Linearization Methods for Problems of Optimizing Low-Thrust Spacecraft Trajectories: Verification Procedure

Several well-studied problems for optimizing low-thrust spacecraft trajectories are solved using the modified linearization method (MLM). The results are compared with the results obtained by other authors. On this basis, conclusions are drawn on the possible use of the modified linearization method for optimizing low-thrust spacecraft trajectories.     

Asteroid (21) Lutetia as a remnant of Earth’s precursor planetesimals

Isotopic and chemical compositions of meteorites, coupled with dynamical simulations, suggest that the main belt of asteroids between Mars and Jupiter contains objects formed in situ as well as a population of interlopers. These interlopers are predicted to include the building blocks of the terrestrial planets as well as objects that formed beyond Neptune ( [Bottke et al., 2006] , [Levison et al., 2009] and [Walsh et al., 2011] ). Here we report that the main belt asteroid (21) Lutetia – encountered by the Rosetta spacecraft in July 2010 – has spectral (from 0.3 to 25 μm) and physical (albedo, density) properties quantitatively similar to the class of meteorites known as enstatite chondrites. The chemical and isotopic compositions of these chondrites indicate that they were an important component of the formation of Earth and other terrestrial planets. This meteoritic association implies that Lutetia is a member of a small population of planetesimals that formed in the terrestrial planet region and that has been scattered in the main belt by emerging protoplanets (Bottke et al. 2006) and/or by the migration of Jupiter (Walsh et al. 2011) early in its history. Lutetia, along with a few other main-belt asteroids, may contains part of the long-sought precursor material (or closely related materials) from which the terrestrial planets accreted.     

The size distribution of Jupiter's main ring from Galileo imaging and spectroscopy

Galileo's Solid State Imaging experiment (SSI) obtained 36 visible wavelength images of Jupiter's ring system during the nominal mission (Ockert-Bell et al., 1999, Icarus 138, 188-213) and another 21 during the extended mission. The Near Infrared Mapping Spectrometer (NIMS) recorded an observation of Jupiter's main ring during orbit C3 at wavelengths from 0.7 to 5.2 μm; a second observation was attempted during orbit E4. We analyze the high phase angle NIMS and SSI observations to constrain the size distribution of the main ring's micron-sized dust population. This portion of the population is best constrained at high phase angles, as the light scattering behavior of small dust grains dominates at these geometries and contributions from larger ring particles are negligible. High phase angle images of the main ring obtained by the Voyager spacecraft covered phase angles between 173.8° and 176.9° (Showalter et al., 1987, Icarus 69, 458-498). Galileo images extend this range up to 178.6°. We model the Galileo phase curve and the ring spectra from the C3 NIMS ring observation as the combination of two power law distributions. Our analysis of the main ring phase curve and the NIMS spectra suggests the size distribution of the smallest ring particles is a power law with an index of 2.0±0.3 below a size of ∼15 μm that transitions to a power law with an index of 5.0±1.5 at larger sizes. This combined power law distribution, or “broken power law” distribution, yields a better fit to the NIMS data than do the power law distributions that have previously been fit to the Voyager imaging data (Showalter et al., 1987, Icarus 69, 458-498). The broken power law distribution reconciles the results of Showalter et al. (1987, Icarus 69, 458-498) and McMuldroch et al. (2000, Icarus 146, 1-11), who also analyzed the NIMS data, and can be considered as an obvious extension of a simple power law. This more complex size distribution could indicate that ring particle production rates and/or lifetimes vary with size and may relate to the physical processes that control their evolution. The significant near arm/far arm asymmetry reported elsewhere (see Showalter et al., 1987, Icarus 69, 458-498; Ockert-Bell et al., 1999, Icarus 138, 188-213) persists in the data even after the main ring is isolated in the SSI images. However, the sense of the asymmetry seen in Galileo images differs from that seen in Voyager images. We interpret this asymmetry as a broad-scale, azimuthal brightness variation. No consistent association with the magnetic field of Jupiter has been observed. It is possible that these longitudinal variations may be similar to the random brightness fluctuations observed in Saturn's F ring by Voyager (Smith et al., 1982, Science 215, 504-537) and during the 1995 ring plane crossings (Nicholson et al., 1996, Science 272, 509-515; Bosh and Rivkin, 1996, Science 272, 518-521; Poulet et al., 2000, Icarus 144, 135-148). Stochastic events may thus play a significant role in the evolution of the jovian main ring.     

The structure of Titan’s atmosphere from Cassini radio occultations

We present results from the two radio occultations of the Cassini spacecraft by Titan in 2006, which probed mid-southern latitudes. Three of the ingress and egress soundings occurred within a narrow latitude range, 31-34°S near the surface, and the fourth at 52.8°S. Temperature-altitude profiles for all four occultation soundings are presented, and compared with the results of the Voyager 1 radio occultation (Lindal, G.F., Wood, G.E., Hotz, H.B., Sweetnam, D.N., Eshleman, V.R., Tyler, G.L. [1983]. Icarus 53, 348-363), the HASI instrument on the Huygens descent probe (Fulchignoni, M. et al. [2005]. Nature 438, 785-791), and Cassini CIRS results (Flasar, F.M. et al. [2005]. Science 308, 975-978; Achterberg, R.K., Conrath, B.J., Gierasch, P.J., Flasar, F.M., Nixon, C.A. [2008b]. Icarus 194, 263-277). Sources of error in the retrieved temperature-altitude profiles are also discussed, and a major contribution is from spacecraft velocity errors in the reconstructed ephemeris. These can be reduced by using CIRS data at 300 km to make along-track adjustments of the spacecraft timing. The occultation soundings indicate that the temperatures just above the surface at 31-34°S are about 93 K, while that at 53°S is about 1 K colder. At the tropopause, the temperatures at the lower latitudes are all about 70 K, while the 53°S profile is again 1 K colder. The temperature lapse rate in the lowest 2 km for the two ingress (dawn) profiles at 31 and 33°S lie along a dry adiabat except within ∼200 m of the surface, where a small stable inversion occurs. This could be explained by turbulent mixing with low viscosity near the surface. The egress profile near 34°S shows a more complex structure in the lowest 2 km, while the egress profile at 53°S is more stable.     

A critical analysis of three near-infrared photometric methods of estimating distances to cataclysmic variables

A critical analysis of three methods of estimating distances to cataclysmic variables (CVs) is performed. These methods, by Ak et al., Beuermann, and Knigge, all use near-infrared (JHK or K_s) magnitudes and the Barnes-Evans relation. We compare all three methods to distances measured by trigonometric parallax by Thorstensen, with Hubble Space Telescope, and with the HIPPARCOS spacecraft.We find that the method of Ak et al. works best overall for all CVs, predicting distances on the average 4% less than those measured by trigonometric parallaxes. The method of Beuermann overestimates distances by 52%. The method of Knigge underestimates distances by 26%, although this was only ever meant as a lower limit, since it assumes all light comes from the secondary star.     

Models of the collisional damping scenario for ice-giant planets and Kuiper belt formation

Chiang et al. [Chiang, E., Lithwick, Y., Murray-Clay, R., Buie, M., Grundy, W., Holman, M., 2007. In: Protostars and Planets V, pp. 895-911] have recently proposed that the observed structure of the Kuiper belt could be the result of a dynamical instability of a system of ∼5 primordial ice-giant planets in the outer Solar System. According to this scenario, before the instability occurred, these giants were growing in a highly collisionally damped environment according to the arguments in Goldreich et al. [Goldreich, P., Lithwick, Y., Sari, R., 2004. Astrophys. J. 614, 497-507; Annu. Rev. Astron. Astrophys. 42, 549-601]. Here we test this hypothesis with a series of numerical simulations using a new code designed to incorporate the dynamical effects of collisions. We find that we cannot reproduce the observed Solar System. In particular, Goldreich et al. [Goldreich, P., Lithwick, Y., Sari, R., 2004. Astrophys. J. 614, 497-507; Annu. Rev. Astron. Astrophys. 42, 549-601] and Chiang et al. [Chiang, E., Lithwick, Y., Murray-Clay, R., Buie, M., Grundy, W., Holman, M., 2007. In: Protostars and Planets V, pp. 895-911] argue that during the instability, all but two of the ice giants would be ejected from the Solar System by Jupiter and Saturn, leaving Uranus and Neptune behind. We find that ejections are actually rare and that instead the systems spread outward. This always leads to a configuration with too many planets that are too far from the Sun. Thus, we conclude that both Goldreich et al.'s scheme for the formation of Uranus and Neptune and Chiang et al.'s Kuiper belt formation scenario are not viable in their current forms.     

A method for a short-term forecast of the absorbed dose accumulation dynamics on the international space station based on radiation monitoring system data

Many papers are devoted to the prediction of radiation conditions on board of a spacecraft (Pichkhadze et al., 2004; Khamidullina et al., 2008; 2012), and a number of software systems for corresponding calculations have been developed: the US information system CREME96 (https://creme.isde.vander-bilt.edu/); European SPENVIS (http://www.spenvis.oma.be/intro.php); Russian SEREIS (Kuznetsov et al., 2001; Model’ kosmosa, 2007) and COSRAD (http://cosrad.sinp.msu.ru/manual.html; Kuznetsov et al., 2011) based on the models of the radiation environment in near-Earth space (Bashkirov et al., 1998; Nymmik, 2004; Model’ kosmosa, 2007; Kuznetsov et al., 2011). In this paper we propose a simple calculation algorithm of short-term (for a few days) forecasting of dynamics of the radiation dose on the International Space Station (ISS) in radiation environment undisturbed by solar proton events. This algorithm does not use radiation environment models and detailed ballistic calculations, while it uses data of the onboard radiation monitoring system (RMS) and empirical relations, obtained for ISS orbital motion.     

Jupiter's atmospheric temperatures: From Voyager IRIS to Cassini CIRS

Retrievals performed on Cassini Composite Infrared Spectrometer data obtained during the distant Jupiter flyby in 2000/2001 have been used to generate global temperature maps of the planet in the troposphere and stratosphere, but to higher latitudes than were shown previously by Flasar et al. [Flasar, F.M., 39 colleagues, 2004a. Nature 427, 132-135; Flasar, F.M., 44 colleagues, 2004b. Space Sci. Rev. 115, 169-297]. Similar retrievals were performed on Voyager 1 IRIS data to provide the first detailed IRIS map of the stratosphere, and high latitudes in the troposphere. Thermal winds were calculated for each data set and show strong vertical shears in the zonal winds at low latitudes, and meridional temperature gradients indicate the presence of circumpolar jets, as well. The temperatures retrieved from the two spacecraft were also compared with yearly ground-based data obtained over the intervening two decades. Tropospheric temperatures reveal gradual changes at low latitudes, with little obvious seasonal or short-term variation [Orton et al., 1994. Science 265, 625-631]. Stratospheric temperatures show much more complicated behavior over short timescales, consistent with quasi-quadrennial oscillations at low latitudes, as suggested in prior analyses of shorter intervals of ground-based data [Orton et al., 1991. Science 252, 537-542; Friedson, A.J., 1999. Icarus 137, 34-55]. A scaling analysis indicates that meridional motions, mechanically forced by wave or eddy convergence, play an important role in modulating the temperatures and winds in the upper troposphere and stratosphere on seasonal and shorter timescales. At latitudes away from the equator, the mechanical forcing can be derived simply from a temporal record of temperature and its vertical derivative. Ground-based observations with improved vertical resolution and/or long-term monitoring from spacecraft are required for this purpose, though the Voyager and Cassini data given indications that the magnitude of the forcing is very small.     

Rebuttal to the comment by Malhotra and Strom on “Constraints on the source of lunar cataclysm impactors”

?uk et al. (?uk, M. Gladman, B.J., Stewart, S.T. [2010]. Icarus 207 590-594) concluded that the the lunar cataclysm (late heavy bombardment) was recorded in lunar Imbrian era craters, and that their size distribution is different from that of main belt asteroids (which may have been the dominant pre-Imbrian impactors). This result would likely preclude the asteroid belt as the direct source of lunar cataclysm impactors. Malhotra and Strom (Malhotra, R., Strom, R.G. [2011]. Icarus) maintain that the lunar impactor population in the Imbrian era was the same as in Nectarian and pre-Nectarian periods, and this population had a size distribution identical to that of main belt asteroids. In support of this claim, they present an Imbrian size distribution made from two data sets published by Wilhelms et al. (Wilhelms, D.E., Oberbeck, V.R., Aggarwal, H.R. [1978]. Proc. Lunar Sci. Conf. 9, 3735-3762). However, these two data sets cannot be simply combined as they represent areas of different ages and therefore crater densities. Malhotra and Strom (Malhotra, R., Strom, R.G. [2011]. Icarus) differ with the main conclusion of Wilhelms et al. (Wilhelms, D.E., Oberbeck, V.R., Aggarwal, H.R. [1978]. Proc. Lunar Sci. Conf. 9, 3735-3762) that the Nectarian and Imbrian crater size distributions were different. We conclude that the available data indicate that the lunar Imbrian-era impactors had a different size distribution from the older ones, with the Imbrian impactor distribution being significantly richer in small impactors than that of older lunar impactors or current main-belt asteroids.     

Identification of spectral units on Phoebe

We apply a multivariate statistical method to the Phoebe spectra collected by the VIMS experiment onboard the Cassini spacecraft during the flyby of June 2004. The G-mode clustering method, which permits identification of the most important features in a spectrum, is used on a small subset of data, characterized by medium and high spatial resolution, to perform a raw spectral classification of the surface of Phoebe. The combination of statistics and comparative analysis of the different areas using both the VIMS and ISS data is explored in order to highlight possible correlations with the surface geology. In general, the results by Clark et al. [Clark, R.N., Brown, R.H., Jaumann, R., Cruikshank, D.P., Nelson, R.M., Buratti, B.J., McCord, T.B., Lunine, J., Hoefen, T., Curchin, J.M., Hansen, G., Hibbitts, K., Matz, K.-D., Baines, K.H., Bellucci, G., Bibring, J.-P., Capaccioni, F., Cerroni, P., Coradini, A., Formisano, V., Langevin, Y., Matson, D.L., Mennella, V., Nicholson, P.D., Sicardy, B., Sotin, C., 2005. Nature 435, 66-69] are confirmed; but we also identify new signatures not reported before, such as the aliphatic CH stretch at 3.53 μm and the ∼4.4 μm feature possibly related to cyanide compounds. On the basis of the band strengths computed for several absorption features and for the homogeneous spectral types isolated by the G-mode, a strong correlation of CO₂ and aromatic hydrocarbons with exposed water ice, where the uniform layer covering Phoebe has been removed, is established. On the other hand, an anti-correlation of cyanide compounds with CO₂ is suggested at a medium resolution scale.     

Velocity and vorticity measurements of Jupiter's Great Red Spot using automated cloud feature tracking

We have produced mosaics of the Great Red Spot (GRS) using images taken by the Galileo spacecraft in May 2000, and have measured the winds of the GRS using an automated algorithm that does not require manual cloud tracking. Our technique yields a high-density, regular grid of wind velocity vectors that is advantageous over a limited number of scattered wind vectors that result from manual cloud tracking. The high-velocity collar of the GRS is clearly seen from our velocity vector map, and highest wind velocities are measured to be around 170 m s⁻¹. The high resolution of the mosaics has also enabled us to map turbulent eddies inside the chaotic central region of the GRS, similar to those mapped by Sada et al. [Sada, P.V., Beebe, R.F., Conrath, B.J., 1996. Icarus 119, 311-335]. Using the wind velocity measurements, we computed particle trajectories around the GRS as well as maps of relative and absolute vorticities. We have discovered a narrow ring of cyclonic vorticity that surrounds the main anti-cyclonic high-velocity collar. This narrow ring appears to correspond to a ring surrounding the GRS that is bright in 5 μm [Terrile, R.J., Beebe, R.F., 1979. Science 204, 948-951]. It appears that this cyclonic ring is not a transient feature of the GRS, as we have discovered it in a re-analysis of Galileo data taken in 1996 first analyzed by Vasavada et al. [Vasavada, A.R., and 13 colleagues, 1998. Icarus 135, 265-275]. We also calculate how absolute vorticity changes as a function of latitude along a trajectory around the GRS and compare these measurements to similar ones performed by Dowling and Ingersoll [Dowling, T.E., Ingersoll, A.P., 1988. J. Atmos. Sci. 45, 1380-1396] using Voyager data. We show no dramatic evolution in the structure of the GRS since the Voyager era except for additional evidence for a counter-rotating GRS core, an increase in velocity in the main velocity collar, and an overall decrease in the length of the GRS.     

短周期激变变星周期分布的新统计

我们对周期小于周期分布空缺段的激变变星(CVs),重新进行了周期分布统计,使用了比Warner等人更多、更新的资料.统计中发现一个AM Her型CVs:GRU V1偏离了Warner等人的统计结果.我们给出了CVs 新的周期分布图和相应于此分布的随机概率.虽然结果与Warner等人的不同,但周期分布同磁场仍呈现一定的相关性,磁激变变星(MCVs)与非磁激变变星(NMCVS)同样显示出成团趋势.     

An investigation of 11 previously unstudied open star clusters

The main astrophysical properties of 11 previously unstudied open star clusters are probed with JHK Near-IR (2MASS) photometry of Cutri et al. [Cutri, R., et al., 2003. The IRSA 2MASS All-sky Point Source Catolog, NASA/IPAC Infrared Science Archive] and proper motions (NOMAD) astrometry of Zacharias et al. [Zacharias, N., Monet, D., Levine, S., Urban, S., Gaume, R., Wycoff, G., 2004. American Astro. Soc. Meeting 36, 1418]. The fundamental parameters have been derived for IC (1434, 2156); King (17, 18, 20, 23, 26); and Dias (2, 3, 4, 7, 8), for which no prior parameters are available in the literature. The clusters’ centers coordinates and angular diameters are re-determined, while ages, distances, and color excesses for these clusters are estimated here for the first time.     

Experimental and theoretical simulations of ice sublimation with implications for the chemical,isotopic, and physical evolution of icy objects

Recent ground-based and spacecraft observations of comets in the inner solar system reveal two distinct features that provide important insight into their origin and evolution. The first of these is the observation that the D/H ratio of water vapor in cometary comae is significantly higher than that in Vienna Standard Mean Ocean Water (VSMOW). The second observation is that cometary jets are bursty (i.e, roughly steady state emissions that are punctuated with short-lived outbursts of water vapor and other materials) (Hughes, 1990, Soderblom et al., 2002, Soderblom et al., 2004a, Soderblom et al., 2004b). We present an experimental and theoretical study of ice sublimation in a vacuum that reveals several heretofore unknown and fundamental characteristics about the kinetics and mechanisms of ice sublimation that may explain both of these observed phenomena. In particular, we observe quasi-periodic sublimation cascades on time scales of hours to days, the D/H ratio in the vapor issuing from the sample is in general different from that of the sample, and in many cases, quasi-periodic changes in the D/H ratio of the vapor accompany the sublimation cascades. Changes are also observed in the infrared spectrum of the sample before, during and after a cascade that are consistent with our hypothesis that vacuum sublimation of water ice is a diffusive process that works to leave behind the most strongly bound molecules. Finally, we speculate as to whether the effects observed in the lab can be extrapolated to cometary-nucleus-scale phenomena.     

A redetermination of the ice/vapor ratio of Enceladus’ plumes: Implications for sublimation and the lack of a liquid water reservoir

The discovery of plumes of H₂O vapor and ice particles erupting from the south pole of Enceladus, the tiny frigid satellite of Saturn, sparked controversy over whether these plumes are produced by boiling, or by sublimation with subsequent recondensation of the sublimated vapor [Porco, C.C., Helfenstein, P., Thomas, P.C., Ingersoll, A.P., Wisdom, J., West, R., Neukum, G., Denk, T., Wagner, R., Roatsch, T., Kieffer, S., Turtle, E., McEwen, A., Johnson, T.V., Rathbun, J., Veverka, J., Wilson, D., Perry, J., Spitale, J., Brahic, A., Burns, J.A., DelGenio, A.D., Dones, L., Murray, C.D., Squyres, S., 2006. Science 311, 1393-1401]. Porco et al.’s analysis that the masses of ice (I) and vapor (V) in the plume were comparable was taken to argue against the occurrence of sublimation and recondensation, leading to the hypothesis that the reservoir was boiling water, possibly as close as 7 m to the surface. Thus, it has been advocated that Enceladus should be a target for astrobiology exploration. Here we show, with recalculations using the original data and methodologies, as well as with new sensitivity studies, that the mass of ice in the column is significantly less than the mass of water vapor, and that by considering three additional effects, I/V is likely to be <0.2-0.1. This means that the plume is dominated by vapor that the thermodynamics permits to be easily produced by sublimation with recondensation. The low I/V ratio provides no compelling criterion for consideration of a liquid water reservoir. The uncertainties on the I/V ratio have not previously been discussed in the literature. Although the I/V ratio is sensitive to particle sizes and size distributions, the masses of ice (I) and vapor (V) are not comparable in any scenario constrained by available observations. We thus discuss the implications of sublimation from a thermodynamic point of view in a context that has not been presented previously. Constraints on I/V ratio from future spacecraft measurements of the plume, in conjunction with consideration of the total plume composition and multicomponent analysis, can help constrain source conditions for the plume.     

Nano dust impacts on spacecraft and boom antenna charging

High rate sampling detectors measuring the potential difference between the main body and boom antennas of interplanetary spacecraft have been shown to be efficient means to measure the voltage pulses induced by nano dust impacts on the spacecraft body itself (see Meyer-Vernet et al. in Sol. Phys. 256:463, 2009). However, rough estimates of the free charge liberated in post impact expanding plasma cloud indicate that the cloud’s own internal electrostatic field is too weak to account for measured pulses as the ones from the TDS instrument on the STEREO spacecraft frequently exceeding 0.1 V/m. In this paper we argue that the detected pulses are not a direct measure of the potential structure of the plasma cloud, but are rather the consequence of a transitional interruption of the photoelectron return current towards the portion of the antenna located within the expanding cloud.     

Suprathermal electron fluxes on the nightside of Mars: ASPERA-3 observations

Recently aurora-type UV emissions were discovered on the nightside of Mars [Bertaux, J.-L., Leblanc, F., Witasse, O., et al., 2005. Discovery of an aurora on Mars. Nature 439, doi:10.1038/nature03603]. It was suggested that these emissions are produced by suprathermal electrons with energies of tens of eV, rather than by the electrons with spectra peaked above 100 eV [Leblanc, F., Witasse, O., Winningham J., et al., 2006. Origin of the martian aurora observed by spectroscopy for investigation of characteristics of the atmosphere of Mars (SPICAM) onboard Mars Express. J. Geophys. Res. 111, A09313, doi:10.1029/2006JA011763]. In this paper we present observations of fluxes of suprathermal electrons (E_e≈30-100 eV) on the Martian nightside by the ASPERA-3 experiment onboard the Mars Express spacecraft. Narrow spikes of suprathermal electrons are often observed in energy-time spectrograms of electron fluxes at altitudes between 250 and 600 km. These spikes are spatially organized and form narrow strips in regions with strong upward or downward crustal magnetic field. The values of electron fluxes in such events generally could explain the observed auroral UV emissions although a question of their origin (transport from the dayside or local precipitation) remains open.     

Influence of the coorbital resonance on the rotation of the Trojan satellites of Saturn

The Cassini spacecraft collects high resolution images of the Saturnian satellites and reveals the surface of these new worlds. Tiscareno et?al. succeeded to determine the Epimetheus rotation from the Cassini Imaging Science Subsystem data, initiating studies on the rotation of Epimetheus and its companion Janus (Tiscareno et?al., Icarus 204:254?C261, 2009; Noyelles, Icarus 207:887?C902, 2010; Robutel et?al., Icarus 211:758?C769, 2011). Especially, Epimetheus is characterized by its horseshoe shape orbit and the presence of the swap has to be introduced explicitly into rotational models. During its journey in the Saturnian system, Cassini spacecraft accumulates the observational data of the other satellites and it will be possible to determine the rotational parameters of several of them. To prepare these future observations, we built rotational models of the coorbital (also called Trojan) satellites Telesto, Calypso, Helene, and Polydeuces, in addition to Janus and Epimetheus. Indeed, Telesto and Calypso orbit around the L ₄ and L ₅ Lagrange points of Saturn-Tethys while Helene and Polydeuces are coorbital of Dione. The goal of this study is to understand how the departure from the Keplerian motion induced by the perturbations of the coorbital body, influences the rotation of these satellites. To this aim, we introduce explicitly the perturbation in the rotational equations by using the formalism developed by érdi (Celest Mech 15:367?C383, 1977) to represent the coorbital motions, and so we describe the rotational motion of the coorbitals, Janus and Epimetheus included, in compact form.     

Estimating the Metallicity of Old Star Clusters in M33

1 INTRODUCTION Globular clusters are thought to be among the oldest radiant objects in the Universe. Thestudies of these systems have played a key role in the development of our understanding of theUniverse, including the fundamental question of the age of the Universe. The globular clustersof Milky Way can be used to probe the way in which our Galaxy formed. Studies of similarclusters in other galaxies can also provide us the properties of those galaxies in the early periodafter their …     

Lost siblings of the Sun: Revisiting the FGK potential candidates

The main goal of this paper is to revisit the lost siblings of the Sun candidates within 100 pc. The solar siblings should have some similar characteristics as their ages, chemical compositions and kinematics properties. Considering their chemical compositions, age and kinematics properties only three potential candidates have been found in the literature: HD28676, HD83423 and HD175740. The first two stars are mentioned by [Brown et al., 2010] and [Bobylev et al., 2011], respectively. HD175740 is, to our knowledge, the first giant to be proposed as potential candidate.