共查询到20条相似文献，搜索用时 78 毫秒
1.
A. Dob 《Astronomische Nachrichten》1981,302(2):93-98
Using merely mathematical means the author points out that in case of planets the Titius-Bode Law actully states, that if considering the distance between the Sun and the Earth as a unit, the mean-distance of any planet being farther than Mercury can be obtained if 0.4 is substracted from the double of the mean distance of the preceding planet. But in reality the fact is that for planets not the immediate preceding one mean-distance but the immediate preceding two mean-distances must be known in determining a mean-distance. The conformity between the measured values and those calculated by the Law and – in case of Neptune and Pluto – the discrepancy between them, stem from this fact. If in case of planets we consider not one, but two preceding mean-distances, a ”︁correction” will occur in the formula obtained which eliminates the considerable discrepancy. In case of satellites it is enough to know the immediate preceding one mean-distance which means, that the application of the Titius-Bode Law proves successful. 相似文献
2.
We have tested the implications and limitations of Program ACRETE, a scheme based merely on Newtonian physics and accretion with unit sticking efficiency, devised by Dole in 1970 to simulate the origin of the planets. The dependence of the results on a variety of radial and vertical density distribution laws, on the ratio of gas to dust in the solar nebula, on the total nebula mass, and on the orbital eccentricity, ?, of the accreting grains are explored. Only for a small subset of conceivable cases are planetary systems closely like our own generated. Many models have tendencies toward one of two preferred configurations: multiple-star systems, or planetary systems in which Jovian planets either have substantially smaller masses than in our system or are absent altogether. But for a wide range of cases recognizable planetary systems are generated, ranging from multiple-star systems with accompanying planets, to systems with Jovian planets at several hundred astronomical units, to single stars surrounded only by asteroids. Many systems exhibit planets like Pluto and objects of asteroidal mass, in addition to usual terrestrial and Jovian planets. No terrestrial planets were generated more massive than five Earth masses. The number of planets per system is for most cases of order 10, and, roughly, inversely proportional to ?. All systems generated obey a relation of the Titius-Bode variety for relative planetary spacing. The case with which planetary systems are generated using such elementary and incomplete physical assumptions supports the idea of abundant and morphologically diverse planetary systems throughout the Galaxy. 相似文献
3.
S. Alan Stern 《Celestial Mechanics and Dynamical Astronomy》1989,47(3):267-273
We investigate the potential importance of molecular cloud and stellar perturbations on the orbits of Pluto and more distant (hypothetical) planets up to 500 AU from the Sun. It is found that stellar and molecular cloud-core perturbations are of roughly equal importance. It also is found that the likelihood of substantial perturbations on Pluto is not insignificant, and that numerous substantial stellar and molecular cloud perturbations are likely to have influenced the orbits of any planets beyond 200 AU. These perturbations may contribute to a prevalence of moderate eccentricities and inclinations for planets beyond the orbit of Neptune, and may be a characteristic of distant planetary orbits in other solar systems. Given the recent discovery of chaotic behavior in Pluto's orbit (Sussman and Wisdom 1988), the effects of external perturbations on the long-term stability of Pluto's orbit warrant continued study. 相似文献
4.
L. V. Ksanfomality 《Solar System Research》2016,50(1):67-80
In recent decades, investigations of Pluto with up-to-date astronomical instruments yielded results that have been generally confirmed by the New Horizons mission. In 2006, in Prague, the General Assembly of the International Astronomical Union (IAU) reclassified Pluto as a member of the dwarf planet category according to the criteria defined by the IAU for the term “planet”. At the same time, interest in studies of Pluto was increasing, while the space investigations of Pluto were delayed. In 2006, the New Horizons Pluto spacecraft started its journey to Pluto. On July 14, 2015, the spacecraft, being in fly-by mode, made its closest approach to Pluto. The heterogeneities and properties of the surface and rarified atmosphere were investigated thoroughly. Due to the extreme remoteness of the spacecraft and the energy limitations, it will take 18 months to transmit the whole data volume. Along with the preliminary results of the New Horizons Pluto mission, this paper reviews the basics on Pluto and its moons acquired from the ground-based observations and with the Hubble Space Telescope (HST). There are only a few meteorite craters on the surfaces of Pluto and Charon, which distinctly marks them apart from such satellites of the giant planets as Ganymede and Callisto. The explanation is that the surface of Pluto is young: its age is estimated at less than 100 Myr. Ice glaciers of apparently a nitrogen nature were found. Nitrogen is also the main component of the atmosphere of Pluto. The planet demonstrates the signs of strong geologic activity, though the energy sources of these processes are unknown. 相似文献
5.
The hypersonic analog for the interaction of the solar wind with Jupiter, Saturn, Uranus, Neptune and Pluto is used to provide estimates of shock shapes and locations as well as average magnetosheath and/or ionosheath properties for these planets. Several representative spacecraft flyby trajectories (designed for outer-planet Grand Tour simulations) are superimposed upon a series of figures in order to provide estimates of potential plasma and field parameters which may be encountered. Consideration is given first to the possibility that several of these planets have intrinsic magnetic fields and, secondly, to the interaction of the solar wind directly on the ionosphere should there actually be no intrinsic field. Saturn and Pluto are chosen as examples of this latter case. 相似文献
6.
A sample of 145 galaxies having radial velocities relative to the centroid of the Local Group V
LG < 500 km/sec and estimated photometric distances D < 8 Mpc is considered. The field of peculiar velocities of these galaxies is estimated using the tensor of the local value of the Hubble constant H
ij
, with principal values of 81:62:48 in km/sec·Mpc, which have a standard error of 4 km/sec·Mpc. The minor axis of the Hubble ellipsoid is oriented almost along the polar axis of the Local Supercluster, while the major axis forms an angle = (29 ± 5)° with the direction toward the center of the Virgo Cluster. Such a configuration of the peculiar-velocity field shows unsatisfactory agreement with the model of a spherically symmetric flow of galaxies toward the Virgo Cluster. Rotation of the Local Supercluster may be one reason for this difference. The peculiar velocities of galaxies within a volume with D < 8 Mpc are characterized by a dispersion
V
= 74 km/sec, a considerable part of which is due to the virial motions of galaxies in groups and to distance errors. For field galaxies, located in a layer of 1 < D < 3 Mpc around the Local Group, the radial-velocity dispersion does not exceed 25 km/sec. The velocity—distance relation, constructed from the 20 closest galaxies around the Local Group with D < 3 Mpc and with errors (D) < 0.2 Mpc, exhibits the expected effect of gravitational deceleration. Using the estimate of R
0 = (0.96 ± 0.05) Mpc for the observed radius of the zero-velocity sphere, we determined the total mass of the Local Group to be (1.2 ± 0.2)·1012
M
, which agrees well with the sum of the virial masses of the subgroups of galaxies around the Local Group and M31. The ratio of the Local Group's total mass (within R
0) to its luminosity is M/L = (23 ± 4) M
/L
, which does not require the existence of supermassive dark halos around our Galaxy and M31. 相似文献
7.
V. A. Kotov 《Bulletin of the Crimean Astrophysical Observatory》2007,103(1):75-81
In 1946, E. Sevin postulated the global vibrations of the Sun with a period P 0 = 1/9 day and a “wavelength” L 0 = c × P 0 = 19.24 AU and predicted the tenth planet at a mean distance of 4.0 × L 0 ≈ 77.0 AU from the Sun (c is the speed of light). The global vibrations of the Sun, precisely with the period of 1/9 day, were actually detected in 1974. Recently, the largest Kuiper Bell object 2003 UB313, or Eris, with an orbital semimajor axis ≈ 3.5 × L 0 ≈ 67.5 AU was discovered. We adduce arguments for the status of Eris as our tenth planet: (i) the object is larger and farther from the Sun than Pluto and (ii) the semimajor axis of Eris agrees well with the sequence of planetary distances that follows from the resonance spectrum of the Solar system dimensions (with the scale L 0 and for all 11 orbits, including those of Pluto, Eris, and the asteroid belt). We point to a mistake of the Prague (2006) IAU Assembly, which excluded Pluto from the family of planets by introducing a new, highly controversial class of objects—“dwarf planets.” 相似文献
8.
We have identified 22 galaxies with photometric redshifts zph=5–7 in the northern and southern Hubble Space Telescope deep fields. An analysis of the images of these objects shows that they are asymmetric and very compact (～1 kpc) structures with high surface brightness and absolute magnitudes of MB≈?20m. The average spectral energy distribution for these galaxies agrees with the distributions for galaxies with active star formation. The star formation rate in galaxies with zph=5–7 was estimated from their luminosity at λ=1500 Å to be ~30 M⊙yr?1. The spatial density of these objects is close to the current spatial density of bright galaxies. All the above properties of the distant galaxies considered are very similar to those of the so-called Lyman break galaxies (LBGs) with z ～ 3–4. The similarity between the objects considered and LBGs suggests that at z ～6, we observe the progenitors of present-day galaxies that form duringmergers of protogalactic objects and that undergo intense starbursts. 相似文献
9.
A. G. Mavraganis 《Astrophysics and Space Science》1975,34(2):395-401
The hypothesis on the -ray burst generation in the process of the collapse of surpermassive bodies in the nuclei of active galaxies is considered. It is shown that -ray burst properties observed may be interpreted within the frames of the given model. A statistical test for choosing a hypotheses on -ray burst nature is discussed. 相似文献
10.
It has become part of the conventional wisdom of quasar research that quasars cannot be objects ejected from nearby galaxies.
The reasons are summarized in Burbidge & Burbidge (1967) and they include: (1) in quasar spectra only redshifts, and no blueshifts,
are observed, contrary to expectation in a local Doppler interpretation of quasar line shifts; (2) the energy requirements
for relativistically moving quasars seem excessive and the ejection mechanism is unknown. In. this work we show that the first
problem could be explained via some powerful selection effects, and that the second problem does not exist in the relativistic
slingshot process of ejecting black holes. Consequently one cannot exclude the possibility that at least some of the quasar-galaxy
associations of large redshift differentials discussed by Arp and Sulentic are real and that the redshift differences are
due to high speeds of ejected quasars 相似文献
11.
Georgy Gladyshev 《Earth, Moon, and Planets》1978,18(2):217-221
The planets and their satellites are formed in accordance with similar mechanisms as a result of spatially periodic condensation of gaseous matter during the formation of the central body.Using the diffusion theory one can calculate the age of the planets and explain the nature of the Titius-Bode law. 相似文献
12.
Ekkehard Nowotny 《Earth, Moon, and Planets》1979,21(3):257-274
The linear density and velocity perturbations are analyzed in a differentially rotating thin gravitating disc consisting of gas and dust. For the radial behaviour of the equilibrium density and the velocity of sound we assume a power law. The zeros of these perturbations have a distance behaviour like the distances of the planets and their satellites known as the Titius-Bode rule. It is suggested, that the knots of the velocity disturbances are the places where ring like dust accumulations occur. The mechanism is the same as in the Kundt's tube, where collisions between the dust and the oscillating gas are responsible for this effect. 相似文献
13.
A catalog of asteroids in two-body orbital resonances with the planets of the Solar System has been created. The AstDyS database was a source of the input data, and all the numbered objects (467303 objects at the time of the analysis) were considered. The orbits were integrated in the framework of a pure gravitational problem considering all the planets of the Solar System and Pluto. From the analysis of the behavior of the resonant argument and the semimajor axis on the 100-kyr interval, the resonance membership and the libration type (pure or transient) were verified for each of the asteroids. A more accurate method to identify the resonant argument librations was developed on the basis of the analysis of mutual periodograms. We found 23251 resonant asteroids, ~36% of which (8397 objects) are in pure resonances. 相似文献
14.
Michael Martin Nieto 《Icarus》1975,25(1):171-174
Although it is by no means clear that the Titius-Bode law of planetary distances is indeed a “law” (even though there are enticing indications), it is proposed that if one assumes that the law is a “law” and that the planets obey it, then this argues against recent large-scale evolution in the solar system. Put another way: one can believe in the Titius-Bode law or in recent large-scale evolution or in neither of them. But it appears difficult to believe in both of them. 相似文献
15.
Elizabeth A. Corbett A. Robinson D. J. Axon S. Young & J. H. Hough 《Monthly notices of the Royal Astronomical Society》1998,296(3):721-738
We present spectropolarimetric observations of seven broad-line radio galaxies. We find significantly polarized broad Hα emission in four objects including two, Arp 102B and 3C 390.3, which have double-peaked line profiles. In these objects the prominent redshifted and blueshifted peaks of the broad Hα line have no clear counterparts in polarized flux. This conflicts with theoretical predictions for a relativistic line-emitting disc with an electron scattering atmosphere, one of the leading models advanced to account for the double-peaked lines. The shapes and widths of the polarized line profiles can be explained if, as expected in unified schemes, the scattering occurs near the poles of an obscuring torus. However, the observed polarization position angles favour geometries in which the scattering plane is perpendicular to the radio jet. A configuration in which Hα photons emitted by a biconical flow are scattered off the inner wall of the torus has this property, and would also produce a single-peaked scattered line profile. With the exception of 3C 227, the sample as a whole conforms to the general trend in powerful radio galaxies for the optical polarization to be aligned with the radio source axis, favouring toroidal rather than polar scattering. 相似文献
16.
Globulettes are small (radii \({<} 10\) kAU) dark dust clouds, seen against the background of bright nebulae. A majority of the objects have planetary mass. These objects may be a source of brown dwarfs and free floating planetary mass objects in the galaxy. In this paper we investigate how many globulettes could have formed in the Milky Way and how they could contribute to the total population of free floating planets. In order to do that we examine H-alpha images of 27 H II regions. In these images, we find 778 globulettes.We find that a conservative value of the number of globulettes formed is \(5.7\times 10^{10}\). If 10% of the globulettes form free floating planets then they have contributed with \(5.7\times 10^{9}\) free floating planets in the Milky Way. A less conservative number of globulettes would mean that the globulettes could contribute \(2.0\times 10^{10}\) free floating planets. Thus the globulettes could represent a non-negligible source of free floating planets in the Milky Way. 相似文献
17.
The photoelectric spectrophotometry of nine Be stars is performed. Their monochromatic absolute magnitudes derived in the wavelength range 3200–8000 Å are presented. The energy distribution curves obtained are calibrated for effective temperatures with the aid of the synthetic stellar atmospheres. 相似文献
18.
L. Bassani R. C. Butler A. J. Dean G. Di Cocco F. Perotti G. Villa 《Astrophysics and Space Science》1982,82(1):199-207
Three active galaxies, generally classified as Seyferts, have been discovered recently to be powerful, low energy -ray sources. The similarity between their spectral characteristics and those of the cosmic background at -ray energies suggests that these objects could make a significant contribution to this diffuse flux. This contribution has been assessed using two different number densities of -ray-emitting Seyfert galaxies based on optical and X-ray data. The comparison of the estimated and measured diffuse -ray background intensities is used to gain a deeper understanding of the metabolism of Seyfert galaxies. 相似文献
19.
Loretta Dunne Stephen A. Eales 《Monthly notices of the Royal Astronomical Society》2001,327(3):697-714
This is the second in a series of papers presenting results from the SCUBA Local Universe Galaxy Survey. In our first paper we provided 850-μm flux densities for 104 galaxies selected from the IRAS Bright Galaxy Sample and we found that the 60-, 100-μm ( IRAS ) and 850-μm (SCUBA) fluxes could be adequately fitted by emission from dust at a single temperature. In this paper we present 450-μm data for the galaxies. With the new data, the spectral energy distributions of the galaxies can no longer be fitted with an isothermal dust model – two temperature components are now required. Using our 450-μm data and fluxes from the literature, we find that the 450/850-μm flux ratio for the galaxies is remarkably constant, and this holds from objects in which the star formation rate is similar to our own Galaxy, to ultraluminous infrared galaxies (ULIRGs) such as Arp 220. The only possible explanation for this is if the dust emissivity index for all of the galaxies is ∼2 and the cold dust component has a similar temperature in all galaxies . The 60-μm luminosities of the galaxies were found to depend on both the dust mass and the relative amount of energy in the warm component, with a tendency for the temperature effects to dominate at the highest L 60 . The dust masses estimated using the new temperatures are higher by a factor of ∼2 than those determined previously using a single temperature. This brings the gas-to-dust ratios of the IRAS galaxies into agreement with those of the Milky Way and other spiral galaxies which have been intensively studied in the submm. 相似文献
20.
In order to see whether the study of redshift distribution in different classes of extragalactic objects, suspected of belonging to different phases in the evolutionary sequence of galaxies, helps in arriving at a possible picture of the evolutionary sequence of galaxies, histograms have been plotted between the number and the redshift for each of the five classes of extragalactic objects, namely, the QSOs, N-galaxies, Seyfert galaxies, radio galaxies and normal galaxies. It is found that: (i) the highest peaks in the five histograms occur at distinctly different redshifts in the order (Z
peak)QSOs>(Z
peak)N-galaxies>(Z
peak)Seyfert galaxies>(Z
peak)radio galaxies> (Z
peak)normal galaxies and (ii) sufficient overlap occurs in the redshift ranges of (a) QSOs and N-galaxies, (b) N-galaxies and Seyfert galaxies, (c) Seyfert galaxies and radio galaxies and (d) radio galaxies and normal galaxies. These facts suggest that the extragalactic objects might be evolving in the sequence: QSOsN-galaxiesSeyfert galaxiesradio galaxiesnormal galaxies. Other independent evidences in support of such an evolutionary sequence have been given. Finally, various aspects of the problem associated with the picture of the evolutionary sequence of galaxies have been critically examined. 相似文献