Variations of the Earth's albedo deduced from the ashen light of the Moon

An analysis of 1210 visual brightness estimations of the Moon's ashen light is presented, performed by a working group of amateur astronomers from June 1972 to December 1973. In the Moon phase interval 0.1 T _b 0.7 the brightness expressed in a semi-empirical scale, S _G, is found to be linearly related to the phase. Monthly deviations from the mean brightness show well defined winter maxima (January) and summer minima (July). Within the referenced period the brightness of the ashen light tends to increase, whereas the solar magnetic activity decreased. In addition, minor correlations and, respectively, anti-correlations are found at stratospheric temperature and, respectively density. On account of the nature of the ashen light its variations are regarded as fluctuations of the Earth's albedo.     

Influence of the layered Moon and Earth's orientation on lunar rotation

One of the most efficient ways to probe the lunar inner structure at present is through the study of its rotation.Range and range rate(Doppler) data between the Chang'E-3 lander and station on the Earth were collected from the beginning of the Chang'E-3 lunar mission in 2013.These observation data,taken together with the existing lunar laser ranging data,provide a new approach to extend research on the Earth-Moon system.The high precision of current observation data imposes exacting demands,making it necessary to include previously neglected factors.In this paper,motivated by progress of the Chinese lunar exploration project and to use its data in the near future,two lunar models:a one-layer model and a two-layer model with a fluid core,were applied to the rotational equations based on our implemented algorithm of the Moon's motion.There was a difference of about 0.5′′in φ and ψ,but 0.2′′in θ between the two models.This result confirms that stratification of the inner structure of the Moon can be inferred from rotation data.We also added precise Earth rotation parameters in our model;the results show that this factor is negligible at present,due to the limited precision of the existing data.These results will help us understand the rotational process clearly and build a more realistic Earth-Moon model when we combine Lunar Laser Ranging data with high precision radio data to fit lunar motion in the near future.     

Origin of the Moon — Capture by gas drag of the Earth's primordial atmosphere

We propose a new scenario of the lunar origin, which is a natural extension of planetary formation processes studied so far by us in Kyoto. According to these studies, the Earth grew up in a gaseous solar nebula and, consequently, the sphere of its gravitational influence (i.e., the Hill sphere of the Earth) was filled by a gas forming a dense primordial atmosphere of the Earth. In the later stages, this atmosphere as well as the solar nebula was dissipated gradually, owing to strong activities of the early-Sun in a T Tauri-stage.In the present and the subsequent papers, we study a series of dynamical processes where a lowenergy (i.e., slightly unbound) planetisimal is trapped within the terrestrial Hill sphere, under the above-mentioned circumstances that the gas density of the primordial atmosphere is gradually decreasing. It is clear that two conditions must be satisfied for the lunar origin: first, an unbound planetesimal entering the Hill sphere have to dissipate its kinetic energy and come into a bound orbit before it escapes from the Hill sphere and, second, the bound planetisimal never falls onto the surface of the Earth.In this paper we study the first condition by calculating the oribital motion of a planetesimal in the Hill sphere, which is affected both by solar gravity and by atmospheric gas drag. The results show that a low-energy planetisimal with the lunar mass or less can be trapped in the Hill sphere with a high probability, if it enters the Hill sphere at stages before the atmospheric density is decreased to about 1/50 of the initial value.In the subsequent paper, the second condition will be studied and it will be shown that a tidal force, among other forces, is very important for a trapped planetesimal to avoid collision with the Earth and stay eternally in the Hill sphere as a satellite.     

Variations of the solid Earth's center of mass due to oceanic tides

Periodic variations in the location of the center of mass of the solid Earth due to ocean tides are derived from the ocean tide model of Seiler (1991). The sum of nine partial tides leads to changes in the coordinates X, Y, Z within a range of 1cm.     

Irregular Behavior in the Light Variations of 29 Cyg

After reviewing the general observational properties of the Lambda Bootis star 29 Cygni, we study samples of its light curve and apply the phase space and FFT tools to investigate the nature of its light curve irregularities. This revised version was published online in July 2006 with corrections to the Cover Date.     

Seasonal Variations in the North-South Asymmetry of Polarized Light of Jupiter

Over an 18-year period, seasonal changes in the north-south asymmetry of polarization at high latitudes of Jupiter have been revealed by polarimetric observations in blue light. The average seasonal difference in the polarization degree between north and south is positive and equal to about 0.5%. There is some relationship between seasonal variations in the observed difference and the seasonal north-south asymmetry in solar radiation incident on Jupiter's atmosphere. There are two maxima on the observed seasonal curve, falling on the jovian spring and autumn and coinciding correspondingly with positive and negative maxima of the heliographic latitude of Jupiter. Two possible explanations are discussed: seasonal changes in insolation and/or time-dependent magnetospheric influence on the polar events.     

Evaluation of Light Flashes Caused by Impacts of Small Comets on the Surface of the Moon

Images of the dayglow of the Earth's atmosphere in the ultraviolet wavelength region obtained by the photometer of the spacecraft Dynamics Explorer revealed dark spots of the order of 50 km in diameter. These atmospheric holes were interpreted by the American physicist Frank as concentrations of water vapor formed as a result of the disintegration and vaporization of so-called small comets at high altitudes. An analysis of the same images showed that their explanation requires a frequency of comet collisions with the Earth as high as 20 events a minute! This sensational hypothesis evoked a heated scientific debate. The paper below contains an analysis of the possibility of observing Frank's hypothetical comets during their collisions with the Moon. By solving a two-dimensional radiative–gasdynamic problem, the authors demonstrate that the flashes occurring during such impacts can be observed from the Earth with ordinary telescopes.     

Earth albedo and the orbit of Lageos

The long-period perturbations in the orbit of Lageos satellite due to the earth's albedo have been found using a new analytical formalism. The earth is assumed to be a sphere whose surface diffusely reflects sunlight according to Lambert's law. Specular reflection is not considered. The formalism is based on spherical harmonics; it produces equations which hold regardless of whether the terminator is seen by the satellite or not. Specializing in the case of a realistic zonal albedo shows that Lageos' orbital semimajor axis changes periodically by only about a centimeter and the eccentricity by two parts in 10⁵. The longitude of the node increases secularly by about 6×10^–4 arc sec yr^–1. The effect considered here can explain neither the secular decay of 1.1 mm day^–1 in the semimajor axis nor the observed along-track variations in acceleration of order 2×10^–12 ms^–2.     

A Study of Optical Light Variations of LINERs in SDSS

The Stripe82 has been repeatedly observed by SDSS (Sloan Digital Sky Survey) from 1998 to 2004, so as to provide us with opportunities to investigate the light variations of related objects. In this work, 29 broad-line LINERs (low-ionization nuclear emission line regions) in the Stripe82 are selected from the catalog LMCC (Light-Motion Curve Catalogue) to study their light variations. By comparing with the photometric measurements of the normal galaxies in LMCC, four candidates which possibly have light variations are picked up. Finally, after further veri?cations, it is found that there are two LINERs (SDSS J004828.80-001241.5 and SDSS J030203.53+005159.5) exhibiting relatively obvious light variations.     

狮子AD星的光电监测和宁静期光变

狮子AD(AD.Leo)是一个耀变十分频繁的耀星。本文通过对观测的分析,认为该星宁静期光度有高、低态之分,低态很可能是由大面积低温区引起的。     

An Analysis of the Radio Light Variations of Blazars With Low Peak Frequencies

The data of light variations of six blazars with low peak frequencies (i.e., BL Lacerta, 0235+164, OQ530, 0716+714, 3C 345, and 3C 273) at 4.8, 8, 14.5, 22 and 37 GHz in the recent thirty years have been collected from immense amount of literature. By using the method of discrete correlation function the correlations and delays of the light curves of these six sources at the 5 wavebands are analyzed. With the method of structural function, the periods and timescales of the light variations of these six sources are analyzed, and their amplitudes of light variations are compared and analyzed. As revealed by the result of analysis, among the six blazars the amplitudes of light variations of 0716+714 and 0235+164 are relatively large, and those of 3C 345 and OQ 530 are less. The amplitudes of light variations of 3C 273 and BL Lacertae are relatively smaller. As shown by the multi-waveband analysis of delays between two neighboring wavebands, 0235+164 exhibits the tendency of variation that the high-frequency wavebands precede the low-frequency wavebands. On the whole, 3C 345 exhibits the tendency that the high-frequency wavebands lag be-hind the low-frequency wavebands. The analyses of the other blazars show that in a part of radio wavebands there appears the tendency of variation that the high-frequency waveband leads the low-frequency waveband. Yet in the other radio wavebands there appears the tendency that the high-frequency waveband lags behind the low-frequency waveband. As revealed by the results of analyses with the method of structural function, the timescale, fitted slope, and period of light variations of 3C 345 are larger than those of the other five blazars with low peak frequencies. This demonstrates that the activity of 3C 345 is comparatively weaker than the other five sources, and implies that in the interior of 3C 345 there may exist some physical processes which are different from those of the other five blazars with low peak frequencies.     

Analyses of the Light Variations of OJ 287, 0716+714 and BL Lacertae

OJ 287 is a BL Lac object which exhibits intense activities of low peak-frequencies. Its energy spectrum in low frequency band is quite similar with those of two other TeV BL Lac objects (i.e., 0716+714 and BL Lacertae). However, the Cerenkov telescope did not detect its TeV rays. By using the observational data of these three heavenly bodies and comparing the discrepan- cies of their minimal periods of light variations and delays at 22 GHz, 37 GHz and B-waveband, we have further investigated the possible reason why the TeV gamma-rays of OJ 287 have not been observed. The results of analyses are as fol- lows. (1) For the minimal periods of light variations, the periods of OJ 287 at 37 GHZ and B-waveband are short. At 22 GHz the results of OJ 287 and 0716+714 are comparable, but the period of OJ 287 is much shorter in comparison with that of BL Lacertae, and this shows that its activity is more intense. However, the TeV gamma-rays of OJ 287 have not been detected, which implies that the radiation of OJ 287 in TeV waveband may have no connection with the minimal periods of light variations in these three low-energy wavebands. (2) In respect of delays, the delay of OJ 287 in the B waveband with respect to 37 GHz is longer than that of 0716+714, but shorter than that of BL Lacertae. Its delay at 37 GHz in respect to 22 GHz is shorter than that of 0716+714. Meanwhile, the delay of BL Lacertae at 37 GHz in respect to 22 GHz is negative, which implies that 22 GHz precedes 37 GHz. Via the comparison and analysis of delays, no obvious differences between OJ 287 and 0716+714 as well as BL Lacertae have been found. On the side of energy spectra, it is quite possible that due to the steep energy spectrum of OJ 287 in TeV waveband, the Cerenkov telescope has not detected the gamma radiation of OJ 287. However, nowadays it is still not clear whether the steep energy spectrum in TeV energy range has some influence on the light variations in low energy realm.     

Variations of perturbations in perigee height with eccentricity for artificial Earth's satellites due to air drag

The variations of perturbations in perigee distance for different values of the orbital eccentricity for artificial Earth's satellites due to air drag have been studied. The analytical solution of deriving these perturbations, using the TD model (Total Density) have been applied, Helali (1987). The Theory is valid for altitudes ranging from 200 to 500 km above the Earth's surface and for solar 10.7 cm flux. Numerical examples are given to illustrate the variations of the perturbations in perigee distance with changing eccentricity (e < 0.2). A stronge perturbations in the perigee distance have been shown when the eccentricity in the range 0.001 <e < 0.05, especially for perigee distance 200 km.     

On the albedo of the interplanetary dust

The zodiacal light brightness and measured spatial density of the interplanetary dust lead to a mean geometric albedo of 0.24 for the dust particles near 1 AU; whereas the composition of collected micrometeroids suggests a geometric albedo ?0.1. The data do not support the very low albedo (?0.01) proposed by A. F. Cook [Icarus33 (1978), 349–360]. The evidence is against a change in the mean particle albedo between 0.1 and 2 AU. Beyond 2 AU the data are unclear and a change in albedo is not ruled out.     

A new treatment of the albedo radiation pressure in the case of a uniform albedo and of a spherical satellite

The purpose of this paper is to present a model for the radiation pressure acceleration of a spherical satellite, due to the radiation reflected by a planet with a uniform albedo. A particular choice of variables allows one to reduce the surface integrals over the lit portion of the planet visible to the satellite to one-dimensional integrals. Exact analytical expressions are found for the integrals corresponding to the case where the spacecraft does not "see" the terminator. The other integrals can be computed either numerically, or analytically in an approximate form. The results are compared with those of Lochry (1966). The model is applied to Magellan, a spacecraft orbiting Venus.