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The persistent shadow of the supermassive black hole of M87. II. Model comparisons and theoretical interpretations
The Event Horizon Telescope (EHT) observation of M87∗ in 2018 has revealed a ring with a diameter that is consistent with the 2017 observation. The brightest part of the ring is shifted to the southwest from the southeast. In this paper, we provide theoretical interpretations for the multi-epoch EHT observations for M87∗ by comparing a new general relativistic magnetohydrodynamics model image library with the EHT observations for M87∗ in both 2017 and 2018. The model images include aligned and tilted accretion with parameterized thermal and nonthermal synchrotron emission properties. The 2018 observation again shows that the spin vector of the M87∗ supermassive black hole is pointed away from Earth. A shift of the brightest part of the ring during the multi-epoch observations can naturally be explained by the turbulent nature of black hole accretion, which is supported by the fact that the more turbulent retrograde models can explain the multi-epoch observations better than the prograde models. The EHT data are inconsistent with the tilted models in our model image library. Assuming that the black hole spin axis and its large-scale jet direction are roughly aligned, we expect the brightest part of the ring to be most commonly observed 90 deg clockwise from the forward jet. This prediction can be statistically tested through future observations.
Enhanced shadow tomography of molecular excited states via the enforcement of N -representability conditions by semidefinite programming
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Ring Shadowing Effects on Saturn's Ionosphere: Implications for Ring Opacity and Plasma Transport
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NEW APPLICATIONS OF LUNAR SHADOW STUDIES
Variation of percentage of lunar shaded regions with changing elevation of sun
Photocell shadowing technique improves light source detector
Lightweight, compact modular system that includes an acquisition photocell is used as a light source tracking detector that exhibits minimum scale factor change with increased light source angle. Photocells of various types, responsive to other portions of the spectrum, could be used to acquire and track infrared, ultraviolet, and other source fluxes.
Determination of footpad penetration depth from Surveyor spacecraft shadows
Optical triangulation method for determining lunar surface elevation relative to Surveyor spacecraft
Observations of lunar shadowing of energetic particles.
Solar electron flux decreases observed by AIMP 2 and IMP 4 shown due to shielding by moon of energetic particles along field line
Time, Shadows, Terrain and Photointerpretation
Simulated aerial photography to enhance photointerpretation of terrain at various sun angles
Application of transport techniques to the analysis of NERVA shadow shields
A radiation shield internal to the NERVA nuclear rocket reactor required to limit the neutron and photon radiation levels at critical components located external to the reactor was evaluated. Two significantly different shield mockups were analyzed: BATH, a composite mixture of boron carbide, aluminum and titanium hydride, and a borated steel-liquid hydrogen system. Based on the comparisons between experimental and calculated neutron and photon radiation levels, the following conclusions were noted: (1) The ability of two-dimensional discrete ordinates code to predict the radiation levels internal to and at the surface of the shield mockups was clearly demonstrated. (2) Internal to the BATH shield mockups, the one-dimensional technique predicted the axial variation of neutron fluxes and photon dose rates; however, the magnitude of the neutron fluxes was about a factor of 1.8 lower than the two-dimensional analysis and the photon dose rate was a factor of 1.3 lower.
Graphics shadowing analysis
Visual image is generated on cathode-ray tube screen to scale and is constructed according to dimensions of specified craft. Once displayed, image may be manipulated by several different means.
Design computations for a nuclear rocket shadow shield
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Shadow mask for X-ray spectrometer
Imaging technique may be used in series with flat or conical Bragg crystals to separate spatial/spectral convolution when spectrometer is scanned across extended source emitting at more than one wavelength. Technique allows line direction and continuum to be detected and provides data for spatial mapping of source.
When day is done and shadows fall, we miss the airport most of all
Both the effectiveness of pilot training and the safety of flight can be influenced by the distribution of texture in the visual scene, the distance to which the eyes accommodate, and the associated shifts in the apparent size and distance of objects in central and peripheral vision. Studies reviewed and original results presented indicate that these factors are involved in various misjudgments and illusions experienced by pilots: (1) when searching for other airborne traffic or targets, (2) when making approaches to airports over water at night, (3) when breaking out of low clouds on a final approach to a landing by reference to head-up or head-down displays, and (4) when practicing simulated approaches and landings or air-to-surface weapon deliveries by reference to synthetically generated visual systems.
Remarkable modification of light curves for shadowing effects on irregular surfaces - The case of the asteroid 37 Fides
Photometric observations of the asteroid 37 Fides carried out at four observatories are reported. The data were taken at phase angles ranging from approximately 2-23 deg. A composite of the light curves obtained revealed that, considering a period of 7.33 hr, the full cycle light curve exhibits one maximum and one minimum. An increase in brightness was observed following a primary minimum, a factor that indicated the cyclical appearance and disappearance of a large topographical feature. It is concluded that the 7.33 hr period is the rotational speed of the asteroid, in contrast with a previously held 14.66 hr rotational period. The method is concluded useful for identifying rotational periods of asteroids when only partial light curve data from different sources is available, and when the projections can be checked observationally.
Solar reflection from interacting and shadowing cloud elements
An attempt is made to relate the reflection from a broken cloud field to that from a plane parallel cloud of the same optical properties by using Monte Carlo simulations for a very simple model of an array of regularly spaced, infinitely long bar clouds. Reflection from the array is represented by an effective cloud fraction, and it is shown that for many cases this may be obtained by treating the cloud elements to be noninteracting azimuthally symmetric reflectors. The effective cloud fraction is a function of solar zenith angle, the aspect ratio of the individual cloud elements, and the normal or zenith cloud fraction of the array. Model computations for reflection from an array of randomly distributed identical cylinders are also presented as an example of a possible application of this technique.