We present an hitherto unknown cometary reflection nebula {a = 20^h18^m3, δ+37°00') associated with a dense dust cloud. A bright, compact Herbig-Haro oject is embedded in its brightest part. The highly reddened illuminating star of about 3-5 M„, located near the apex of the nebula, emits a collimated bipolar flow at high velocity, whose blueshifted stream feeds the HH object. The redshifted stream can be traced toward the interior of the dark cloud, where the density exceeds 10^5 cm^-3.
A method of reduction of dimensionality in discriminant analysis has been specially designed for this study of separation between two populations and it is only based on the heterocedasticity
of both groups. For this reason, it is of interest in the case of zero mean difference vector. Two examples of application, concerning the membership problem in open clusters from uvby and
Hβ photometry and the separation of globular clusters into Oosterhoff's groups are shown.
In recent papers Henrard and Lemaître have studied what they call "The Second Fundamental Model for Resonance" and higher order generalizations of it. The action integral ("area index") was computed analytically, but the phase space and the action integral as a function of the parameter δ were only plotted on scale by a computer. By using properties of quartic equations, however, the mathematically special values of δ were found. For third order resonances, one of these turned out to correspond to a minimum
in the value of the "area index" A2, but since it is very shallow and very close to the starting point of the function, this feature was invisible in Lemaître's plots, This has some theoretical implications for the process of capture into a third order resonance, although numerically the effect will be small due to the shallowness of the minimum. A similar exercise on first and second order resonances revealed no new features.
Many recent observations have shown that resonances have a wide variety of effects in planetary rings: spiral waves, gaps, confinement, sharp edges, arcs. While resonances are known to be associated with such structures, the role of inter-particle collisions is still poorly understood, although necessary to explain the long term evolution of the rings.
In an effort to better understand the associated dynamics, we have performed numerical simulations of colliding particles orbiting a massive central planet. The code simulates the 3-D motion of 100 identical spherical particles orbiting a massive cental body and suffering inelastic collisions while being perturbed by one or more satellites.
We used this code to explore in more details the dynamics of are rings, and to explain in particular the reeent observations of are structures around Neptune. Clusters of particles at a satellite’s Lagrangian point {L4 or L5) are shown to be dispersed by dissipative effects. However, a second satellite can stabilize the system by providing sufficient energy through a Lindblaďs
resonance m±l:m. Other dynamically equivalent configurations (e.g. only one satellite, but with an eccentric orbit) can also stabilize are sytems, in accord with current analytical models.
We examine the roles of collisions at Lindblad and corotation resonances in various cases. Arcs remain at the potential maxima created by the corotations. However, stability requires that the satellites’ masses be within a limited range: small satellites cannot provide enough energy while large ones give too much, so the arc can disperse.
We have computed the following physical parameters for the atmosphere of Titan, usinge Voyager´s measurements:
1) Temperature, 2) Pressure, 3) Density, 4 Speed of sound, 5) Density scale, 6) Number density, 7) Mean free path, 8) Viscosity, 9) Pressure scale, 10) Mean particle velocity, 11) Mean collisional frequency, 12) Columnar mass.
The spatial distribution of the young objects of varioue age groups -
HII regions and open clusters - in the Saglttarius-Carina arm (SC arm) at 1 « 280°- 25° ie Inyestlgated. Both transverse and longitudinal age gradients have been found in the arm, Two giant star formation complexes with the size of about 1 kpc at 1 = 285°-300° at 1 = 340°-20° are existed, Each of them contains several giant HII regions, a number of glant moleoular clouds (GMCa) and some extremely young clusters, Between these complexes we have found an elder one of the same aime.This complex contains 24 (3-6)»10^7 years old clusters and a small number of faint HII regions. Assuming that it is a remnant of a
giant star formation complex the upper limit of lifetimes for such complexes and GMCs is (3-6)•10^7 years,
The estimations of spiral pattem parameters are made.The value of the pitch-angle is 21°+3°. The value of spiral pattem velocity, -26.8+2.2 km/s«kpc, leads us to conclusion that the Sun is near the oorrotation radius of the Galaxy. The star formation efficiency in
these complexes is discussed.
The modern generation of electronic detectors, such as the CCD, have made improved photometry possible, especially at magnitudes near photographic plate limits and at wavelengths extending to the near infrared. Vigorous efforts should now be made to extend measurements to longer wavelengths since VandenBerg and Bell (1985) have recently calculated BVRI synthetic isochrones. Consequently, we have embarked on a program of CCD BVRI photometry for determining the ages of globular clusters.
From BVRI CCD frames obtained with the 1.54 Danish telescope at ESO-La Silla we have at this moment completed the reductions of the following 5 globular clusters: NGC 104 (47 Tuc), NGC 2298, NGC 5139 ( 0) Cen), NGC 6121 (M4), and NGC 6362. For these clusters, we have derived ages all close to 17x10^0y. Providing strong evidence that the globular cluster system is coeval, and that the epoch of the galactic contraction was short.
Vysněného cíle nakonec dosáhlo šest výprav. Dvě posádky testovaly mateřskou loď i lunární modul na oběžné dráze Země, jiné dvě na oběžné dráze Měsíce. Apollo 13 zažilo nejúspěšnější neúspěch. Dvanáct lidí - výpravy Apollo 11, 12, 14, 15, 16 a 17 - na povrchu Měsíce chodilo, skákalo, padalo, jezdilo i tak trochu bouralo. Zpět na Zemi přivezli kosmonauti na čtyři sta kilogramů hornin. Jimi prováděné experimenty, z nichž jeden stále běží, si vzaly na paškál studium mechanických vlastností půdy, měsícotřesení, vlastností slunečního větru... Jedinou vadou na kráse je, že se tak stalo už před padesáti roky. and Jiří Dušek.
This contribution presents a review of resonance phenomena associated with the orbital motion of artificial satellites. Following an outline of the principal features of satellite motion and tracking
methods the topic of passage through high-order resonances is discussed. Next, a brief description of geostationary and other
low-order resonant orbits is presented. The paper is concluded with an historie account of the well-known critical inclination problem.
International Workshop on Astronomical X-Ray-Optics (AXRO) organized by the Institute of Astronomy of the CAS was focused on presentation and discussion of recent and future technologies for future X-ray astronomy missions. One session was aimed on astrophysical aspects of X-ray telescopes/satellites, in which some review talks were given from leading scientists in this field plus some presentations of relevant Czech scientists. The goal of the workshop was to present and to discuss recent and future technologies for X-ray astronomy missions. These missions require development of mostly inovative technologies, and discussed the possibilities, the results obtained so farm and new ideas in detail. It is obvious that the requirements of future large space X-ray optics based on Si wafers, advanced glass forming for precise X-ray optics, but also other possible technologies and alternatives, as well as related advanced metrology, measurements and tests. and Martin Blažek.