117,722 research outputs found
The Hubble Wide Field Camera 3 Test of Surfaces in the Outer Solar System: The Compositional Classes of the Kuiper Belt
We present the first results of the Hubble Wide Field Camera 3 Test of
Surfaces in the Outer Solar System (H/WTSOSS). The purpose of this survey was
to measure the surface properties of a large number of Kuiper belt objects and
attempt to infer compositional and dynamical correlations. We find that the
Centaurs and the low-perihelion scattered disk and resonant objects exhibit
virtually identical bifurcated optical colour distributions and make up two
well defined groups of object. Both groups have highly correlated optical and
NIR colours which are well described by a pair of two component mixture models
that have different red components, but share a common neutral component. The
small, high-perihelion excited objects are entirely
consistent with being drawn from the two branches of the mixing model
suggesting that the colour bifurcation of the Centaurs is apparent in all small
excited objects. On the other hand, objects larger than are
not consistent with the mixing model, suggesting some evolutionary process
avoided by the smaller objects. The existence of a bifurcation amongst all
excited populations argues that the two separate classes of object existed in
the primordial disk before the excited Kuiper belt was populated. The cold
classical objects exhibit a different type of surface which has colours that
are consistent with being drawn from the red branch of the mixing model, but
with much higher albedos.Comment: Accepted to the Astrophysical Journal. 49 Pages, 15 Figure
High energy electron spikes at high latitudes
Over 750 spikes of precipitating electrons with E or = 425 KeV were observed aboard the low altitude polar orbiter OGO-D between 30 July 1967 and 31 December 1967. The spikes may be divided into three distinct populations, depending on whether they occur at latitudes below, at, or above the local limit of trapping
Comparison of Models of Critical Opacity in the Quark-Gluon Plasma
In this work we discuss two methods of calculation of quark propagation in
the quark-gluon plasma. Both methods make use of the Nambu-Jona-Lasinio model.
The essential difference of these calculations is the treatment of
deconfinement. A model of confinement is not included in the work of Gastineau,
Blanquier and Aichelin [hep-ph/0404207], however, the meson states they
consider are still bound for temperatures greater than the deconfinement
temperature T_c. On the other hand, our model deals with unconfined quarks and
includes a description of the q(bar)q resonances found in lattice QCD studies
that make use of the maximum entropy method (MEM). We compare the q{bar)q cross
sections calculated in these models.Comment: 7 pages and 4 figures RevTe
Water ice in the Kuiper belt
We examine a large collection of low-resolution near-infrared spectra of Kuiper Belt objects (KBOs) and centaurs in an attempt to understand the presence of water ice in the Kuiper Belt. We find that water ice on the surface of these objects occurs in three separate manners: (1) Haumea family members uniquely show surfaces of nearly pure water ice, presumably a consequence of the fragmentation of the icy mantle of a larger differentiated proto-Haumea; (2) large objects with absolute magnitudes of H < 3 (and a limited number to H = 4.5) have surface coverings of water iceāperhaps mixed with ammoniaāthat appears to be related to possibly ancient cryovolcanism on these large objects; and (3) smaller KBOs and centaurs which are neither Haumea family members nor cold-classical KBOs appear to divide into two families (which we refer to as "neutral" and "red"), each of which is a mixture of a common nearly neutral component and either a slightly red or very red component that also includes water ice. A model suggesting that the difference between neutral and red objects due to formation in an early compact solar system either inside or outside, respectively, of the ~20 AU methanol evaporation line is supported by the observation that methanol is only detected on the reddest objects, which are those which would be expected to have the most of the methanol containing mixture
G conditioning suit Patent
Conditioning suit for normal function of astronaut cardiovascular system in gravity environmen
Assessment of risk to Boeing commerical transport aircraft from carbon fibers
The possible effects of free carbon fibers on aircraft avionic equipment operation, removal costs, and safety were investigated. Possible carbon fiber flow paths, flow rates, and transfer functions into the Boeing 707, 727, 737, 747 aircraft and potentially vulnerable equipment were identified. Probabilities of equipment removal and probabilities of aircraft exposure to carbon fiber were derived
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