origin

Groups of Asteroids probably of Common Origin

Groups of Asteroids probably of Common Origin