Preliminary results are presented of an intensive multifrequency observing campaign on SS 433 conducted in 1987. There were participants from all over the world; they brought all the observations together at the 1988 Dwingeloo workshop on SS 433. With a rapid sequence of VLBI maps, we have been able to follow the onset and evolution of a series of radio flares. We have also obtained a wealth of optical spectra allowing studies of the variability of the Doppler shifted lines on timescales of hours. There is little correlation between the activity in the radio regime, and that seen in the Doppler shifted lines.

The physics of large scale jets in class I and class II extragalactic radio sources and quasars is discussed. Class I jets appear to be turbulent, transonic jets which entrain the interstellar medium. The related jet deceleration causes a slow surface brightness decline which is usually observed. Class II jets are supersonic and terminate in an advancing shock against the external medium. Both types of jet are initially light but the ratio of jet density to external density of class I jets increases owing to entrainment. It is quite plausible that quasar jets are hypersonic and light and this may solve problems of confinement. The velocities of class I jets are of the order of a few thousand kilometers per second. Class II and quasar jets may be at least mildly relativistic. However, it is not clear whether the velocities of large scale jets in powerful sources are close to the speed of light. Recent depolarization measurements provide an interesting focus for discussion of this question.

Recent VLA observations of the lobes of Cygnus A exhibit complex “filamentary” structures, with typical scale width ~ 1 arcsec (Dreher, Carilli and Perley, 1987, Perley, 1987). The filaments appear aligned with the magnetic field, as results from polarization measures, suggesting that the field may play a fundamental role in the process of their formation.

We propose a mechanism for the possible formation of these filaments based upon a thermal instability connected with synchrotron emission from relativistic electrons. This type of instability was studied by Simon and Axford (1967), who discussed it in connection with the Crab Nebula filaments, and by Eilek and Caroff (1979), who generalized the previous study for application to quasar atmospheres.

The basic question I want to address is : “What mechanism or mechanisms accelerate the gas in the narrow line region of active galaxies, yielding the observed profile shapes.” At the present time there is no generally accepted answer to this question. Part of the problem dates back to the first few Seyferts that were discovered which, in retrospect, seem to have had anomalously broad lines. For example NGC 1068, MKN 3, and MKN 78 have [OIII] λ 5007 FWHM ~ 1000 km s-1, which is clearly greater than anything associated with a normal galaxy velocity fields. An obvious implication was that these high velocities were in some way related to the activity. This view was reinforced by the discovery of a correlation between [OIII] FWHM and non-thermal radio luminosity (Wilson and Willis 1981). When many radio sources were found to have linear double or triple morphology (e.g. Ulvestad and Wilson 1984a,b), a natural explanation seemed to be outflowing radio jets which stir up the narrow line region and thus generate the correlation between line width and radio luminosity.

Different models of extragalactic jet formation have been proposed in the litterature. They usually considered only one population of particles, ascribing one typical bulk velocity to the jet. However from the point of view of plasma physics it seems very likely that beams of particles with different velocity will be generated in the surroundings of the central engine by any kind of jet acceleration mechanism. This can lead to a typical beam-plasma configuration with a slow ambient plasma pervaded by energetic beams which constitute a population inversion and are a potential source of energy and of instability.

Highlights of the science program to be carried out by the Hubble Space Telescope are reviewed. Some of the main scientific projects to be carried out by the General Observers (GOs) and the Guaranteed Time Observers (GTOs) during the early phases of the Space Telescope are discussed. The method and criteria for selecting science projects are also discussed.

The Hubble Space Telescope Second Generation Instrument Program is described. The original instrument selection process in 1985 is discussed as well as the NASA plan to make a final selection of an infrared instrument in late 1988.

The Wide Field / Planetary Camera-II will be available to replace the WF/PC at the first opportunity for in-orbit Shuttle maintenance and refurbishment of the Hubble Space Telescope. It is fundamentally an engineering “clone” of the original radial camera, which nevertheless incorporates a number of science and operational enhancements based on improved technologies. Generic WF/PC performance issues identified and understood early in the WF/PC-II program provide the opportunity for carefully considered, cost effective hardware refinements. The result is improved science performance and operational efficiency for WF/PC-II which will be highly visible to the GO astronomer, and will provide savings in data reduction and calibration overhead.

Biased-platinum-gate CCD technology is introduced for the eight imaging sensors, in order to provide long and short term QE stability while obviating the solar UV light channel. Signal chain electronics have been modified in several ways to improve science performance and operational efficiency. The WF/PC set of 48 filters has been reviewed and a number of modifications have been implemented. The WF/PC-II is well into construction at JPL, scheduled for delivery in late 1991.

The Space Telescope Imaging Spectrograph (STIS) is a second generation instrument to be installed into the Hubble Space Telescope (HST) in-orbit 5–9 years after the first launch. Together with the infra-red instrument, it will provide a large increase in capability of the observatory, and be able to replace a first generation that had failed or degraded.

The Hubble Space Telescope is to be a long-lived observatory with wide-ranging spectroscopic and imaging capability in the UV and the visible, and in the near-IR as the second-generation instruments are implemented. HST will have a dramatic impact on our view of the universe. However, it is by no means premature to address the issue of its successor, even though HST has not yet been launched. We must look ahead with the realistic view that HST will degrade and will need to be replaced. The question that we must then address is:

What is the UV-Visible-IR Observatory that will follow HST?

I will make the case for this being an 8-16 m class telescope.

I have a strong feeling that I am not the right person to give this lecture. Many of you will have noticed that recently the National Academy of Sciences has published a report entitled “Space Science in the 21st Century – Imperatives for the Decades 1995 – 2015”. This assessment was requested by NASA and was headed by the Space Science Board of the National Academy of Sciences. This is a very large and ambitious report and is essential reading for those who wish to have a broad vision of what might become possible in the coming decades. As a result, this brief review will make no attempt to be complete but will simply raise some points which may contribute to the discussion of future directions of space astronomy. I would emphasise that these are personal views.

The accuracies being achieved in astrometry, celestial mechanics, Earth Orientation, ephemerides and time have been improving significantly in recent years.

The introduction of the improved astronomical constants, ephemerides, time scales and nutation as adopted from 1976 to 1984 has had the desired effect of permitting the investigation of systematic effects at precisions of an order of magnitude better than previously possible.

Therefore, there have been many developments in observational data, in theories, and in astronomical computations that have promised, or claimed, to deliver accuracies of a milliarcsecond or better.

Working Groups had been established with interrelationships in their scopes of activities. It did not appear that any of the working groups were prepared to present final recommendations that would be generally accepted.

Gordon Allen Newkirk, Jr. was born in West Orange, New Jersey June 12, 1928 and died in Boulder, Colorado December 21, 1985 at age 57. He was graduated from Harvard University in 1950 and in 1953 earned a Ph.D. in astrophysics from the University of Michigan. In 1955, after service in the Signal Corps of the U.S. Army he took a position at the High Altitude Observatory in 3oulder where he worked the remaining thirty years of his life. For 11 of those years (1968-1979) he was director of the observatory and associate director of the National Center for Atmospheric Research. He was also active as a teacher and from 1965 through 1985 was an adjoint professor at the University of Colorado. From 1972 through 1975 he served as Chairman of the Solar Physics Division of the American Astronomical Society and from 1976 through 1979 as President of Commission 10 (Solar Activity) of the International Astronomical Union.

Our recent understanding of the structure of the solar corona is reviewed, with an emphasis on the ground-based observations.

After four decades of study, the mechanisms for heating the corona are not understood. However, the development of the field is vigorous. A variety of new ideas have been proposed, and these new ideas have generated lively debate. The goal of this short review is to present a broad overview of the ideas currently under consideration.

It is now accepted that the solar magnetic field is the key ingredient. It is not known whether waves are important or not, but it is agreed that the magnetic (and possibly associated kinetic) energy must eventually appear in thin structures so that the (generally weak) dissipative processes can heat the plasma. This poses a problem of how the heat gets distributed throughout the corona.

With the closing of the Einstein and EXOSAT eras, the characteristics of stellar x-ray emission are now fairly well understood. In this very brief review, I will focus on two specific topics central to the physics underlying stellar activity: the rotation-activity connection and the “decay” of activity at the low mass end of the main sequence.

This review discusses winds from stars with hot outer atmospheres, stars with coronae similar to the sun. It illustrates how solar observations can be used to test a theoretical model for solar-stellar winds, and thereby provide some insights concerning applications to studying winds from stars other than the sun.

The interest in the stability of coronal structures derives from their observed lifetime (much longer than the relevant hydromagnetic timescale) coupled with their active behavior. This fact implies that these structures must be globally stable with respect to fast and destructive instabilities and, at the same time, must allow some local, non-disrupting, dissipative process to take place. In highly magnetized media as solar and stellar coronae a large number of plasma instabilities can occur. The present review will concentrate on those governed by the magnetohydrodynamic (MHD) equations with the inclusion of the effects of finite resistivity and viscosity and the use of an energy equation where radiation, mechanical heating and thermal conduction are considered.

Accretion disk coronae around compact objects are the result of strong magnetic activity in the inner regions of accretion disks. Part of the accreting energy is dissipated in te corona and can be observed as hard X-ray emission with a time variability caused by the coronal structures. The interaction of disk coronae with neutron stars and black holes may cause quaslperiodlc oscillations respectively flare type emission.

This review concentrates on some selected topics concerning the release of magnetic energy and associated phenomena in flares. Emphasis is on microflares, recent studies of different phases of flares, and propagation and trapping of flare accelerated electrons. The ongoing analysis of the observations of the previous solar cycle reaches a state where quantitative models become possible. The subject of solar flares can be broken up into several, now well defined physical problems.