Carlyle S. Beals, former Dominion Astronomer of Canada and one of the most distinguished astronomers Canada has produced, died on 2 July, 1979. Carl Beals was not only a great astronomer, known throughout the astronomical world for his studies of Wolf-Rayet stars and many other contributions to astronomy, but he was also a great human person who exercised considerable influence on the development of astronomy in Canada and elsewhere. I should like to dedicate this lecture to the memory of Carl Beals.

A general scheme of evolution of close binaries is outlined. Many types of observed systems are classified according to their evolutionary status. Present theory can account reasonably well for the mass transfer between the two components. There is no satisfactory theory of mass and angular momentum loss from binary (as well as single) stars. Most close binaries sooner or later should develop extended common envelopes. A loss of a common envelope may remove a large fraction of mass and most of angular momentum from a binary, and leave as a remnant a very short period and highly evolved system. Binary nuclei of planetary nebulae, cataclysmic variables and some X-ray binaries are produced this way.

I shall present here a picture of the evolution of close binary systems (CBS) as it is understood now. This is not intended to be a review, and no attempt has been made to make the list of references complete. Usually I shall refer the first paper on a given subject and/or one of the recent ones, where a large number of other references can be found. There are many reviews and proceedings of various symposia that deal with close binaries. Here are some: Annual Review of Astronomy and Astrophysics (9, 183, 14, 119, 15, 127, 16, 171, 241), IAU Symposia No. 73, 83, 88, IAU Colloquia No. 42, 46, 53. I shall try to emphasize what is known and what is not known, and how various observed systems fit into the theoretical evolutionary scheme. Because of my background I shall give more references to theoretical papers. Nevertheless, I am convinced that it was the theory of close binaries that was guided in its development by the observations, not other way around. In fact the theory predicted very few new phenomena and very few new types of binaries. But it managed to account, at least qualitatively, for the major evolutionary processes, and made it possible to arrange the observed systems into the evolutionary sequences.

My last attendance at a meeting of the International Astronomical Union was forty-four years ago when it met in Paris in 1935. I do not doubt that my being asked to give an invited discourse at this meeting is a personal courtesy extended to me by your distinguished President recalling, perhaps, the years when he and I were colleagues together at the University of Chicago.

I am aware that associated with my absence from these meetings for nearly half a century is the fact that during most of this period - if not all of it - my interests, at different times, have been outside whatever may have been the prevailing trends in the mainstream of astronomy. I am afraid that on this account, the point of view I shall present - retrospectively and prospectively - will not be in conformity with the trends currently prevailing. I must therefore begin by asking for your patience and for your forbearance.

Dr. Blaauw, when he invited me to give one of the three discourses at this meeting, suggested that in selecting a topic I might wish to take into account the fact that this year is the centennial of Einstein’s birth. The subject of my discourse is in accordance with that suggestion.

Many scientific justifications for space astronomy have been prepared by individuals and committees during the past three decades or more. The first such report that I am aware of, called “Astronomical Advantages of an Extraterrestrial Observatory”, was written by Lyman Spitzer in September 1946, and although its goals were extremely modest by today’s standards, the report did dwell with enthusiasm on the ultimate goal of a large reflecting telescope 4-6 meters in diameter with diffraction-limited optics put into earth-satellite orbit. The latest study, from which I shall quote liberally, has just been published by the Astronomy Committee of the U. S. National Academy of Sciences, and provides the scientific foundation for space astronomy in the 1980’s. Space Astronomy was initiated about one month after the date of publication of Spitzer’s report, when the first high-altitude rocket was launched to observe the sun’s ultraviolet radiation. Since that time, space astronomy has completed two phases and is about to embark on a third. In Phase 1, which lasted until the beginning of Sputnik, observations were made for a few minutes at a time from high-altitude rockets. In the second phase, which is just ending, observations were made with relatively small instruments in earth-orbiting satellites. The observing programs carried out with rockets and small satellites were called experiments because their capabilities and objectives were limited and their lifetimes were short -from a few minutes to about a year.

The topic of this Joint Discussion has received enormously increased interest in the last couple of years, owing to its potential for the investigation of the structure of the interior of the sun, including related topics like the structure of the convection zone, solar metal abundance, and the still unsettled neutrino problem.

The first stimuli came from the startling observations of Hill et al. (1976) in Arizona, Severny et al. (1976) on Crimea, and Brookes et al. (1976) in Birmingham, accompanied by a large volume of theoretical papers, the details of analysis of which soon went beyond the actual status of the observational facts.

We then witnessed, however, the success of considerable refinements of the techniques of observation, together with an obvious widespread temptation to push the interpretation of many of the new results to the limits of optimism. Yet, despite of the still increasing body of data suggesting the reality of the solar origin of the observed phenomena, much scepticism was prompted by the complicated statistics and the intricate numerical procedures involved in the data analysis, as well as by the great uncertainty about the significance and the amounts of “noise” contributed to the signal by electronics, changes of the conditions of the ray path within the telescope, terrestrial atmospheric inhomogeneities and solar quasi-stationary motions.

Continuous solar observations over extended periods of time with the sun at constant altitude have heretofore been unobtainable. A solar observatory at the geographic South Pole will provide continuous homogenous observations of various solar features during the austral summer months. An optical site testing campaign during January 1979 showed seeing conditions at the site to be even better than expected. During the 1979-80 austral summer solar global oscillations will be studied with the Nice sodium cell spectrophotometer. Lifetime studies of the chromospheric network will be conducted with a 30-cm heliostat in combination with a 20-cm f/100 objective lens to provide a 20-cm solar image for monochromatic filters during the following year.

A report published a decade ago by the U. S. National Academy of Sciences (1970) devoted one chapter to a discussion of the potential advantages of conducting certain types of astronomical observations at the geographic South Pole. One unique feature of this site is that it affords the opportunity for obtaining continuous homogenous observations with a single instrumental system over extended periods of time. Furthermore, special benefits for solar research stem from the constant angular level of the sun in the sky and the uniform local geography of the high altitude polar plateau (2912 meters, mean atmospheric pressure 680 mb corresponding to roughly 3300 meters at midlatitude).

There are several goals I hope to reach in this talk. First, I would like to give this broad audience some idea of our present state of knowledge concerning global circulation of the sun—what the observations tell us (and don’t tell us!) as well as current theories. This will comprise a large part of my talk. In doing this, I hope I do not bore the specialists in this area. Second, I would like to put the problem of global circulation of the sun in the broader context of “solar variability”, a topic of rapidly growing interest in the solar community, that has implications for stars generally, and which may not have caught the attention of the stellar community. I would like also to put the solar circulation problem in the context of stellar rotation, by making a few admittedly speculative extrapolations to other stars. In addition, I will give a few of my own opinions about what we should be doing in the near future to make more progress in understanding the solar problem. And finally, I hope to provoke a wide ranging discussion of the whole area of circulation and variability in the sun and stars.

One of the approaches for dealing with the differential rotation of the Sun is to separate the flow in the convection zone into an axisymmetric steady part (differential rotation plus meridional circulation) and a “turbulent” part comprising all smaller scales of motion. In the equations of motion and energy the effect of the small scales is then represented by a turbulent viscosity and conductivity. Theories of this type at present belong to either of two categories:

1. a) Theories stressing the role of an anisotropic turbulent viscosity. Due to the presence of gravity as a preferred direction the velocity distribution in the turbulent flow is different in the horizontal and vertical directions. This implies that the turbulent viscosity is also anisotropic. Biermann (1951) showed that as a result, the convection zone cannot rotate as a solid body. Theories based on this idea were developed by Kippenhahn (1963) and Köhler (1970).

2. b) Theories using a latitude dependence of the efficiency of turbulent transport of heat. In the deeper layers of the convection zone the influence of rotation on convection is strong because the convective turnover time is comparable to the rotation period. Since the angle between gravity and the rotation axis varies with latitude, this influence must also vary with latitude. This produces a temperature variation between the pole and the equator which drives a meridional circulation. Since the Coriolis force dominates over the viscous force in most of the convection zone, there is a strong differential rotation associated with this circulation (quasi geostrophic flow). This type of theory has been developed by Weiss (1965), Durney and Roxburgh (1971) and Belvedere and Paterno (1977).

The papers which follow here were given at the Joint Discussion on Nuclei of Normal Galaxies, held in Montreal on August 21, 1979, at the XVIIth General Assembly of the International Astronomical Union. This Joint Discussion was jointly sponsored by IAU Commission 28 on Galaxies, by Commission 33 on Structure and Dynamics of the Galactic System, by Commission 34 on Interstellar Matter and Planetary Nebulae, and by Commission 40 on Radio Astronomy. The scientific organizing committee consisted of W. B. Burton (Minnesota), chairman, R. D. Ekers (Groningen), H. Okuda (Kyoto), D. E. Osterbrock (Lick), V. I. Pronik (Crimea), and D. W. Weedman (Pennsylvania).

While preparing for this Joint Discussion, the organizing committee struggled with the problem of finding a suitable definition for the notorious word “normal” as applied to the enormously complicated phenomena of galaxies. What has become clear is that galactic nuclei of all sorts share an involvement in a continuous hierarchy. Thus the lower extent of the energy range exhibited by nuclei of Seyfert galaxies overlaps the upper extent of the energy range of galactic nuclei which most of us would classify as normal. Likewise, many agreeably-normal nuclei show signs of disruptive activity, high velocity dispersions, morphological asymmetries, and ejection. It has also become clear that study of nuclear phenomena must extend to include study of the entire bulge or core region. These matters are reflected in the papers which follow. These papers also collectively emphasize that galactic nuclei reveal different properties at different wave-lengths; presented at the Joint Discussion were results derived from optical and infrared data, as well as from millimeter and longer wavelength radio data. The papers also serve to put work on the nucleus of our own galaxy, which shows many of the same puzzling properties found in other normal galactic nuclei, into a pleasantly wider perspective.

Nuclei are often envisioned as sites for energetic and explosive phenomena in galaxies and may even be the birthplaces of quasars. Regardless of what models are chosen to represent such sources, a knowledge of the surrounding mass density and gravitational potential field is bound to be important for the creation and maintenance of the central engine. Moreover, galactic nuclei are worthy of close scrutiny even for their own sake. They constitute the brightest, most easily observed portions of galaxies and, in ellipticals, yield the central mass-to-light ratio, a quantity which cannot be determined for ellipticals using the ordinary rotation-curve method.

The radio properties of the nuclei of normal galaxies have been reviewed by Ekers (1974, 1978a, 1978b) and of the Galactic Centre by Oort (1977). In this report I will concentrate on material available since then. The following paper by Van der Hulst extends this review with more information on the structure of the central sources in normal galaxies.

No complete high resolution maps of Sgr A have been made since the “WORST” map (Ekers et al. 1975) so I will use it as a reference for the new information which is available. At the lower frequency of 327 MHz there have been a series of occultation measurements by Gopal-Krishna and Swarup (1976). These again show the separation into two components; a nonthermal Sgr A East and a thermal Sgr A West. In addition they show some spatial variation in the nonthermal spectral index and also suggest that the nonthermal source extends over the entire region of Sgr A. From observations using the RATAN telescope Parijskij (private communication) also suggests that the Sgr A East component might just be a peak on a more symmetrical nonthermal source which is centred on Sgr A West. RATAN observations are in progress in the wavelength range from 2-6 cm and these confirm the thermal nature of Sgr A West. As the VLA elements come into operation along more than one arm of the Y it becomes possible to use it to map Sgr A. 5 and 15 GHz maps (Brown, Lo and Johnston 1978 and private communication) with a resolution of a few seconds of arc resolve the Sgr A West source into a number of components with an overall size of ˜l’ × 30’ elongated along the galactic plane and centred on the Sgr A West point source (Balick and Brown 1974). The VLA maps of Sgr A West agree well with the inner contours of the WORST map and this distribution of emission is similar to that seen in the 53μ map (Harvey, Cambell and Hofmann’ 1976). Such an association is common in HII regions and is consistent with the thermal nature of Sgr A West.

It seems likely that we inhabit a galactic system which in its gross characteristics exemplifies the present meaning of the word “normal”. The general framework for interpreting the distribution and kinematics of the observed gas consists of a well-defined rotation curve, applicable over the great majority of a thin, nearly flat disk; the stars and gas within this disk are generally quite cold, having little energy in random as opposed to well-ordered motions. In fact, neutral gas in the galactic disk is sufficiently regular in its structure that no grand pattern of spiral arms stands out in sharp relief.

As one moves inward in the Galaxy from the location of the Sun, this regularity persists to within about 4 kpc of the center, at which distance the abundance of gas in either atomic or molecular form drops fairly abruptly. Inside this region, the character of the gas distribution undergoes a marked change and the behaviour observed there, while it may be common to even the best-ordered systems, represents a rather spectacular departure from the organization at larger galacto-centric radii. As the gas abundance increases once more toward the galactic center it is seen to reside in a multitude of individual features having disparate spatial and kinematic properties. Many of these have large and/or obvious components of non-circular motion, usually taken as indicating expulsion of matter from the galactic center region at both large and small angles with respect to the rotation axis of the galaxy at large. Others, while occurring at velocities whose sign is consistent with rotation motion alone, have contradictory changes in velocity with position. Line profiles taken in the inner regions of the Galaxy are generally decomposed according to catalogs of classifiable features but no generally accepted interpretative framework exists as a means of relating the wide variety of observable phenomena.

Infrared observations of the galactic nucleus and conclusions regarding the nature of the objects present there are reviewed. Observations of three sources of infrared radiation are discussed: near-infrared emission from cool stars, mid- and far-infrared emission from dust, and line emission from ionized gas. These observations provide information about the mass distribution, the stellar population, and the origin and ionization of the compact mid-infrared sources. The possibility of the existence of a massive central black hole is discussed.

Molecular hydrogen of ≥108M⊚ exists in the galactic center region as has been revealed by recent observations of molecular emission lines. In the inner region of , most of the dominant emission features are located at and 0 km s-1 ≤ v ≤ 100 km s-1 extremely unevenly with respect to the galactic center. As a model of the molecular complex we propose a fan of 360 pc radius whose pivot is at the nucleus. The vertical angle of the fan is about 50° and the central line of the fan makes an angle of about 60° to the line of sight. Molecules in the fan are radially outflowing from the center with the velocity of 110-140 km s-1l. The 1-v pattern of the fan model agrees very well with the observational data. As for Sgr A and Sgr B2 numerical calculation of molecular line profiles has been made by using the large velocity gradient approximation. The calculation shows that the broad and asymmetric line profiles in the complex are well reproduced in the fan model. Further, an isotope effect on line shape is predicted, which will be viable for an observational check of the model.

At the present time we do not know with any certainty what the infrared properties of “normal” galaxies are, although we do know that substantial broad-band emission at 10μm is fairly common in spiral galaxies; Rieke and Lebofsky (1978), for example, were able to detect the nuclei of 16 out of 39 bright spiral galaxies above a level of about 50 mJy. Only one of these, NGC 1068, is a Seyfert Galaxy.

With the exception of M31, whose 10μm emission can be accounted for entirely by stellar photospheric emission, all the spiral galaxies detected in Rieke and Lebofsky’s survey show strong emission from heated dust grains. Airborne observations at longer wavelengths (e.g., Telesco and Harper 1980) of a few of these galaxies show a peak in the energy distribution at around 80μm, corresponding to dust temperatures of order 30-60K, while spatial scans, and multi-aperture photometry at 10μm (Rieke 1976; Becklin, Fomalont, and Neugebauer 1973; Becklin et al. 1980) indicate a physical size for the emitting region of a few hundred parsecs diameter.

During the last few years detailed and sensitive observations of the radio emission from the nuclei of many normal spiral galaxies has become available. Observations from the Very Large Array (VLA) of the National Radio Astronomy Observatory (NRAO1), in particular, enable us to distinguish details on a scale of ≤100 pc for galaxies at distances less than 21 Mpc. The best studied nucleus, however, still is the center of our own Galaxy (see Oort 1977 and references therein). Its radio structure is complex. It consists of an extended non-thermal component 200 × 70 pc in size, with embedded therein several giant HII regions and the central source Sgr A (˜9 pc in size). Sgr A itself consists of a thermal source, Sgr A West, located at the center of the Galaxy, and a weaker, non-thermal source, Sgr A East. Sgr A West moreover contains a weak, extremely compact (≤10 AU) source. The radio morphology of several other galactic nuclei is quite similar to that of the Galactic Center, as will be discussed in section 2. Recent reviews of the radio properties of the nuclei of normal galaxies have been given by Ekers (1978a,b) and De Bruyn (1978). The latter author, however, concentrates on galaxies with either active nuclei or an unusual radio morphology. In this paper I will describe recent results from the Westerbork Synthesis Radio Telescope (WSRT, Hummel 1979), the NRAO 3-element interferometer (Carlson, 1977; Condon and Dressel 1978), and the VLA (Heckman et al., 1979; Van der Hulst et al., 1979). I will discuss the nuclear radio morphology in section 2, the luminosities in section 3, and the spectra in section 4. In section 5 I will briefly comment upon the possible implications for the physical processes in the nuclei that are responsible for the radio emission.

The principal motivation behind the work summarized below was to define the nature of a “typical” galactic nucleus and thereby determine whether such nuclei differ from active nuclei in a qualitative or only quantitative sense. I hoped that such a study would then yield clues as to the origin and duration of nuclear activity and the effects such activity might have on the structure and evolution of the surrounding galaxy. For a more complete discussion of the results below, see my Ph. D. dissertation (Heckman, 1978) or the series of three papers (Heckman, 1979) to be published elsewhere.

For a sample of 21 Sc galaxies with a wide range of luminosities, of radii, and of masses, W. K. Ford and I have obtained spectra and determined rotation curves. By their kinematical behavior in their central regions, the Sc’s can be separated into two groups. Some galaxies, generally small and of low luminosity, have shallow central velocity gradients, reflecting their low central masses and densities. Other galaxies, most often large ones of high luminosity, have steep central velocity gradients. One reason this separation by central velocity gradients is of interest is because these galaxies exhibit other significant spectral differences which go hand-in-hand with the kinematical differences.

The small, low luminosity galaxies show emission lines of Hα and [NII], with nuclear Ha sharp and stronger than [NII], and little or no stellar nuclear continuum, just as conventional HII regions. In contrast, the high luminosity galaxies show broad nuclear emission, with [NII] stronger than Ha. These galaxies have a strong red stellar continuum, arising from a red stellar population. The cause of the Hα[NII] intensity reversal in the nuclei of some galaxies remains unknown. However, the strong [NII] emission in generally high luminosity galaxies with massive nuclei, nuclei which show strong red continua, suggests that [Nil] intensity correlates with nuclear luminosity, and in turn with the density and velocity properties of the nuclear populations. We would expect high velocity dispersions and high bulge luminosities for galaxies with strong nuclear [NII] and steep central velocity gradients.

Early type galaxies classified as SO by Sandage or lenticulars and SO/a appearing in RCBG have been observed with the IDS on the ESO 3.6 m telescope. The slit was 1” × 4” and the spectral resolution was 9 Å from 3900 Å to 7000 Å. Statistics for the first 50 galaxies observed are given.

18% of the sample show the [OIII] doublet stronger than Hß; 32% have spectra dominated by the Balmer series progressing from mainly emission through strong absorption series to weak absorption; 20% have only [NII] or [SII] in emission while 30% show absorption lines and bands. That is, 70% show emission lines toward the nuclear region. Among the 50 galaxies, HI at 21 cm has been detected in 21 galaxies: 16 of these show ionized gas to be present. NGC5273 has Seyfert characteristics with strong [OIII]; Hß has a width of ˜1000 kms-1. The low luminosity end of the Seyfert distribution may be found among normal galaxies.