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As a result of collisions during their lifetimes, asteroids have a large variety of different shapes. It is believed that high velocity collisions or rotational spin-up of asteroids continuously replenish the Sun’s zodiacal cloud and debris disks around extrasolar planets (Jewitt (2010)). Knowledge of the spin and shape parameters of the asteroids is very important for understanding collision asteroid processes. Lately photometric observations of asteroids showed that variations in brightness are not accompanied by variations in colour index which indicate that the shape of the lightcurve is caused by varying illuminations of the asteroid surface rather than albedo variations over the surface. This conclusion became possible when photometric investigations were combined with laboratory experiments (Dunlap (1971)). In this article using the convex lightcurve inversion method we obtained the sense of rotation, pole solutions and preliminary shape of 901 Brunsia.
The identification of complex organic molecules, COMs, in inter- and circumstellar gas phase environments is steadily increasing. The formation of such COMs takes largely place on the icy dust grains, as has been shown in recent laboratory studies. Until now solid state features of smaller molecular species have been directly identified in these environments. The presented work on acetaldehyde (CH3CHO), ethanol (CH3CH2OH), and dimethyl ether (CH3OCH3) in different astronomically relevant ice environments and for temperatures in the range 15 to 160 Kelvin, provides the necessary tools to guide or interpret astronomical observations, specifically for upcoming James Webb Space Telescope observations.
Carbonaceous meteorites contain a large variety of complex organic molecules, including amino acids, nucleobases, sugar derivatives, amphiphiles, and other compounds of astrobiological interest. Photoprocessing of ices condensed on cold grains with ultraviolet (UV) photons was proposed as an efficient way to form such complex organics in astrophysical environments. This hypothesis was confirmed by laboratory experiments simulating photo-irradiation of ices containing H2O, CH3OH, CO, CO2, CH4, H2CO, NH3, HCN, etc., condensed on cold (~10–80 K) substrates. These experiments resulted in the formation of amino acids, nucleobases, sugar derivatives, amphiphilic compounds, and other organics comparable to those identified in carbonaceous meteorites. This work presents results for the formation of sugars, sugar alcohols, sugar acids, and their deoxy variants from the UV irradiation of ices containing H2O and CH3OH in relative proportions 2:1, and their comparison with meteoritic data. The formation mechanisms of these compounds and the astrobiological implications are also discussed.
We have succeeded in synthesizing organics, ‘Quenched Nitrogen-included Carbonaceous Composite (QNCC)’, via plasma chemical vapor deposition (CVD) method, whose infrared spectral properties reproduce the characteristics of the unidentified infrared (UIR) bands observed around classical novae. Past studies have shown that the UIR bands observed around novae appear somewhat differently from those observed in other astrophysical environment and are predominantly characterized by the presence of a broad 8μm feature. The remarkable similarity between the infrared properties of QNCC and the UIR bands in novae indicates that QNCC should be considered as a strong candidate of the carriers of the UIR bands in novae. Finally, we have started a space exposure experiment of QNCC aiming to explore the evolutional link between the QNCC and the insoluble organic molecule (IOM) in carbonaceous condrite and, thus, to infer the origins of organics in our solar system.
A Round Table discussion on the future of Laboratory Astrophysics and the role of IAU Commission B5 was held on the fourth day of the conference to discuss how the IAU Laboratory Astrophysics Commission (B5) can best support the astronomy community and help promote laboratory astrophysics.
The initial chemical composition of a proto-planetary nebula depends upon the degree to which 1) organic and ice components form on dust grains, 2) organic and molecular species form in the gas phase, 3) organics and ices are exchanged between the gas and solid state, and 4) the precursor and newly formed (more complex) materials survive and are modified in the developing planetary system. Infrared and radio observations of star-forming regions reveal that complex chemistry occurs on icy grains, often before stars even form. Additional processing, through the proto-planetary disk (PPD) further modifies most, but not all, of the initial materials. In fact, the modern Solar System still carries a fraction of its interstellar inheritance (Alexander et al.2017). Here we focus on three examples of small bodies in our Solar System, each containing chemical and dynamical clues to its origin and evolution: the small-cold classical Kuiper Belt object (KBO) 2014 MU69, Pluto, and Saturn’s moon, Phoebe. The New Horizons flyby of 2014 MU69 has given the first view of an unaltered body composed of material originally in the solar nebula at ~45 AU. The spectrum of MU69 reveals methanol ice (not commonly found), a possible detection of water ice, and the noteworthy absence of methane ice (Stern et al. 2019). Pluto’s internal and surface inventory of volatiles and complex organics, together with active geological processes including cryo-volcanism, indicate a surprising level of activity on a body in the outermost region of the Solar System, and the fluid that emerges from subsurface reservoirs may contain material inherited from the solar nebula (Cruikshank et al.2019a,b). Meanwhile, Saturn’s captured moon, Phoebe, carries high D/H in H2O (Clark et al. 2019) and complex organics (Cruikshank et al. 2008), both consistent with its formation in, and inheritance from, the outer region of the solar nebula. Together, these objects provide windows on the origin and evolution of our Solar System and constraints to be considered in future chemical and physical models of PPDs.
H2D+ and D2H+ are important chemical tracers of prestellar cores due to their pure rotational spectra that can be excited at the ~20 K temperature of these environments. The use of these molecules as probes of prestellar cores requires understanding the chemistry that forms and destroys these molecules. Of the eight key reactions that have been identified (Albertssonet al. 2013), five are thought to be well understood. The remaining three are the isotope exchange reactions of atomic D with H
$${ + \over 3}$$
, H2D+, and D2H+. Semi-classical results differ from the classical Langevin calculations by an order of magnitude (Moyano et al. 2004). To resolve this discrepancy, we have carried out laboratory measurements for these three reactions. Absolute cross sections were measured using a dual-source, merged fast-beams apparatus for relative collision energies between ~10 meV to ~10 eV (Hillenbrand et al. 2019). A semi-empirical model was developed incorporating high level quantum mechanical ab initio calculations for the zero-point-energy-corrected potential energy barrier in order to generate thermal rate coefficients for astrochemical models. Based on our studies, we find that these three reactions proceed too slowly at prestellar core temperatures to play a significant role in the deuteration of H
$${ + \over 3}$$
isotopologues.
A key element when modeling dust in any astrophysical environment is a self-consistent treatment of the evolution of the dust material properties (size distribution, chemical composition and structure) as they react to and adjust to the local radiation field intensity and hardness and to the gas density and dynamics. The best way to achieve this goal is to anchore as many model parameters as possible to laboratory data. In this paper, I present two examples to illustrate how outstanding questions in dust modeling have been/are being moved forward by recent advances in laboratory astrophysics and what laboratory data are still needed to further advance dust evolution models.
The desorption of volatile molecules from dust grains in cold dense clouds is crucial for the chemical inventory in the various stages of cloud collapse. In this work we investigate the desorption of N2, CO, CH4 and CO2 from surfaces of hydrogenated amorphous carbon (HAC), which, according to IR observations, is one of the main components of interstellar dust.
Implementation of a novel experimental approach using a bright source of narrowband x-ray emission has enabled the production of a photoionized argon plasma of relevance to astrophysical modelling codes such as Cloudy. We present results showing that the photoionization parameter ζ = 4πF/ne generated using the VULCAN laser was ≈ 50 erg cm s−1, higher than those obtained previously with more powerful facilities. Comparison of our argon emission-line spectra in the 4.15 - 4.25 Å range at varying initial gas pressures with predictions from the Cloudy code and a simple time-dependent code are also presented. Finally we briefly discuss how this proof-of-principle experiment may be scaled to larger facilities such as ORION to produce the closest laboratory analogue to a photoionized plasma.
In dense interstellar clouds that are shielded from high-energy radiation (e.g., UV photons or cosmic rays), H-atom addition and abstraction reactions that take place on grain surfaces play principal roles in the synthesis or decomposition of complex organic molecules (COMs). These reactions are extensively investigated with laboratory experiments by bombarding astrophysical analogue ices with a beam of low-temperature H atoms. Here we demonstrate that, although 2-4 K solid para-H2 does not represent a typical environment of the surface of interstellar grains, para-H2 matrix isolation combined with IR spectroscopy is a complementary tool to sensitively detect astrochemical hydrogenation and dehydrogenation processes.
Saturn’s moon Titan was explored by the Cassini mission for nearly 13 years. Important discoveries made during the Cassini mission include the observations of stratospheric clouds in Titan’s cold polar regions in which spectral features or organic molecules were detected in the infrared (<100 μm). In particular, benzene (C6H6) ice spectral signatures were recently detected at unexpectedly high altitudes over the South Pole. The combined experimental, modeling and observational effort presented here has been devised and executed in order to interpret these high altitude benzene observations. Our multi-disciplinary approach aims to understand and characterize the microphysics of benzene clouds in Titan’s South Pole.
While gas-phase reactions and surface reactions on bare carbonaceous or siliceous dust grains contribute to cosmic chemistry, the energetic processing of cosmic ices via photochemistry and radiation chemistry is thought to be the dominant mechanism for the cosmic synthesis of prebiotic molecules. Because most previous laboratory astrochemical studies have used light sources that produce >10 eV photons and are, therefore, capable of ionizing cosmic ice analogs, discerning the role of photochemistry vs. radiation chemistry in astrochemistry is challenging. By using a source whose photon energy does not exceed 8 eV, we have studied ammonia and methanol cosmic ice reactions attributable solely to photochemistry. We compare these results to those obtained in the same ultrahigh vacuum chamber with 1 keV electrons which instead initiate radiation chemistry in cosmic ice analogs.
HD 66051 is an eclipsing and spectroscopic double-lined binary (SB2), hosting two chemically peculiar stars: a highly peculiar B star as primary and an Am star as secondary. The investigation of the new high-resolution UVES spectrum of HD 66051 allowed us to decide on the chemical peculiarity type of both components with more reliability. An analysis of TESS photometric time series data will further specify the physical parameters of the stars and the orbital parameters of the system.
By virtue of the physical, chemical and dynamical characteristics of asteroids, researchers gain insight into the formation and evolution of our Solar system. Since these objects do not undergo any changes, or the changes during the Solar system evolution are insignificant, we are certain they carry important information regarding the formation of our planetary system and its evolution. Knowing the spectral class of an asteroid is crucial for determining its chemical properties. In our work the spectral classification was done on several asteroids by comparing their spectra with laboratory spectra. We determined spectral types of the asteroids by the overall shapes of the spectra between 450 nm and 700 nm. Increasing the number of asteroids with known rotation period, shapes and spectra enriches the asteroid database of physical and dynamical characteristics of asteroid population.
We present results of full general relativistic (GR), three-dimensional (3D) core-collapse simulation of a massive star with multi-energy neutrino transport. Using a 70Mȯ zero-metallicity star, we show that the black-hole (BH) formation occurs at ∼ 300 ms after bounce. At a few ∼ 10 ms before the BH formation, we find that the stalled bounce shock is revived by neutrino heating from the forming hot proto-neutron star (PNS), which is aided by vigorous convection behind the shock. Our numerical results present the first evidence to validate the BH formation by the so-called fallback scenario. Furthermore we present results from a rapidly rotating core-collapse model of a 27Mȯ star that is trending towards an explosion. We point out that the correlated neutrino and gravitational-wave signatures, if detected, could provide a smoking-gun evidence of rapid rotation of the newly-born PNS.
We propose a role for CO ice mantles in ion recombination reactions, and demonstrate how the subsequent fall in the degree of gas phase ionization decreases the time required for cloud collapse under gravity by a factor of 5-6. Experimental results demonstrate that CO films prepared at cryo-temperatures spontaneously harbour electric fields immediately upon growth. Using what is known from observations about prestellar cloud conditions in the ISM, we explain how this phenomenon can lead to an acceleration in ion recombination reaction rates. The result is a pathway for cloud collapse to occur before cloud disruption by supernova remnants.
Understanding the physical structure of the planet formation environment, the protoplanetary disk, is essential for the interpretation of high resolution observations of the dust and future observations of the magnetic field structure. Observations of multiple transitions of molecular species offers a unique view of the underlying physical structure through excitation analyses. Here we describe a new method to extract high-resolution spectra from low-resolution observations, then provide two case studies of how molecular excitation analyses were used to constrain the physical structure in TW Hya, the closest protoplanetary disk to Earth.
The role of H2 in forming interstellar complex organics is still not clear due to the high activation energies required for “non-energetic” association reactions. In this work, we investigated the potential contribution of H2 to the hydrogenated species (HnNCO) formation on dust grains when the “energetic” processing is involved. The goal is to test whether an additional hydrogenation pathway is possible upon UV irradiation of a CO:H2 ice mixture. It is proposed that the electronically excited carbon monoxide (CO*) induced by UV-photons can react with a ground-state H2 to form HCO, ultimately enhancing the production of COMs in ice mantle.
The outflows of asymptotic giant branch (AGB) stars are important astrochemical laboratories, rich in molecular material and host to various chemical processes, including dust formation. Since the different chemistries are relatively easily probed, AGB outflows are ideal testbeds within the wider astrochemical community. Recent observations are pushing the limits of both our current chemical models and radiative transfer routines. Current chemical models are restricted by the completeness of their chemical networks and the accuracy of the reaction rates. The molecular abundances retrieved by radiative transfer routines are strongly dependent on collisional rates, which are often not measured or calculated for molecules of interest. To further our understanding of the chemistry within the outflow, collaboration with the laboratory astrophysics community is essential. This collaboration is mutually beneficial, as it in turn provides new science questions for laboratory experiments and computations.