139,427 research outputs found
The use of source and sink concepts in the calculation of wing characteristics at supersonic speeds
NICMOS Photometry of the Unusual Dwarf Planet Haumea and its Satellites
We present here Hubble Space Telescope NICMOS F110W and F160W observations of Haumea, and its two satellites Hi'iaka and Namaka. From the measured (F110W-F160W) colors of ā1.208 Ā± 0.004, ā1.48 Ā± 0.06, and ā1.4 Ā± 0.2 mag for each object, respectively, we infer that the 1.6 Ī¼m water-ice absorption feature depths on Hi'iaka and Namaka are at least as deep as that of Haumea. The light curve of Haumea is detected in both filters, and we find that the infrared color is bluer by ~2%-3% at the phase of the red spot. These observations suggest that the satellites of Haumea were formed from the collision that produced the Haumea collisional family
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
An analysis of performance estimation methods for aircraft
Measurements and analytical extrapolation validity in predicting full scale flight performance from model wind tunnel test
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
The Luminosity Function of the Hot and Cold Kuiper belt Populations
Abridged. We have performed an ecliptic survey of the Kuiper belt, with an
areal coverage of 8.9 square degrees to a 50% limiting magnitude of r'=24.7,
and have detected 88 Kuiper belt objects, roughly half of which received
follow-up one to two months after detection. Using this survey data alone, we
have measured the luminosity function of the Kuiper belt, thus avoiding any
biases that might come from the inclusion of other observations. We have found
that the Cold population defined as having inclinations less than 5 degrees has
a luminosity function slope alpha=0.82+-0.23, and is different from the Hot
population, which has inclinations greater than 5 degrees and a luminosity
function slope alpha=0.35+-0.21. As well, we have found that those objects
closer than 38 AU have virtually the same luminosity function slope as the Hot
population. This result, along with similar findings of past surveys
demonstrates that the dynamically cold Kuiper belt objects likely have a steep
size distribution, and are unique from all of the excited populations which
have much shallower distributions. This suggests that the dynamically excited
population underwent a different accretion history and achieved a more evolved
state of accretion than the cold population. As well, we discuss the
similarities of the Cold and Hot populations with the size distributions of
other planetesimal populations. We find that while the Jupiter family comets
and the scattered disk exhibit similar size distributions, a power-law
extrapolation to small sizes for the scattered disk cannot account for the
observed influx of comets. As well, we have found that the Jupiter Trojan and
Hot populations cannot have originated from the same parent popuation, a result
that is difficult to reconcile with scattering models similar to the NICE
model.Comment: Accepted for publication in Icarus. 27 pages, 10 figures, 4 table
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Conditioning suit for normal function of astronaut cardiovascular system in gravity environmen
Retention of a Primordial Cold Classical Kuiper Belt in an Instability-Driven Model of Solar System Formation
The cold classical population of the Kuiper belt exhibits a wide variety of
unique physical characteristics, which collectively suggest that its dynamical
coherence has been maintained through out the solar system's lifetime.
Simultaneously, the retention of the cold population's relatively unexcited
orbital state has remained a mystery, especially in the context of a solar
system formation model, that is driven by a transient period of instability,
where Neptune is temporarily eccentric. Here, we show that the cold belt can
survive the instability, and its dynamical structure can be reproduced. We
develop a simple analytical model for secular excitation of cold KBOs and show
that comparatively fast apsidal precession and nodal recession of Neptune,
during the eccentric phase, are essential for preservation of an unexcited
state in the cold classical region. Subsequently, we confirm our results with
self-consistent N-body simulations. We further show that contamination of the
hot classical and scattered populations by objects of similar nature to that of
cold classicals has been instrumental in shaping the vast physical diversity
inherent to the Kuiper belt.Comment: 9 pages, 11 figures, accepted for publication in Ap
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