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113.
Julie Ziffer Humberto Campins Javier Licandro Noemi Pinilla-Alonso Yanga Fernandez Schelte J. Bus 《Earth, Moon, and Planets》2005,97(3-4):203-212
We present near infrared reflectance spectra from 0.8 to 2.5 μm of two asteroids with low Tisserand invariant, 1373 Cincinnati and 2906 Caltech. We compare our spectra with cometary nuclei and other asteroids in their class. Asteroids Cincinnati and Caltech have Tisserand invariant values of 2.72 and 2.97, respectively, values less than 3 are considered suggestive of cometary origin. The observed spectral slopes in the near-infrared are consistent with both the spectra of cometary nuclei and of primitive asteroids. However, both asteroids have features in the near-infrared that are not seen in cometary nuclei, but are present in other X-type asteroids. 1373 Cincinnati has a sharp slope change between 0.75 and 1.0 μm and 2906 Caltech has a broad and shallow absorption between 1.35 and 2.2 μm. Our attempts to model the visible and near-infrared spectrum of these two objects, with the components successfully used by Emery and Brown (2004, Icarus
164, 104–121) to fit Trojan asteroids, did not yield acceptable fits.Visiting Astronomer at the Infrared Telescope Facility, which is operated by the University of Hawaii under contract to the National Aeronautics and Space Administration. 相似文献
114.
Toshio Fukushima 《Celestial Mechanics and Dynamical Astronomy》1996,66(3):309-319
We developed two approximations of the Newton-Raphson method. The one is a sort of discretization, namely to search an approximate solution on pre-specified grid points. The other is a Taylor series expansion. A combination of these was applied to solving Kepler's equation for the elliptic case. The resulting method requires no evaluation of transcendental functions. Numerical measurements showed that, in the case of Intel Pentium processor, the new method is three times as fast as the original Newton-Raphson method. Also it is more than 2.5 times as fast as Halley's method, Nijenhuis's method, and others. 相似文献
115.
M. A. Vashkov’yak 《Astronomy Letters》2001,27(6):404-409
Data on three recently discovered satellites of Uranus are used to determine basic evolutional parameters of their orbits: the extreme eccentricities and inclinations, as well as the circulation periods of the pericenter arguments and of the longitudes of the ascending nodes. The evolution is mainly investigated by analytically solving Hill’s double-averaged problem for the Uranus-Sun-satellite system, in which Uranus’s orbital eccentricity e U and inclination i U to the ecliptic are assumed to be zero. For the real model of Uranus’s evolving orbit with e U≠0 and i U≠0, we refine the evolutional parameters of the satellite orbits by numerically integrating the averaged system. Having analyzed the configuration and dynamics of the orbits of Uranus’s five outer satellites, we have revealed the possibility of their mutual crossings and obtained approximate temporal estimates. 相似文献
116.
Christopher Packham Keith L. Thompson Almudena Zurita Johan H. Knapen Ian Smail Robert Greimel Daniel F. M. Folha Chris Benn rew Humphrey Rene Rutten David Ciardi Matthieu Bec Richard Bingham Simon Craig Kevin Dee Derek Ives Paul Jolley Peter Moore Marti Pi i Puig Simon Rees Gordon Talbot Sue Worswick 《Monthly notices of the Royal Astronomical Society》2003,345(2):395-405
117.
Using the teleparallel gravity versions of the Einstein and Landau–Lifshitz’s energy and/or momentum complexes, I obtain the
energy and momentum of the universe in viscous Kasner-type cosmological models. The energy and momentum components (due to
matter plus field) are found to be zero and this agree with a previous work of Rosen and Johri et al., who investigated the
problem of the energy in Friedmann–Robertson–Walker (FRW) universe. The result that the total energy and momentum components
of the universe in these models is zero same as Bergmann–Thomson’s energy–momentum and props the viewpoint of Tryon. Rosen
found that the energy of the FRW space–time is zero, which agrees with the studies of Tryon.
PACs Numbers: 04.20.-q; 04.50.+h
An erratum to this article is available at . 相似文献
118.
Recent data on the Tully–Fisher relation for spiral galaxies are compatible with the traditional correlation for astrophysical
systems, where the angular momentum varies as the square of the mass. Such a correlation is consistent with standard gravitational
theory, but is not explained by it. We here show that the noted relation follows from currently popular accounts of extended
or higher-dimensional gravitational theory. The latter also predicts that the spins of spirals should decay as the universe
expands, which can be tested by extending the Tully–Fisher data to higher redshifts. 相似文献
119.
We study the equilibrium points and the zero-velocity curves of Chermnykh’s problem when the angular velocity ω varies continuously and the value of the mass parameter is fixed. The planar symmetric simple-periodic orbits are determined numerically and they are presented for three values of the parameter ω. The stability of the periodic orbits of all the families is computed. Particularly, we explore the network of the families when the angular velocity has the critical value ω = 2√2 at which the triangular equilibria disappear by coalescing with the collinear equilibrium point L1. The analytic determination of the initial conditions of the family which emanate from the Lagrangian libration point L1 in this case, is given. Non-periodic orbits, as points on a surface of section, providing an outlook of the stability regions, chaotic and escape motions as well as multiple-periodic orbits, are also computed. Non-linear stability zones of the triangular Lagrangian points are computed numerically for the Earth–Moon and Sun–Jupiter mass distribution when the angular velocity varies. 相似文献
120.
R. Hanbury Brown 《Journal of Astrophysics and Astronomy》1984,5(1):19-30
The Chatterton Astronomy Department aims to apply interferometers with very high resolving power to optical astronomy. The
programme of the stellar intensity interferometer at Narrabri Observatory was completed in 1972 and since then the work has
been directed towards building a more sensitive instrument with higher resolving power. As a first step a much larger intensity
interferometer was designed but was not built because it was large, expensive and not as sensitive as desired. Efforts are
now being made to design a more sensitive and cheaper instrument. A version of Michelson’s stellar interferometer is being
built using modern techniques. It is hoped that it will reach stars of magnitude +8 and will work reliably in the presence
of atmospheric scintillation. It is expected to cost considerably less than an intensity interferometer of comparable performance.
The pilot model of this new instrument is almost complete and should be ready for test in 1984.
Text of an Academy Lecture delivered at the Raman Research Institute, Bangalore on January 27, 1984. 相似文献