Study of photometric phase curve with new brightness model:refining phase function system parameters of asteroid(107) Camilla

We characterize the morphology of the photometric phase curve model of an asteroid with a threeparameter magnitude phase function H-G_1-G_2 system by considering the effect of brightness variation arising from a triaxial ellipsoid representing the asteroid's shape.Applying this new model and a Markov Chain Monte Carlo method,we refine the photometric phase curve of asteroid(107) Camilla and obtain its absolute magnitude H=7.026_(-0.054)~(+0.052) mag,and phase function parameters G_1=0.489_(-0.044)~(+0.043) and G_2=0.259_(-0.023)~(+0.023).Meanwhile,we also determine(107) Camilla's orientation of pole(74.1°_(-4.5°)~(+4.3°),50.2°_(-5.0°)~(+5.4°)with rotational period of 4.843928_(-0.000001)~(+0.000001)h,and axial ratios a/b=1.409_(-0.020)~(+0.020) and b/c=1.249_(-0.060)~(+0.063).Furthermore,according to the values of phase function parameters G_1 and G_2,we infer that asteroid(107)Camilla is an X-type asteroid.     

Lightcurves and Synodic Periods for Asteroids 1998 ST49, (13154) and (27529)

The first photometric observations of the near-Earth asteroid 1998 ST₄₉ and the main belt asteroids (13154) and (27529) are reported. The synodic rotation periods and amplitudes of the lightcurves are:

? 2.3017 h, 0.11 mag for 1998 ST₄₉;

? 2.98502 h, 0.18 mag for (13154);

? 4.1290 h, 0.51 mag for (27529).

The periods for the first two asteroids are unambiguous, while the period of 4.1570 h is not ruled out for the third asteroid. Despite fast rotations, none of the presented asteroids exhibited any sign of binarity. Lightcurves were obtained at Modra Observatory.     

Shapes and Pole Orientations of Asteroids (360) Carlova and (209) Dido

Several light-curves of asteroid (360) Carlova and (209) Dido in different epochs were analyzed to determine shapes and pole orientations by means of AM-method and least squares method. New values of a/b, b/c, λ _p and β _p for asteroid (360) Carlova were obtained, which are 1.52°, 1.5°, 120 ± 6° and 66 ± 7°, respectively. We report a first determination of the parameters of (209) Dido which are 1.3°, 1.1°, 221 ± 6° and 37 ± 3°, respectively.     

Near-infrared spectroscopy of 3:1 Kirkwood Gap Asteroids: (3760) Poutanen and (974) Lioba

A mineralogical assessment of 3:1 Kirkwood Gap Asteroids (3760) Poutanen and (974) Lioba, has been carried out from spectral data obtained May 21, 2008 (974) and May 25, 2009 (3760) UT using the NASA Infrared Telescope Facility. Results indicate (3760) Poutanen as a spinel-bearing asteroid. The spinel contained within this asteroid appears to be embedded in calcium aluminum inclusions (CAIs) much like that of the CV3 chondrite Allende. The preservation of the CAIs implies a lack of igneous processing and places further constraints on the heating that occurred within the early Solar System. This analysis suggests (3760) Poutanen originated in the general formation zone of the CV3 meteorites, but in a sub-region depleted in iron-rich matrix material and enriched in pyroxene-bearing clasts. Analysis of (974) Lioba indicates it is an S(IV) asteroid with a surface silicate assemblage consisting of olivine and orthopyroxene, (Fs_21(±5)Wo_8(±3)), consistent with measured band centers, (0.96 ± 0.01 μm; 1.95 ± 0.02 μm), and the band area ratio (0.59 ± 0.15). The location, delivery efficiency ((24.5%) Farinella, P., Gunczi, R., Froeschlé, Ch., Froeschlé, C. [1993]. Icarus 101, 174-187), calculated mineralogy, and BAR strongly suggest (974) Lioba is a plausible parent body for the LL- or L-ordinary chondrites.     

Radar detection of near-Earth Asteroids 1915 Quetzalcoatl, 3199 Nefertiti, 3757 (1982 XB), and 4034 (1986 PA)

We describe Arecibo (2380 MHz, 12.6 cm) Doppler-only radar detections of near-Earth Asteroids 1915 Quetzalcoatl, 3199 Nefertiti, 3757 (1982 XB), and 4034 (1986 PA) obtained between 1981 and 1989. Estimates of the echo spectral bandwidths, radar cross-sections, and circular polarization ratios of these objects constrain their sizes, radar albedos, surface roughnesses, taxonomic classes, rotation periods, and pole directions. Our radar constraints on the diameters of Quetzalcoatl and Nefertiti are most consistent with sizes determined using thermal-radiometry and the Fast Rotation Model (FRM); this consistency may indicate that these asteroids have surfaces of high thermal inertia (i.e., little or no regolith). Constraints on Quetzalcoatl's radar albedo rule out a “metallic M” classification. The radar constraints for Nefertiti are inconsistent with a rotation pole published by Kaasalainen et al. (2004, Icarus 167, 178). Our estimates of 1982 XB's size are consistent with previously published estimates. The radar bandwidth of 1986 PA places an upper bound of about 24 h on its rotation period.     

Asteroids with Satellites: Inventory, Properties, and Prospects for Future Discoveries

The population of binary asteroids numbers over 160 systems, and they can be found amongst near-Earth asteroids (NEAs), Main-Belt asteroids (MBAs), Jupiter Trojans, Centaurs and trans-Neptunian objects (TNOs). The discoveries have been made with space missions, radar observations, photometric lightcurves, and high resolution imaging from the ground and space. The properties of each population are widely different due to varying formation mechanisms and discovery techniques for each group. Future large-aperture telescopes will be capable of imaging both components for nearly all known systems and will drastically improve prospects for discovery of smaller and more tightly bound systems throughout the Solar System. The study of binary asteroids has provided valuable estimates on asteroid density and structure, a better understanding of the radiative YORP-effect, insights on catastrophic collisions, and may prove to be a key diagnostic for understanding the formation and evolution of the Kuiper Belt population.     

The First International Conference “Comets,Asteroids, Meteors,Meteorites, Astroblemes,and Craters (CAMMAC-1)”

The conference was held in Vinnitsa (Ukraine) from September 26 until October 2, 1999. It was devoted to minor bodies in the Solar System, to structures on the surfaces of planets and the Earth, as well as to craters and astroblemes. The CAMMAC-1 meetings were held in the M. Kotsyubinskii Vinnitsa Pedagogical University. About 80 representatives from 19 research organizations of 15 European cities attended the conference. Thirty-six oral papers and a number of poster papers were presented and discussed. Several new scientific results are evaluated in the resolution, and the most topical problems in the study of minor bodies and impact structures on the surfaces of the Earth and planets are formulated.     

Analysis of Orbital Characteristics and Evolution of Near-Earth Asteroids (10302) 1989 ML and (4660) Nereus

Near-Earth asteroids (10302) 1989 ML and (4660) Nereus have attracted much attention as candidates for the next generation of deep space explorations. In the study, the maximum Lyapunov exponent (MLE) and MEGNO (Mean Exponential Growth factor of Nearby Orbits) index are calculated after considering the effects of major objects in the Solar system, and the stabilities of these two asteroids are discussed. For each asteroid, 1000 clonal particles consistent with the observational uncertainties are generated from a multivariate normal distribution. Statistical results display probably emerging regions of each asteroid within 0.1 million years, and provide distributions of occurrence times in the phase space of semi-major axis versus eccentricity. We estimate the probability of close encounters and collisions between the asteroid and Earth or other planets. Furthermore, secular resonances, Kozai resonance, and mean motion resonances are analyzed for nominal orbits of the two asteroids. We conclude that 1989 ML is in the region dominated by mean motion resonances with terrestrial planets. The probability of close encounters with them is relatively small, therefore its orbit is relatively stable. Nereus is located in a region that can have close-encounters with the Earth, and it has an extremely unstable orbit.     

近地小行星(10302) 1989 ML和(4660) Nereus的轨道特征及演化分析

近地小行星(10302) 1989 ML和(4660) Nereus作为下一代深空探测的候选目标一直备受关注. 在考虑太阳系主要天体的动力学背景下, 通过计算最大Lyapunov指数(MLE)及MEGNO (Mean Exponential Growth factor of Nearby Orbits)指数讨论它们的稳定性. 同时, 对每个小行星, 在其观测误差范围内按多元正态分布各选取1000个克隆粒子, 通过统计分析显示这两个小行星在10万年内可能的运动范围, 给出半长径-偏心率空间中的出现次数分布图, 并统计小行星与地球或其他大行星之间的密近交汇及碰撞的概率. 此外还对这两个小行星的标称轨道进行长期共振、Kozai共振及平运动共振的动力学分析. 综上得出结论, 1989 ML处在平运动共振主导的区域, 发生密近交汇的概率较小, 从而其轨道相对较稳定; 而Nereus处在地球的密近交汇区域, 轨道极不稳定.     

Titan's surface: Search for spectral diversity and composition using the Cassini VIMS investigation

The surface composition of Titan is of great importance for understanding both the internal evolution of Titan and its atmosphere. The Visual and Infrared Mapping Spectrometer (VIMS) investigation on Cassini is observing Titan from 0.35 to 5.11 μm with spatial resolution down to a few kilometers during each flyby of the spacecraft as it orbits Saturn. Our search for spectral diversity using seven methane transmission windows in the near infrared suggests that spectrally distinct units exist on the surface of Titan and that most of the surface can be modeled using only a few distinct spectral units: water frost, CO₂ frost, atmospheric scattering, and an unknown material bright at 2 μm. A dark, spectrally neutral material is also implied. Use of an atmospheric scattering component with spectral mixing analysis may provide a method for partially removing atmospheric effects. In some locations, atmospheric scattering accounts for the majority of the signal. There are also small regions with unusual spectra that may be due to low signal and high noise and/or may be exotic materials of interest. Further, we searched within the methane windows for spectral features associated with Titan's surface. Only the 5-μm and, to a lesser extent, the 2-μm window provide a reasonable opportunity for this, as the shorter-wavelength windows are too narrow and the 2.8-μm window is cluttered with an unknown atmospheric constituent. We find evidence for only one spectral feature: near 4.92 μm for the 5-μm bright Tui Regio region. CO₂ frost with grains smaller than about 10 μm is the best candidate we have found so far to explain this absorption as well as the feature's spectral contrast between the 2.7- and the 2.8-μm atmosphere subwindows. This suggested CO₂ identification is supported by the presence of an endmember in the spectral mixture analysis that is consistent with CO₂ frost with large grain sizes. We find no other absorption features that are statistically significant, including those reported earlier by others. These results are consistent with but greatly extend our early analysis that treated only the Ta data set [McCord, T.B., et al., 2006a. Planet. Space Sci. 54, 1524-1539]. In the spectral feature search process, we explored in detail the noise characteristics of the VIMS data within the 5-μm window, which has generally very low signal (4-20 DN), due to the measurement conditions and low illumination levels. We find noise of nearly Gaussian statistics except for some erratic darks and noise spikes, and the data set seems generally well behaved. We present examples of our attempt to improve on the standard VIMS pipeline data calibration.     

Infrared spectroscopic observations of 69230 Hermes (1937 UB): possible unweathered endmember among ordinary chondrite analogs

We have obtained near-infrared (0.8-2.5 μm) spectra of Hermes (1937 UB) using the NASA Infrared Telescope Facility on Mauna Kea. We find Hermes to have spectral properties consistent with L/LL chondrites, with a strong visual similarity to Gaffey (1976, J. Geophys. Res. 81, 905) average L6 chondrites. We define a ratio of band areas (RBA) using the Modified Gaussian Method (MGM: Sunshine and Pieters, 1990, in: Lunar and Planetary Institute Conference Abstracts, p. 1223, 1993, J. Geophys. Res. 98, 9075) to quantify near-infrared asteroidal data lacking a visible component. Hermes has a spectrum nearly indistinguishable from (19356) 1997 GH3. Together, these asteroids represent new endmembers on the continuum of spectra from ordinary chondrite meteorites to large main-belt S-class asteroids. We discuss regolith effects that may be occurring on Hermes and other possible ordinary chondrite parent bodies, and constrain the albedo of Hermes to 0.4 or higher (effective diameter 650 m or smaller) if it has a regolith. This value for albedo/diameter is consistent with radar results.     

Asteroids 10 Hygiea, 135 Hertha,and 196 Philomela: Heterogeneity of the material from the reflectance spectra

The reflectance spectra of asteroids 10 Hygiea (C-type), 135 Hertha (M-type), and 196 Philomela (S-type) are obtained in a range of 0.40–0.91 μm with different time intervals. In this paper, the technique of the spectral measurements of asteroids is analyzed and the reflectance spectra of Hygiea, Hertha, and Philomela are interpreted. The main physical and chemical factors and processes influencing the spectral characteristics of asteroids are considered. It is determined that the spectra of Hertha and Hygiea contain variations exceeding the measurement errors several times at different relative rotation phases, whereas spectral variations of Philomela caused by its rotation hardly exceed the error limits. Most probably, these variations are caused by local manifestations of the impact metamorphism of the material of asteroids in serious impact events. Results show that, to determine the prevailing spectral type and the corresponding mineralogy of each asteroid, one should estimate and take into account the changes in its spectral characteristics for a time interval comparable to the rotation period.     

The United Kingdom Infrared Telescope Deep Impact observations: Light curve, ejecta expansion rates and water spectral features

We present results from the United Kingdom Infrared Telescope observations of the impact of Deep Impact with Comet 9P/Tempel 1, on July 4, 2005 UT. These observations were carried out in conjunction with the worldwide observing campaign co-ordinated by K.J. Meech [Meech, K.J., and 208 colleagues, 2005. Science 310, 265-269]. The UKIRT team was the first to observe and announce the successful impact. At 05:50:52 (±2.5 s) UT the visible camera that is used to guide the telescope on the comet showed the start of a rapid rise in intensity, such that the visible brightness of Tempel 1 approximately doubled in 70 s. After that time there was a steady increase in the visible flux from the comet until it reached a maximum around 35 min post-impact, at which point it was more than ten times its original intensity. From an average of the time to maximum brightness and the time to noticeable intensity decline, we deduce that the material ejected by the impact expanded with a range of velocities between ∼125 and ∼390 m/s. We also observed water emission lines in the spectral region from 2.8945 to 2.8985 μm. We noted several water lines, which are known to be pumped by sunlight. But there was a lower intensity spectral component, which we propose may result from solar heating of icy grains freshly exposed by the impact.     

Seyfert Galaxies: A Perspective with the Infrared Space Observatory (ISO)

We present data from the Infrared Space Observatory (ISO) of a complete set of Seyfert galaxies (Seyfert 1 and Seyfert 2) in a wavelength range seldom explored so far. These data allow a detailed study of the far IR Spectral Energy Distribution of these sources. A Bayesian inversion method has been used to invert the Spectral energy Distribution (SED) of these sources yielding two fundamental results, namely that the far IR SED of Seyfert Galaxies can be explained solely through thermal reradiation of high energy photons by dust. And, that this thermal emission is made up of two or three independent components. Comparisons between the parameters obtained from the analysis of the IR SEDs and the emission in other wavelengths ranges (radio and X-rays) show that the host galaxies are key elements in the understanding of the IR emission of Seyferts. Besides, the nuclear properties seem to be adequately explained with the Unified Models of AGN, that state that the differences seen between the broad (Seyfert 1) and narrow (Seyfert 2) line objects are due to geometrical orientation effects. This revised version was published online in July 2006 with corrections to the Cover Date.     

Asteroids 1 ceres and 4 vesta: Objects of the Dawn space mission

The Dawn spacecraft of the NASA space mission to asteroids 1 Ceres and 4 Vesta was launched in September 2007. The choice of these two asteroids is deeply grounded: they are the largest and most massive objects of the main belt that are completely different in material composition, evolution history, and internal structure. Recently, the results of observations and numerical modeling have shown their amazing uniqueness: they both have experienced the complex process of thermal evolution and differentiation of their internal mineral resources, but have a completely different internal structure. Being the largest bodies, have they managed to resist the process of collisional evolution in the asteroid belt and have survived in their “primitive form.” Because of this, their study is very important from the point of view of cosmogonic problems regarding the asteroid belt and the Solar System as a whole. The present paper shortly reviews the recent progress in the study of Ceres and Vesta achieved due to observations performed on the Earth (including the polarimetric observations made by the authors) and from the Hubble Space Telescope (HST) before the long-term orbital investigations performed by the Dawn spacecraft.     

Relationship among FR-I, FR-II(Q) and FR-II(G) Radio Galaxies

Based on a sample of radio galaxies, the effective spectrum index α _RO (178 MHz to 0.54 μm), the radio and the V-band optical luminosities are investigated for FR-I, FR-II(G) and FR-II(Q).     

On the (anticipated) diversity of terrestrial planet atmospheres

On our way toward the characterization of smaller and more temperate planets, missions dedicated to the spectroscopic observation of exoplanets will teach us about the wide diversity of classes of planetary atmospheres, many of them probably having no equivalent in the Solar System. But what kind of atmospheres can we expect? To start answering this question, many theoretical studies have tried to understand and model the various processes controlling the formation and evolution of planetary atmospheres, with some success in the Solar System. Here, we shortly review these processes and we try to give an idea of the various type of atmospheres that these processes can create. As will be made clear, current atmosphere evolution models have many shortcomings yet, and need heavy calibrations. With that in mind, we will thus discuss how observations with a mission similar to EChO would help us unravel the link between a planet’s environment and its atmosphere.