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NASA NTRS2003

X-ray Haloes and Scattering by Interstellar Grains

The presence of dust in the general interstellar medium is inferred f r o m the general extinction of starlight, the diffuse infrared emission, and the elemental abundance constraints. X-ray haloes around X-ray sources, produced by small angle scattering from intervening interstellar dust particles provide a new probe into the nature of interstellar dust. In this talk I will review the physics of X-ray scattering by dust particles, and present an analysis of dust properties around select X-ray sources.

Dwek, Eliahu↗

NASA NTRS2004

Interstellar Dust Models

A viable interstellar dust model - characterized by the composition, morphology, and size distribution of the dust grains and by the abundance of the different elements locked up in the dust - should fit all observational constraints arising primarily from the interactions of the dust with incident radiation or the ambient gas. As a minimum, these should include the average interstellar extinction, the infrared emission from the diffuse interstellar medium (ISM), and the observed interstellar abundances of the various refractory elements. The last constraint has been largely ignored, resulting in dust models that require more elements to be in the dust phase than available in the ISM. In this talk I will describe the most recent advances towards the construction of a comprehensive dust model made by Zubko, Dwek, and Arendt, who, for the first time, included the interstellar abundances as explicit constraints in the construction of interstellar dust models. The results showed the existence of many distinct models that satisfy the basic set of observational constraints, including bare spherical silicate and graphite particles, PAHs, as well as spherical composite particles containing silicate, organic refractories, water ice, and voids. Recently, a new interstellar dust constituent has emerged, consisting of metallic needles. These needles constitute a very small fraction of the interstellar dust abundance, and their existence is primarily manifested in the 4 to 8 micron wavelength region, where they dominate the interstellar extinction. Preliminary studies show that these models may be distinguished by their X-ray halos, which are produced primarily by small angle scattering off large dust particles along the line of sight to bright X-ray sources, and probe dust properties largely inaccessible at other wavelengths.

Dwek, Eli↗

NASA NTRS2012

A Peculiar Class of Debris Disks from Herschel/DUNES: A Steep Fall Off in the Far Infrared

Context. The existence of debris disks around old main sequence stars is usually explained by continuous replenishment of small dust grains through collisions from a reservoir of larger objects. Aims. We present photometric data of debris disks around HIP 103389 (HD199260), HIP 100350 (HN Peg, HD206860), and HIP 114948 (HD 219482), obtained in the context of our Herschel Open TIme Key Program DUNES (DUst around NEarby Stars). Methods. We used Herschel/PACS to detect the thermal emission of the three debris disks with a 30 sigma sensitivity of a few mJy at l00 micron and 160 micron. In addition, we obtained Herschel/PACS photometric data at 70 micron for HIP 103389. These observations are complemented by a large variety of optical to far-infrared photometric data. Two different approaches are applied to reduce the Herschel data to investigate the impact of data reduction on the photometry. We fit analytical models to the available spectral energy distribution (SED) data using the fitting method of simulated therma1 annealing as well as a classical grid search method. Results. The SEDs of the three disks potentially exhibit an unusually steep decrease at wavelengths >= 70 micron. We investigate the significance of the peculiar shape of these SEDs and the impact on models of the disks provided it is real. Using grain compositions that have been applied successfully for modeling of many other debris disks, our modeling reveals that such a steep decrease of the SEDs in the long wavelength regime is inconsistent with a power-law exponent of the grain size distribution -3.5 expected from a standard equilibrium collisional cascade. In contrast, a steep grain size distribution or, alternatively an upper grain size in the range of few tens of micrometers are implied. This suggests that a very distinct range of grain sizes would dominate the thermal. emission of such disks. However, we demonstrate that the understanding of the data of faint sources obtained with Herschel is still incomplete and that the significance of our results depends on the version of the data reduction pipeline used. Conclusions. A new mechanism to produce the dust in the presented debris disks, deviations from the conditions required for a standard equilibrium collisional cascade (grain size exponent of -3.5), and/or significantly different dust properties would be necessary to explain the potentially steep SED shape of the three debris disks presented.

Ertel, S.↗

NASA NTRS2012

Debris Disk Structure and Morphology as Revealed by Aggressive STIS Multi-Roll Coronagraphy: A New Look at Some Old Friends

We present new imaging results from a well-selected sample of II circumstellar debris disks, all with HST pedigree, using STIS visible-light 6-roll PSF-template subtracted coronagraphy (PSFTSC). These new observations, pushing HST to its highest levels of coronagraphic performance, simultaneously probe both the interior regions of these debris systems, with inner working distances < app 8 AU for half the stars in this sample (corresponding to the giant planet and Kuiper belt regions within our own solar system), and the exterior regions far beyond. These new images enable direct inter-comparison of the architectures of these exoplanetary debris systems in the context of our own Solar System: These observations also permit us, for the first time, to characterize material in these regions at high spatial resolution and identify disk sub-structures that are signposts of planet formation and evolution; in particular, asymmetries and non-uniform debris structures that signal the presence of co-orbiting perturbing planets, and dynamical interactions (e.g., resulting in posited small grain stripping and disk "pollution") with the ISM. We focus here on recently acquired and reduced images of he circumstellar debris systems about: AU Mic (edge-on, and @ 10 pc the closest star in our sample), HD 61005, HD 32297 and HD 15115 (all with morphologies strongly suggestive of ISM wind interactions), HD 181327 & HDI07146 (close to face-on with respectively narrow and broad debris rings), and MP Mus (a "mature" proto-planetary disk hosted by a cTTS). All of our objects were previously observed in the near-IR with inferior spatial resolution and imaging efficacy, but with NICMOS r = 0.3" inner working angle (IWA) comparable to STIS multi-roll coronagraphy. The combination of new optical and existing near-IR imaging can strongly constrain the dust properties, thus enabling an assessment of grain processing and planetesimal populations. These results will directly inform upon the posited planet formation mechanisms that occur after the approximately 10 My epoch of gas depletion, a time in our solar system when giant planets were migrating and terrestrial planets were forming, and directly test theoretical models of these processes. These observations lmiquely probe both into the interior regions of these systems and are sensitive to and spatially resolve low surface-brightness (SB) material at large stellocentric distances with spatial resolution comparable to ACS and with augmenting NICMOS near-IR disk photometry in hand.

Grady, Carol A↗

NASA NTRS2018

Subaru/HiCIAO HK(sub S) Imaging of LKHa 330: Multi-Band Detection of the Gap and Spiral-Like Structures

We present H- and K s-bands observations of the LkHα 330 disk with a multi-band detection of the large gap and spiral-like structures. The morphology of the outer disk (r ~ 0."3) at PA = 0°–45° and PA° = 180–290° is likely density wave-induced spirals, and comparison between our observational results and simulations suggests a planet formation. We have also investigated the azimuthal profiles at the ring and the outer-disk regions as well as radial profiles in the directions of the spiral-like structures and semimajor axis. Azimuthal analysis shows a large variety in wavelength and implies that the disk has non-axisymmetric dust distributions. The radial profiles in the major-axis direction (PA = 271°) suggest that the outer region (r ≥ 0."25) may be influenced by shadows of the inner region of the disk. The spiral-like directions (PA = 10° and 230°) show different radial profiles, which suggests that the surfaces of the spiral-like structures are highly flared and/or have different dust properties. Finally, a color map of the disk shows a lack of an outer eastern region in the H-band disk, which may hint at the presence of an inner object that casts a directional shadow onto the disk.

H- and Ks-bands observations↗

NASA NTRS2021

Far-infrared Imager and Polarimeter for the Origins Space Telescope

The far-infrared imager and polarimeter (FIP) for the Origins Space Telescope (Origins) is a basic far-infrared imager and polarimeter. The camera will deliver continuum images and polarization measurements at 50 and 250μm. Currently available detector technologies provide sufficient sensitivity for background limited observations from space, at least on a single pixel basis. FIP incorporates large next-generation superconducting detector arrays and our technology development plan will push the pixel numbers for the arrays to the required size of 8000. Two superconducting detector technologies are currently candidates for the instrument: transition edge sensors or microwave kinetic inductance devices. Using these detectors and taking advantage of the cryogenic telescope that is provided by Origins, FIP will achieve mapping speeds of up to eight orders of magnitude faster than what has been achieved by existing observatories. The science drivers for FIP include observations of solar system objects, dust properties, and magnetic field studies of the nearby interstellar medium, and large scale galaxy surveys to better constrain the star formation history of the universe to address one of the main themes of Origins: “How does the Universe work?” In addition to the science, the FIP instrument plays a critical functional role in aligning the mirrors during on orbit observatory commissioning.

Astronomy↗

NASA NTRS2019

Magnification, dust, and time-delay constraints from the first resolved strongly lensed Type Ia supernova iPTF16geu

We report lensing magnifications, extinction, and time-delay estimates for the first resolved, multiply imaged Type Ia supernova iPTF16geu, at z = 0.409, using Hubble Space Telescope (HST) observations in combination with supporting ground-based data. Multiband photometry of the resolved images provides unique information about the differential dimming due to dust in the lensing galaxy. Using HST and Keck AO reference images taken after the SN faded, we obtain a total lensing magnification for iPTF16geu of μ = 67.8(+2.6−2.9), accounting for extinction in the host and lensing galaxy. As expected from the symmetry of the system, we measure very short time-delays for the three fainter images with respect to the brightest one: −0.23 ± 0.99, −1.43 ± 0.74, and 1.36 ± 1.07 d. Interestingly, we find large differences between the magnifications of the four supernova images, even after accounting for uncertainties in the extinction corrections: ∆m(1) = −3.88(+0.07−0.06), ∆m(2) = −2.99(+0.09−0.08), ∆m(3) = −2.19(+0.14−0.15),and ∆m(4) = −2.40(+0.14−0.12) mag, discrepant with model predictions suggesting similar image brightnesses. A possible explanation for the large differences is gravitational lensing by substructures, micro- or millilensing, in addition to the large-scale lens causing the image separations. We find that the inferred magnification is insensitive to the assumptions about the dust properties in the host and lens galaxy.

S Dhawan↗

NASA NTRSDate not supplied

Parallel plate capacitor TiN KID array development for the Balloon Experiment for Galactic Infrared Science

The Balloon Experiment for Galactic Infrared Science (BEGINS) will map dust spectral energy distributions (SEDs) between 25 and 250 microns near high-mass star regions, characterizing the radiation fields and dust properties of a variety of stellar environments. To accomplish these goals, BEGINS will be outfitted with roughly 1,800 titanium nitride (TiN), superconducting kinetic inductance detectors (KIDs). A parallel plate capacitor KID design is used to achieve high pixel density arrays. A cryogenic, silicon-based, metal-mesh linear variable filter will define detector band passes across the KID array. Optical coupling to the filters and telescope will be accomplished using silicon microlenses. Here we present laboratory characterization of prototype BEGINS detector arrays, describe future array development plans, and describe the testbed used to characterize the arrays.

Nicholas F. Cothard↗

NASA NTRS2021

A Layered Debris Disk around M Star TWA 7 in Scattered Light

We have obtained Hubble Space Telescope (HST) coronagraphic observations of the circumstellar disk around M star TWA 7 using the Space Telescope Imaging Spectrograph (STIS) instrument in visible light. Together with archival observations, including HST/NICMOS using the F160W filter and Very Large Telescope/SPHERE at the H-band in polarized light, we investigate the system in scattered light. By studying this nearly face-on system using geometric disk models and Henyey–Greenstein phase functions, we report a new discovery of a tertiary ring and a clump. We identify a layered architecture: three rings, a spiral, and an ≈150 au 2 elliptical clump. The most extended ring peaks at 28 au, and the other components are on its outskirts. Our point-source detection-limit calculations demonstrate the necessity of disk modeling in imaging fainter planets. Morphologically, we witness a clockwise spiral motion, and the motion pattern is consistent with both solid body motion and local Keplerian motion; we also observe underdensity regions for the secondary ring that might result from mean-motion resonance or moving shadows: both call for re-observations to determine their nature. Comparing multi-instrument observations, we obtain blue STIS-NICMOS color, a STIS-SPHERE radial distribution peak difference for the tertiary ring, and a high SPHERE-NICMOS polarization fraction; these aspects indicate that TWA 7 could retain small dust particles. By viewing the debris disk around M star TWA 7 at a nearly face-on vantage point, our study allows for the understanding of such disks in scattered light in both system architecture and dust property.

Debris disks↗

NASA NTRS1982

The Halley dust model

The properties of dust ejecta from Comet Halley are studied on the basis of (a) evidence from the comet's past apparitions and (b) analogy with recent, physically similar comets. Specifically discussed are the light curve and spectrum, discrete phenomena in the head, the physical properties of the nucleus (size, albedo, rotation, surface temperature, and morphology), and an interaction between the nucleus and dust atmosphere. Also reviewed are constraints on the size and mass distributions of dust particles, information on submicron-size and submillimeter-size grains from the comet's dust tail and antitail, and the apparent existence of more than one particle type. Similarities between the jet patterns of Halley and the parent comet of the Perseid meteor stream are depicted, and effects of the surface heterogeneity (discrete active regions) on the dust flow are assessed. Current dust models for Halley are summarized and the existence of short-term variations in the dust content in the comet's atmosphere is suggested.

Sekanina, Z.↗

NASA NTRSDate not supplied

Thermo-Optical Properties of Lunar Dust Simulants

Lunar dust coverage can significantly impact the thermo-optical properties of external surfaces for spacecraft and systems operating in the Lunar orbit or on the Lunar surface. This impacts the thermal control of these vehicles. Testing must be done to determine how much surface optics are affected by varying levels of lunar dust coverage. Optics and Particle Size Distributions (PSDs) of the dust simulant used in these tests are critical to the results. Many lunar dust simulants are available for testing, but their thermooptical properties are not well characterized. To resolve this unknown, 13 different lunar dust simulants’ IR emissivity and solar absorptivity were measured and are presented with their PSDs here.

lunar dust↗

NASA NTRSDate not supplied

Thermo-Optical Properties of Lunar Dust Simulants

lunar dust↗

NASA NTRS1973

Optical Properties of atmospheric dust from twilight observations

Three methods of approximation are described and used to separate the primary twilight brightness from the observed brightness. Photoelectric observations obtained are combined with observations from a balloon and from the observatory to derive the atmospheric scattering phase functions of 0.37 micron and 0.58 micron as a function of height. Comparison of these data with data for a Rayleigh atmosphere provide information on the optical properties of dust in the upper atmosphere.

Divari, N. B.↗

NASA NTRS1986

Observations and theories of interstellar dust

The observational properties of dust are summarized based on: the extinction over a factor of 100 in wavelength (0.1 to 10 microns); polarization, both linear and circular; narrow emission and absorption features in the spectrom; and reflection nebulae.

Mathis, J. S.↗

NASA NTRS2024

Chemical and Physical Properties of Cometary Dust

Cometary dust particles are best preserved remnants of the matter present at the onset of the formation of the Solar System. In Space missions, telescopic observations and laboratory analyses advanced the knowledge on the properties of cometary dust. the only samples certified with a cometary origin were returned by the Stardust space mission from comet 81P/Wild2. The “chondritic porous” (here called “chondritic anhydrous”) interplanetary dust particles (CA-IDPs) and micrometeorites (CP-MMs), and the ultracarbonaceous Antarctic MMs (UCAMMs) also show strong evidence for a cometary origin. The elemental composition of cometary dust is generally consistent with the chondritic (CI) composition, with the notable exception of elevated contents in carbon and nitrogen compared with CI. The organic matter of cometary dust is mixed with minor amounts of crystalline (at least 25% of the minerals) and amorphous mineral phases. The most abundant crystalline minerals are ferromagnesian silicates (olivine and low-Ca pyroxenes), but High-Ca pyroxenes, refractory minerals and Low Ni Fe sulfides are also present. The crystalline olivine and low-Ca pyroxene compositions can vary from their Mg-rich end-member (forsterite and enstatite) to relatively Fe-rich compositions. Refractory minerals as well as secondary minerals likeLIME (low-iron, Mn-enriched) olivines, unusual Fe sulfides or mineral aggregates of specific compositions like Kosmochloric high-Ca pyroxene and FeO-rich olivine - KOOL grains) are also found. The presence of carbonates in cometary dust is still debated, but a phyllosilicate-like phase was observed in a UCAMM. The abundance of pyroxene to olivine (in numbers) is larger than in primitive meteorites (e.g. the Px/Ol ratio is usually larger than 1). GEMS phases (glass with embedded metals and sulfides) are abundant in cometary dust, although not systematically found. Some of the organic matter present in cometary dust particle resembles the insoluble organic matter (IOM) present in primitive meteorites, but amorphous carbon and exotic (e.g. N-rich) organic phases are also present. The hydrogen isotopic composition of cometary dust particles (in the organic matter) is usually rich in deuterium, tracing a formation at very low temperatures, either in the protosolar cloud or in the outer regions of the protoplanetary disk. The presolar dust concentration in cometary dust can reach about 1%, which is the most elevated value observed in extraterrestrial samples. The size distribution of cometary dust in comet trails is well represented by a power-law distribution (differential size distribution) with a mean power index N typically ranging from -3 to -4. Polarimetric and light scattering studies of cometary dust suggest mixtures of porous agglomerates of sub-micrometer minerals with organic matter, which is compatible with the in situ analyses of 67P/Churyumov-Gerasimenko by MIDAS (Rosetta) and with the studies of it Stardust samples, CA-IDPs, CP-MMs and UCAMMs. Cometary dust particles have low tensile strength, and low density.

C. Engrand↗

NASA NTRS2011

Measuring the Optical Properties of Astrophysical Dust Analogues: Instrumentation and Methods

Dust is found throughout the universe and plays an important role for a wide range of astrophysical phenomena. In recent years, new infrared facilities have provided powerful new data for understanding these phenomena. However, interpretation of these data is often complicated by a lack of complementary information about the optical properties of astronomically relevant materials. The Optical Properties of Astronomical Silicates with Infrared Techniques (OPASI-T) program at NASA's Goddard Space Flight Center is designed to provide new high-quality laboratory data from which we can derive the optical properties of astrophysical dust analogues. This program makes use of multiple instruments, including new equipment designed and built specifically for this purpose. The suite of instruments allows us to derive optical properties over a wide wavelength range, from the near-infrared through the millimeter, also providing the capability for exploring how these properties depend upon the temperature of the sample. In this paper, we discuss the overall structure of the research program, describe the new instruments that have been developed to meet the science goals, and demonstrate the efficacy of these tools.

Rinehart, S. A.↗

NASA NTRS2017

Chemical, Mineralogical, and Physical Properties of Martian Dust and Soil

Global and regional dust storms on Mars have been observed from Earth-based telescopes, Mars orbiters, and surface rovers and landers. Dust storms can be global and regional. Dust is material that is suspended into the atmosphere by winds and has a particle size of 1-3 micrometer. Planetary scientist refer to loose unconsolidated materials at the surface as "soil." The term ''soil'' is used here to denote any loose, unconsolidated material that can be distinguished from rocks, bedrock, or strongly cohesive sediments. No implication for the presence or absence of organic materials or living matter is intended. Soil contains local and regional materials mixed with the globally distributed dust by aeolian processes. Loose, unconsolidated surface materials (dust and soil) may pose challenges for human exploration on Mars. Dust will no doubt adhere to spacesuits, vehicles, habitats, and other surface systems. What will be the impacts on human activity? The objective of this paper is to review the chemical, mineralogical, and physical properties of the martian dust and soil.

Ming, D. W.↗

NASA NTRS1988

The spectral properties of collected interplanetary dust particles

The observed spectral and mineralogical properties of interplanetary dust particles (IDP) allows the conclusion that: (1) the majority of IDP infrared spectra are dominated by olivine, pyroxene, or layer lattice silicate minerals, (2) to the first order the emission spectra of comets Halley and Kohoutek can be matched by mixtures of these IDP infrared types, implying that comets contain mixtures of these different crystalline silicates and may vary from comet to comet and perhaps even within a single comet, (3) do not expect to observe a single 20 micron feature in cometary spectra, (4) carbonaceous materials dominate the visible spectra properties of the IDPs even though the mass in these particles consists primarily of silicates, and (5) the particle characteristics summarized need to be properly accounted for in future cometary emission models.

Sandford, S. A.↗