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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

The color–magnitude distribution of small Jupiter Trojans

We present an analysis of survey observations targeting the leading L4 Jupiter Trojan cloud near opposition using the wide-field Suprime-Cam CCD camera on the 8.2 m Subaru Telescope. The survey covered about 38 deg{sup 2} of sky and imaged 147 fields spread across a wide region of the L4 cloud. Each field was imaged in both the g' and the i' band, allowing for the measurement of g – i color. We detected 557 Trojans in the observed fields, ranging in absolute magnitude from H = 10.0 to H = 20.3. We fit the total magnitude distribution to a broken power law and show that the power-law slope rolls over from 0.45 ± 0.05 to 0.36{sub -0.09}{sup +0.05} at a break magnitude of H{sub b}=14.93{sub -0.88}{sup +0.73}. Combining the best-fit magnitude distribution of faint objects from our survey with an analysis of the magnitude distribution of bright objects listed in the Minor Planet Center catalog, we obtain the absolute magnitude distribution of Trojans over the entire range from H = 7.2 to H = 16.4. We show that the g – i color of Trojans decreases with increasing magnitude. In the context of the less-red and red color populations, as classified in Wong et al. using photometric and spectroscopic data, we demonstrate that the observed trend in color for the faint Trojans is consistent with the expected trend derived from extrapolation of the best-fit color population magnitude distributions for bright cataloged Trojans. This indicates a steady increase in the relative number of less-red objects with decreasing size. Finally, we interpret our results using collisional modeling and propose several hypotheses for the color evolution of the Jupiter Trojan population.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

EXOPLANET ALBEDO SPECTRA AND COLORS AS A FUNCTION OF PLANET PHASE, SEPARATION, AND METALLICITY

First generation space-based optical coronagraphic telescopes will obtain images of cool gas- and ice-giant exoplanets around nearby stars. Exoplanets lying at planet-star separations larger than about 1 AU-where an exoplanet can be resolved from its parent star-have spectra that are dominated by reflected light to beyond 1 {mu}m and punctuated by molecular absorption features. Here, we consider how exoplanet albedo spectra and colors vary as a function of planet-star separation, metallicity, mass, and observed phase for Jupiter and Neptune analogs from 0.35 to 1 {mu}m. We model Jupiter analogs with 1x and 3x the solar abundance of heavy elements, and Neptune analogs with 10x and 30x the solar abundance of heavy elements. Our model planets orbit a solar analog parent star at separations of 0.8 AU, 2 AU, 5 AU, and 10 AU. We use a radiative-convective model to compute temperature-pressure profiles. The giant exoplanets are found to be cloud-free at 0.8 AU, possess H{sub 2}O clouds at 2 AU, and have both NH{sub 3} and H{sub 2}O clouds at 5 AU and 10 AU. For each model planet we compute moderate resolution (R = {lambda}/{Delta}{lambda} {approx} 800) albedo spectra as a function of phase. We also consider low-resolution spectra and colors that are more consistent with the capabilities of early direct imaging capabilities. As expected, the presence and vertical structure of clouds strongly influence the albedo spectra since cloud particles not only affect optical depth but also have highly directional scattering properties. Observations at different phases also probe different volumes of atmosphere as the source-observer geometry changes. Because the images of the planets themselves will be unresolved, their phase will not necessarily be immediately obvious, and multiple observations will be needed to discriminate between the effects of planet-star separation, metallicity, and phase on the observed albedo spectra. We consider the range of these combined effects on spectra and colors. For example, we find that the spectral influence of clouds depends more on planet-star separation and hence atmospheric temperature than metallicity, and it is easier to discriminate between cloudy 1x and 3x Jupiters than between 10x and 30x Neptunes. In addition to alkalis and methane, our Jupiter models show H{sub 2}O absorption features near 0.94 {mu}m. While solar system giant planets are well separated by their broadband colors, we find that arbitrary giant exoplanets can have a large range of possible colors and that color alone cannot be relied upon to characterize planet types. We also predict that giant exoplanets receiving greater insolation than Jupiter will exhibit higher equator-to-pole temperature gradients than are found on Jupiter and thus may exhibit differing atmospheric dynamics. These results are useful for future interpretation of direct imaging exoplanet observations as well as for deriving requirements and designing filters for optical direct imaging instrumentation.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2011

LIFTING THE DUSTY VEIL WITH NEAR- AND MID-INFRARED PHOTOMETRY. I. DESCRIPTION AND APPLICATIONS OF THE RAYLEIGH-JEANS COLOR EXCESS METHOD

The Milky Way (MW) remains a primary laboratory for understanding the structure and evolution of spiral galaxies, but typically we are denied clear views of MW stellar populations at low Galactic latitudes because of extinction by interstellar dust. However, the combination of Two Micron All-Sky Survey (2MASS) near-infrared (NIR) and Spitzer-IRAC mid-infrared (MIR) photometry enables a powerful method for determining the line-of-sight reddening to any star: the sampled wavelengths lie in the Rayleigh-Jeans part of the spectral energy distribution of most stars, where, to first order, all stars have essentially the same intrinsic color. Thus, changes in stellar NIR-MIR colors due to interstellar reddening are readily apparent, and (under an assumed extinction law) the observed colors and magnitudes of stars can be easily and accurately restored to their intrinsic values, greatly increasing their usefulness for Galactic structure studies. In this paper, we explore this 'Rayleigh-Jeans Color Excess' (RJCE) method and demonstrate that use of even a simple variant of the RJCE method based on a single reference color, (H -[4.5{mu}]), can rather accurately remove dust effects from previously uninterpretable 2MASS color-magnitude diagrams of stars in fields along the heavily reddened Galactic midplane, with results far superior to those derived from application of other dereddening methods. We also show that 'total' Galactic midplane extinction looks rather different from that predicted using 100{mu} emission maps from the IRAS/ISSA and COBE/DIRBE instruments as presented by Schlegel et al. Instead, the Galactic midplane extinction strongly resembles the distribution of {sup 13}CO (J = 1{yields}0) emission. Future papers will focus on refining the RJCE method and applying the technique to understand better not only dust and its distribution but also the distribution of stars intermixed with the dust in the low-latitude Galaxy.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2021

Museomics Dissects the Genetic Basis for Adaptive Seasonal Coloration in the Least Weasel

Abstract Dissecting the link between genetic variation and adaptive phenotypes provides outstanding opportunities to understand fundamental evolutionary processes. Here, we use a museomics approach to investigate the genetic basis and evolution of winter coat coloration morphs in least weasels (Mustela nivalis), a repeated adaptation for camouflage in mammals with seasonal pelage color moults across regions with varying winter snow. Whole-genome sequence data were obtained from biological collections and mapped onto a newly assembled reference genome for the species. Sampling represented two replicate transition zones between nivalis and vulgaris coloration morphs in Europe, which typically develop white or brown winter coats, respectively. Population analyses showed that the morph distribution across transition zones is not a by-product of historical structure. Association scans linked a 200-kb genomic region to coloration morph, which was validated by genotyping museum specimens from intermorph experimental crosses. Genotyping the wild populations narrowed down the association to pigmentation gene MC1R and pinpointed a candidate amino acid change cosegregating with coloration morph. This polymorphism replaces an ancestral leucine residue by lysine at the start of the first extracellular loop of the protein in the vulgaris morph. A selective sweep signature overlapped the association region in vulgaris, suggesting that past adaptation favored winter-brown morphs and can anchor future adaptive responses to decreasing winter snow. Using biological collections as valuable resources to study natural adaptations, our study showed a new evolutionary route generating winter color variation in mammals and that seasonal camouflage can be modulated by changes at single key genes.

Miranda, Inês↗
DOE OSTI2018

Colors of Centaurs observed by the Subaru/Hyper Suprime-Cam and implications for their origin

Abstract Centaurs have orbits between Jupiter and Neptune and are thought to originate from the trans-Neptunian region. Observations of surface properties of Centaurs and comparison with those of trans-Neptunian objects (TNOs) would provide constraints on their origin and evolution. We analyzed imaging data of nine known Centaurs observed by the Hyper Suprime-Cam (HSC) installed on the Subaru Telescope with the g- and i-band filters. Using the data available in the public HSC data archive, as well as those obtained by the HSC Subaru Strategic Program (HSC-SSP) by the end of 2017 June, we obtained the g − i colors of the nine Centaurs. We compared them with those of known TNOs in the HSC-SSP data obtained by T. Terai et al. (2018, PASJ, 70, S40). We found that the color distribution of the nine Centaurs is similar to that of those TNOs with high orbital inclinations, but distinct from those TNOs with low orbital inclinations. We also examined correlations between the colors of these Centaurs and their orbital elements and absolute magnitude. The Centaurs’ colors show a moderate positive correlation with semi-major axis, while no significant correlations between the color and other orbital elements or absolute magnitude were found for these Centaurs. On the other hand, recent studies on Centaurs with larger samples show interesting correlations between their color and absolute magnitude or orbital inclination. We discuss how our data fit in these previous studies, and also discuss implications of these results for their origin and evolution.

Sakugawa, Haruka↗
DOE OSTI2019

A Synchronization-Avoiding Distance-1 Grundy Coloring Algorithm for Power-Law Graphs

In this paper, we propose a distributed, unordered, label-correcting distance-1 Grundy (vertex) coloring algorithm, namely, Distributed Control (DC) coloring algorithm. Our algorithm eliminates the need for vertex-centric barriers and global synchronization for color refinement, relying only on atomic operations and local termination detection to update vertex color. DC proceeds optimistically, correcting the colors asynchronously as the algorithm progresses and depends on local ordering of tasks to minimize the execution of sub-optimal work. We implement our DC coloring algorithm and the well-known Jones-Plassmann algorithm and compare their performance with 4 different types of standard RMAT graphs and real-world graphs. We show that the elimination of waiting time of global and vertex-centric barriers and investing this time for local ordering leads to improved scaling for graphs with prominent power-law characteristics and densely interconnected local subgraphs.

Firoz, Jesun S.↗
DOE OSTI2023

Designing observables for quantum interference in jets at subleading color

The large-Nc or topologically planar limit of gauge theories can be considered as a classical limit because all gauge bosons are distinguishable particles and therefore cannot exhibit interference. Quantum effects due to the flow of color therefore arise starting at subleading in 1/Nc. We introduce kinematic observables explicitly sensitive to effects at subleading color formed from the ratio of interfering to squared color-ordered amplitudes. Such observables are in general not infrared and collinear safe, so we introduce angular observables defined from appropriate multi-point energy correlators motivated by the form of color-ordered amplitudes. We demonstrate that color interference effects are manifest as sinusoidal oscillation in the simplest system, a collinear jet with three particles, and show the limitations of predicting this observable in all-purpose, leading-color parton shower Monte Carlos.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
DOE OSTI2022

WALLABY Pre-pilot Survey: The Effects of Tidal Interaction on Radial Distribution of Color in Galaxies of the Eridanus Supergroup

We study the tidal interaction of galaxies in the Eridanus supergroup, using H i data from the pre-pilot survey of the Widefield ASKAP L-band Legacy All-sky Blind surveY. We obtain optical photometric measurements and quantify the strength of tidal perturbation using a tidal parameter S sum . For low-mass galaxies of M * ≲ 10 9 M ⊙ , we find a dependence of decreasing H i to optical disk size ratio with increasing S sum , but no dependence of H i spectral line asymmetry with S sum . This is consistent with the behavior expected under tidal stripping. We confirm that the color profile shape and color gradient depend on the stellar mass, but there is an additional correlation of low-mass galaxies having their color gradients within 2R 50 increasing with higher S sum . For these low-mass galaxies, the dependence of color gradients on S sum is driven by the color becoming progressively redder in the inner disk when tidal perturbations are stronger. For high-mass galaxies, there is no dependence of color gradients on S sum , and we find a marginal reddening throughout the disks with increasing S sum . Our result highlights tidal interaction as an important environmental effect in producing the faint end of the star formation suppressed sequence in galaxy groups.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1972

Theoretical aspects of color vision

The three color receptors of Young-Helmholtz and the opponent colors type of information processing postulated by Hering are both present in the human visual system. This mixture accounts for both the phenomena of color matching or hue discrimination and such perceptual qualities of color as the division of the spectrum into color bands. The functioning of the cells in the visual system, especially within the retina, and the relation of this function to color perception are discussed.

Wolbarsht, M. L.↗
NASA NTRS1973

The color bar phase meter: A simple and economical method for calibrating crystal oscillators

Comparison of crystal oscillators to the rubidium stabilized color burst is made easy and inexpensive by use of the color bar phase meter. Required equipment consists of an unmodified color TV receiver, a color bar synthesizer and a stop watch (a wrist watch or clock with sweep second hand may be used with reduced precision). Measurement precision of 1 x 10 to the minus 10th power can be realized in measurement times of less than two minutes. If the color bar synthesizer were commercially available, user cost should be less than $200.00, exclusive of the TV receiver. Parts cost for the color bar synthesizer which translates the crystal oscillator frequency to 3.579MHz and modulates the received RF signal before it is fed to the receiver antenna terminals is about $25.00. A more sophisticated automated version, with precision of 1 x 10 to the minus 11th power would cost about twice as much.

Davis, D. D.↗
NASA NTRS1975

Mean colors of Cepheids

Color observations of Cepheids can be interpreted by a color effective temperature relation to give different T sub e values for each kind of mean color. Here, theoretical colors from numerical integrations of Cepheid pulsations are used to determine the proper method of taking the color mean in order to get, by the color T sub e relation, the correct nonpulsating T sub e.

Cox, A. N.↗
NASA NTRS1979

Application of multispectral color photography to flame flow visualization

For flames of short duration and low intensity of radiation a spectroscopical flame diagnostics is difficult. In order to find some other means of extracting information about the flame structure from its radiation, the feasibility of using multispectral color photography was successfully evaluated. Since the flame photographs are close-ups, there is a considerable parallax between the single images, when several cameras are used, and additive color viewing is not possible. Each image must be analyzed individually, it is advisable to use color film in all cameras. One can either use color films of different spectral sensitivities or color films of the same type with different color filters. Sharp cutting filters are recommended.

Stoffers, G.↗
NASA NTRS1980

A color-ratio map of Mercury

Orange and UV frames are used to construct a color-ratio map of the portion of Mercury imaged by Mariner 10, with at least two independent color-ratio images being used for each region in order to prevent spurious, blemish-induced color. Color differences appear to be smaller than those of the moon, and many apparently fresh craters and their ray systems tend to be bluer than their surroundings. Regions of interesting color contrast are noted, and it is concluded that there is little evident correlation of color with either geology or topography.

Hapke, B.↗
NASA NTRS1982

Color visualization for fluid flow prediction

High-resolution raster scan color graphics allow variables to be presented as a continuum, in a color-coded picture that is referenced to a geometry such as a flow field grid or a boundary surface. Software is used to map a scalar variable such as pressure or temperature, defined on a two-dimensional slice of a flow field. The geometric shape is preserved in the resulting picture, and the relative magnitude of the variable is color-coded onto the geometric shape. The primary numerical process for color coding is an efficient search along a raster scan line to locate the quadrilteral block in the grid that bounds each pixel on the line. Tension spline interpolation is performed relative to the grid for specific values of the scalar variable, which is then color coded. When all pixels for the field of view are color-defined, a picture is played back from a memory device onto a television screen.

Smith, R. E.↗
NASA NTRS1981

Color and temperature signatures of ocean fronts observed with the Nimbus-7 CZCS

The Nimbus-7 Coastal Zone Color Scanner has a unique capability for imaging simultaneously the optical (ocean color) and surface temperature (thermal infrared) signatures of ocean fronts. Examples of such color and temperature visualizations of some ocean fronts delineate virtually identical morphology. In other cases, however, the two signatures are displaced horizontally by tens of km, and display markedly different morphology and fine structure. For example, an image of the Gulf Stream's north wall over the Grand Banks shows the sharpest color front to occur approximately 50 km away from the sharpest temperature front. Moreover, the fine structure of the color front is qualitatively suggestive of disorganized turbulent diffusion, whereas that of the thermal front shows distinctive shear instabilities. These differences can occur because the infrared temperature image represents the top 0.05 millimeter of the sea surface, whereas the ocean color image represents the upper meters to decameters of the sea.

Mueller, J. L.↗
NASA NTRS1985

Color measurement and discrimination

Theories of color measurement attempt to provide a quantative means for predicting whether two lights will be discriminable to an average observer. All color measurement theories can be characterized as follows: suppose lights a and b evoke responses from three color channels characterized as vectors, v(a) and v(b); the vector difference v(a) - v(b) corresponds to a set of channel responses that would be generated by some real light, call it *. According to theory a and b will be discriminable when * is detectable. A detailed development and test of the classic color measurement approach are reported. In the absence of a luminance component in the test stimuli, a and b, the theory holds well. In the presence of a luminance component, the theory is clearly false. When a luminance component is present discrimination judgements depend largely on whether the lights being discriminated fall in separate, categorical regions of color space. The results suggest that sensory estimation of surface color uses different methods, and the choice of method depends upon properties of the image. When there is significant luminance variation a categorical method is used, while in the absence of significant luminance variation judgments are continuous and consistant with the measurement approach.

Wandell, B. A.↗
NASA NTRS1986

Multi-color incomplete Cholesky conjugate gradient methods for vector computers

In this research, we are concerned with the solution on vector computers of linear systems of equations, Ax = b, where A is a larger, sparse symmetric positive definite matrix. We solve the system using an iterative method, the incomplete Cholesky conjugate gradient method (ICCG). We apply a multi-color strategy to obtain p-color matrices for which a block-oriented ICCG method is implemented on the CYBER 205. (A p-colored matrix is a matrix which can be partitioned into a pXp block matrix where the diagonal blocks are diagonal matrices). This algorithm, which is based on a no-fill strategy, achieves O(N/p) length vector operations in both the decomposition of A and in the forward and back solves necessary at each iteration of the method. We discuss the natural ordering of the unknowns as an ordering that minimizes the number of diagonals in the matrix and define multi-color orderings in terms of disjoint sets of the unknowns. We give necessary and sufficient conditions to determine which multi-color orderings of the unknowns correpond to p-color matrices. A performance model is given which is used both to predict execution time for ICCG methods and also to compare an ICCG method to conjugate gradient without preconditioning or another ICCG method. Results are given from runs on the CYBER 205 at NASA's Langley Research Center for four model problems.

Poole, E. L.↗
NASA NTRS1988

Color and population gradients in the core of the postcollapse globular cluster M30

A new technique has been developed for seeking color gradients in multicolor CCD images of a globular cluster. Application of this technique to M30 confirms the radial color gradient reported by others. The B - V and V - R colors show linear gradients, when plotted against log r, that are many times their statistical errors. In the radial range 3-100 arcsec, the B - V and V - R colors increase outwards by about (0.18 + or - 0.015) mag/dex and (0.09 + or - 0.01) mag/dex, respectively. Color-magnitude arrays of the central region show that the Balmer-line strength that accompanies the central blueness is due to an increased proportion of blue-horizontal-branch starlight in the center. This excess does not appear to be statistically significant in terms of star numbers, even though the color gradient is so highly significant.

Piotto, Giampaolo↗