共查询到20条相似文献，搜索用时 31 毫秒
1.
The near-infrared (0.65–2.5μm) spectral albedo of Jupiter and Saturn with 1.5% spectral resolution is presented for the center of disk and for the limb. There is a distinct difference in the continuum slope between Jupiter and Saturn which may be attributed to a difference in the dust content or composition of the two atmospheres. There is an indication of limb brightening in the deepest CH4 bands on Saturn. No limb brightening is found for Jupiter. 相似文献
2.
Dale W. Smith 《Icarus》1975,25(3):447-451
Brinkmann (1973) has suggested that the Galilean satellites might briefly manifest a brightening at mid-eclipse due to a concentration of light refracted into the geometric umbra of Jupiter by the atmosphere around the terminator. Results obtained using two different models of the Jovian atmosphere indicate that such a brightening is unlikely even for Callisto due to the probable aerosol concentration in the Jovian atmosphere at the relevant altitudes. 相似文献
3.
V.G. Shevchenko I.N. Belskaya I.G. Slyusarev Yu.N. Krugly V.G. Chiorny N.M. Gaftonyuk Z. Donchev V. Ivanova M.A. Ibrahimov Sh.A. Ehgamberdiev I.E. Molotov 《Icarus》2012,217(1):202-208
CCD-photometry of three Jupiter Trojan asteroids were carried out to study their opposition effect. We obtained well-sampled magnitude–phase curves for (588) Achilles, (884) Priamus, and (1143) Odysseus in the maximal attainable phase angle range down to 0.1–0.2°. The magnitude–phase relations have a linear behavior in all observed range of phase angles and do not show any non-linear opposition brightening. We have not found any confident differences between phase slopes measured in B, V and R bands. The values of the measured phase slopes of Trojans are different from available data for Centaurs. They are within the range of phase slopes measured for some low-albedo main belt asteroids, also exhibit a linear behavior down to small phase angles. An absence of non-linear opposition brightening puts constraints on the surface properties of the studied objects, assuming very dark surfaces where single scattering plays dominating role.We also determined the rotation periods, amplitudes, the values of color indexes B–V and V–R, and the absolute magnitudes of these asteroids. 相似文献
4.
Eight eclipse reappearances of the innermost Galilean satellite, Io, were observed during the fall of 1973. The measurements were made using photometers specially designed to cope with the problem of scattered light from Jupiter. Posteclipse brightening of Io was not detected and, if present, was less than our estimated detection threshold of about 0.02 mag. 相似文献
5.
Four eclipse reappearances of Io were observed with an area-scanning photometer during the 1973 apparition of Jupiter. The results of these observations and of the ones reported in the preceding paper are discussed in the context of recent physical models for posteclipse brightening. An evaluation of the relative merits and deficiencies of all observational techniques which have been used to search for posteclipse brightening of Io leads to the conclusion that the reality of this phenomenon remains very much in doubt. 相似文献
6.
The Sun's gradual brightening will seriously compromise the Earth'sbiosphere within 109 years. If Earth's orbit migrates outward,however, the biosphere could remain intact over the entiremain-sequence lifetime of the Sun. In this paper, we explore thefeasibility of engineering such a migration over a long timeperiod. The basic mechanism uses gravitational assists to (in effect)transfer orbital energy from Jupiter to the Earth, and therebyenlarges the orbital radius of Earth. This transfer is accomplishedby a suitable intermediate body, either a Kuiper Belt object or a mainbelt asteroid. The object first encounters Earth during an inward passon its initial highly elliptical orbit of large ( 300 AU)semimajor axis. The encounter transfers energy from the object to theEarth in standard gravity-assist fashion by passing close to theleading limb of the planet. The resulting outbound trajectory of theobject must cross the orbit of Jupiter; with proper timing, theoutbound object encounters Jupiter and picks up the energy it lost toEarth. With small corrections to the trajectory, or additionalplanetary encounters (e.g., with Saturn), the object can repeat thisprocess over many encounters. To maintain its present flux of solarenergy, the Earth must experience roughly one encounter every 6000years (for an object mass of 1022 g). We develop the details ofthis scheme and discuss its ramifications. 相似文献
7.
Nurmi P. Valtonen M. J. Zheng J. Q. Mikkola S. Rickman H. 《Earth, Moon, and Planets》1997,77(3):239-244
We have developed an efficient Monte Carlo method by which we can evaluate the evolution of comets. There are many poorly
known evolutional parameters, and we have investigated the influence of these parameters on the final populations and the
inclination distributions of short-period comets. We compare the observed and calculated inclination distributions of different
comet populations and obtain a good fit for the inclinations of the Jupiter family comets by assuming a mantle blow-off and
a sudden brightening of the comet when its perihelion distance is lowered in a major jump.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
8.
Liu Jin-Yi 《Chinese Astronomy and Astrophysics》1984,8(4):354-356
For a given planet there is a critical distance from the Sun when the planet is first or last seen. This is called Jian-Fu-Du (JFD) by ancient Chinese astronomers. TABLE 1 lists the values of JFD for the five planets as given in 33 Chinese calendars between −103 and +1368. The data show that 1) in order of decreasing brightness, we have Venus, Jupiter, Saturn and Mars, while the brightness of Mercury is the same as the last two; 2) the JFD of Jupiter is decreasing in time; and 3) the JFDs of the other four planets are increasing in time. Perhaps changes in the transparency of the Earth's atmosphere and in the brightness of the Sun cause a general increase in JFD. Then the decreasing JFD of Jupiter means that Jupiter is getting brighter in time. A rough estimate for the rate of brightening is 0.003 mag per thousand years. 相似文献
9.
Maps of the Sun at 2.8 cm wavelength, observed with the 100-m telescope in Effelsberg, on 1972, October 31 and 1973, February 10, are discussed. The brightness distribution over the Sun is, with the exception of active regions, approximately constant and nearly sharp-edged. Regions of small enhancements in the radiation can be identified with zones of weak activity in the solar magnetograms. Optical filaments could also be seen in absorption at 2.8 cm wavelength, the optical depth being of the order of 0.2. Several active regions have been analysed with respect to their position relative to their optical counterparts and to their brightness temperature: The latter was found to reach almost 106K in one case. No noticeable limb brightening could be observed; if any exists, it should be smaller than 5%. Likewise no noticeable elliptical deformation of the Sun's disk could be found. The geometrical thickness of the coronal layer, contributing to the undisturbed radiation at 2.8 cm was estimated to be a maximum of 4000 km. 相似文献
10.
G.H. Rieke 《Icarus》1975,26(1):37-44
Infrared observations of Saturn from 5 to 40 μm are described. There is intense limb brightening at 12.35 μm over the southern polar cap. The C ring is anomalously bright at 10 and 20 μm and has bluer (hotter) colours than the A and B rings. The ring spectra have been extrapolated beyond 40 μm and subtracted from low-resolution far-infrared measurements to show that the far-infrared spectrum of the disk of Saturn is qualitatively similar to that of Jupiter and that Saturn radiates 2.5 ± 0.6 times the energy it absorbs from the Sun. 相似文献
11.
Since their discovery in Voyager images, the origin of the bright polar caps of Ganymede has intrigued investigators. Some models attributed the polar cap formation to thermal migration of water vapor to higher latitudes, while other models implicated plasma bombardment in brightening ice. Only with the arrival of Galileo at Jupiter was it apparent that Ganymede possesses a strong internal magnetic field, which blocks most of the plasma from bombarding the satellite's equatorial region while funneling plasma onto the polar regions. This discovery provides a plausible explanation for the polar caps as related to differences in plasma-induced brightening in the polar and the equatorial regions. In this context, we analyze global color and high resolution images of Ganymede obtained by Galileo, finding a very close correspondence between the observed polar cap boundary and the open/closed field lines boundary obtained from new modeling of the magnetic field environment. This establishes a clear link between plasma bombardment and polar cap brightening. High resolution images show that bright polar terrain is segregated into bright and dark patches, suggesting sputter-induced redistribution and subsequent cold trapping of water molecules. Minor differences between the location of the open/closed field lines boundary and the observed polar cap boundary may be due to interaction of Ganymede with Jupiter's magnetosphere, and our neglect of higher-order terms in modeling Ganymede's internal field. We postulate that leading-trailing brightness differences in Ganymede's low-latitude surface are due to enhanced plasma flux onto the leading hemisphere, rather than darkening of the trailing hemisphere. In contrast to Ganymede, the entire surface of Europa is bombarded by jovian plasma, suggesting that sputter-induced redistribution of water molecules is a viable means of brightening that satellite's surface. 相似文献
12.
Kumitomo Sakurai 《Planetary and Space Science》1976,24(7):661-664
Using the data obtained from the Pioneer 10 and 11 observations, a theoretical model is proposed for the bow shock and the magentosphere of Jupiter. This indicates that the distance of the magnetopause from Jupiter on the sunlit side is (50–55) × rJ (rJ: Jupiter radius, = 7 × 109 cm) and that the ratio of the stand-off distance to this distance is about equal to or slightly larger than unity. Hence the Mach number of the solar wind seems to be less than 1.5 at Jupiter's orbit. This result necessarily leads to a blunt body model of the Jovian magnetosphere, the tail region of which is not as extended as observed in the Earth's case. 相似文献
13.
The radio emission from Jupiter at 10, 21 cm wavelength has been measured with a spatial resolution of the order of 1 Jupiter radius. This may be analytically reduced to the emission per cubic centimeter of source at each measured frequency. The theoretically predicted synchrotron emission of electrons as a function of frequency, magnetic field and electron energy can then be compared to the observed source emissivity to obtain the number density and ‘temperature’ of the electrons. Present observations taken at different epochs are not sufficiently reliable to infer peak energies within an order of magnitude. Nevertheless the present results indicate that electrons diffuse in rapidly (in a time of the order of months) conserving the first adiabatic invariant and reach a peak energy at about 2 Jupiter radii. The electron energy decreases rapidly nearer the planet because of energy lost to radiation in the large magnetic field close to the planet. 相似文献
14.
two near-earth-asteroids associated with resonances with Jupiter are studied over a time span of 105 yrs. We found that asteroid (887) is temporary trapped in the 3:1 resonance; thus indicating that this resonance could be a source of short-lived NEAs. We also found that asteroid (3552) with a large eccentricity and a high inclination is wandering about the 1:1 resonant region. 相似文献
15.
F. MarchisI. de Pater A.G. DaviesH.G. Roe T. FuscoD.Le Mignant P. DescampsB.A. Macintosh R. Prangé 《Icarus》2002,160(1):124-131
Io, the innermost Galilean satellite of Jupiter, is a fascinating world. Data taken by Voyager and Galileo instruments have established that it is by far the most volcanic body in the Solar System and suggest that the nature of this volcanism could radically differ from volcanism on Earth. We report on near-IR observations taken in February 2001 from the Earth-based 10-m W. M. Keck II telescope using its adaptive optics system. After application of an appropriate deconvolution technique (MISTRAL), the resolution, ∼100 km on Io's disk, compares well with the best Galileo/NIMS resolution for global imaging and allows us for the first time to investigate the very nature of individual eruptions. On 19 February, we detected two volcanoes, Amirani and Tvashtar, with temperatures differing from the Galileo observations. On 20 February, we noticed a slight brightening near the Surt volcano. Two days later it had turned into an extremely bright volcanic outburst. The hot spot temperatures (>1400 K) are consistent with a basaltic eruption and, being lower limits, do not exclude an ultramafic eruption. These outburst data have been fitted with a silicate-cooling model, which indicates that this is a highly vigorous eruption with a highly dynamic emplacement mechanism, akin to fire-fountaining. Its integrated thermal output was close to the total estimated output of Io, making this the largest ionian thermal outburst yet witnessed. 相似文献
16.
E. A. Gurtovenko 《Solar physics》1967,1(3-4):389-396
A peculiar brightening was observed near the centre of the D2 line of Nai on July 28, 1966, in a position where no activity could be seen in the H line but where a new important active region formed during the next rotation of the sun. The brightening, first observed at 06:30 UT, progressively faded and disappeared before 07:10 UT. 相似文献
17.
Noriaki Watanabe 《Celestial Mechanics and Dynamical Astronomy》1992,54(1-3):279-286
According to some investigations (Lecar and Franklin, 1973; Franklin et al., 1989; Soper et al., 1990) asteroids cannot remain for along time between Jupiter and Saturn. But as it is well known there is a near 5:2 commensurability between Jupiter and Saturn. So there might be a possibility that asteroids between Jupiter and Saturn could be trapped in a resonant relation.In order to investigate this possibility, the changes of orbital elements of an asteroid whose initial value of semi-major axis corresponds to that of a 1:2 resonant orbit were investigated by means of a double precision Cowell method. The integration routine was kindly supplied by Dr Yoshikawa.We considered first a planar restricted problem of three bodies, Sun-Jupiter-Asteroid, then a four body problem, Sun-Jupiter-Asteroid-Saturn. When integrating the equations of motion, short periodic terms were not eliminated and in the second test the interactions between Jupiter and Saturn were retained. Whether a close approach occured or not was not investigated. In every case a
j = 5.20, a
s = 9.54 and a = 8.26 were adopted as initial values of the semi-major axis of Jupiter, Saturn and Asteroid respectively. 相似文献
18.
North to south scans of Jupiter at 7.8-μm wavelength in early 1981 confirm polar brightening events that correlate with LCMIII, such that a polar limb is bright when the corresponding magnetic pole is tilted eartward. The correlation with magnetic features of the planet suggests that the energy source for the brightenings is magnetospheric particles incident upon the polar regions of the atmosphere. The northern polar events are more prominent and more regular than the southern ones. The polar emission may be indirectly related to the ultraviolet absorber observed near the poles by Voyager 2. 相似文献
19.
We discuss the life-story of a transequatorial loop system which interconnected the newly born active region McMath 12474 with the old region 12472. The loop system was probably born through reconnection accomplished 1.5 to 5 days after the birth of 12474 and the loops were observed in soft X-rays for at least 1.5 days. Transient sharpenings of the interconnection and a striking brightening of the whole loop system for about 6 hr appear to be caused by magnetic field variations in the region 12474. A flare might have been related to the brightening, but only in an indirect way: the same emerging flux could have triggered the flare and at the same time strengthened the magnetic field at the foot-points of the loops. Electron temperature in the loop system, equal to 2.1 × 106 K in its quiet phase, increased to 3.1 × 106 K during the brightening. Electron density in the loop system was 1.3 × 109 cm–3 and it could be estimated to 7 × 108 cm–3 prior to the brightening. During the brightening the loops became twisted. There was no obvious effect whatsoever of the activity in 12474 upon the in erconnected old region. The final decay of the loop system reflected the decay of magnetic field in the region 12474. 相似文献
20.
We investigate the feasibility of using the Lense-Thirring effect to measure the rotational angular momentum of Jupiter and the Sun. This experiment uses gyroscopes in close Jovian and solar orbits. It is important because it provides direct, unique information. The angular momentum is not derivable from the gravitational moments when non-uniform rotation is present. Analysis shows that this experiment could be done around Jupiter with current technology, but could not be done around the Sun for some years.Supported in part, by a Dissertation Research Assistantship of the Graduate College, Iowa State University. 相似文献