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It has been clear for many years that the bulk of the chemical elements making up the solar system and the stars in our Galaxy were not formed in a single event of nucleosynthesis but were generated in a variety of different processes (Burbidge, Burbidge, Fowler, and Hoyle, 1957 hereinafter referred to as B2FH). Only the helium could have been synthesized in a big bang, if such a cosmological event occurred, and the present evidence suggests that the bulk of the Galactic helium was not synthesized in this way (Burbidge, 1969). Thus, it appears that the elements were synthesized in a variety of normal stars at different stages in their evolution, and also probably in more massive stars which may have been present at some epoch. If the composition of our Galaxy is explained in this way, it might be reasonable to assume that a particular set of processes occurred which are unique to our Galaxy, and that therefore its element abundance curve is different from that of all other galaxies. A test of this hypothesis would be to investigate the chemical compositions of other galaxies which have not gone through the same evolutionary processes. The nearest galaxies, and thus those which are easiest to study, are the Magellanic Clouds.

The observation of close pairs of QSOs with very different redshifts has been suggested by some as evidence in support of the noncosmological redshift hypothesis. A method is described for determining the statistical significance of such pairs. As an example, it is shown that the statistical significance of the pair 1548+115a,b is not well defined and ranges from approximately 99% confidence to about 60%. If statistical methods are to be used in such cases, they must not be argued a posteriori.

NGC 5128 is a peculiar galaxy which is of great interest, especially because it is at the centre of a very strong and exceedingly large source of radio emission known as Centaurus A1. The galaxy has been illustrated in the plate published by Baade and Minkowski2 and also in the Hubble Atlas3. It consists of a very bright elliptical galaxy classified EO with a very wide dust lane crossing it and roughly dividing the bright area of luminosity in half. Baade and Minkowski interpreted the structure as being due to a collision between an elliptical galaxy and a smaller spiral system. At that time the only spectra available were those of Hubble4 and Humason2. Neither gave sufficient information from which the true nature of the object could be deduced from the motions of the gas and stars in it, and the collision hypothesis based on interpretation of the direct plates alone has been a subject of controversy.

Inverse Compton effect in models of quasi-stellar objects demonstrated to be independent of magnetic field

The bursts of radio waves at decametric wavelengths emitted by Jupiter suggest a model for producing the signals from the pulsating radio sources. This mechanism includes polarization of the signals and structure within the pulses.

Red shifts of quasi-stellar objects and relation to radio and optical magnitudes, concluding that red shifts have no relation to distance

Condensed supernova remnants in Crab Nebula, considering various hypotheses for radio source

IT appears that we are now in agreement that star formation in the central regions of elliptical galaxies under the conditions originally postulated by Dr. Cameron is highly improbable. Cameron still believes that such processes may go on outside the nuclear regions of such galaxies. To this I would offer the following brief comments

CAMERON1 considers that the mechanism which I have proposed to explain radio emission from elliptical galaxies2 is implausible. Since I have been looking into this question rather carefully, I do not agree; but the discussion of this problem is of great complexity and nothing can be gained by making general assertions. Let us concentrate therefore on a discussion of the mechanism of energy generation put forward in Cameron's communication with the view of deciding whether it provides a reasonable alternative to the mechanism proposed by me.

A comparison of the cataloged coordinates of QSOs and of 3CR galaxies with those of Abell's rich clusters of galaxies yields the following results: (1) There is no statistically significant evidence that high-redshift QSOs lie preferentially close to Abell clusters. (2) There is no statistically significant evidence that low-redshift QSOs lie preferentially close to Abell clusters. (3) There is (as is well known) highly significant evidence that 3CR galaxies lie preferentially close to Abell clusters. (4) The distributions of angular separations between QSOs and clusters and between 3CR galaxies and clusters differ at statistically significant (but not highly significant) levels. In view of these results, a generic relationship between low-redshift QSOs and radio galaxies seems questionable. This result for the QSOs is also entirely consistent with the idea that they are 'local' objects with redshifts of noncosmological origin.

Following the earlier work of Wagoner (1967) we have reexamined the possibility that the absorption spectra of QSOs are due to gas in the disks, coronae, or halos of intervening galaxies. Comparison of the expected number of absorption systems with the number observed in all of the QSOs and BL Lacertae objects so far cataloged shows that there is a gross discrepancy in the sense that the multiplicity of absorption systems already found is far higher than the numbers expected if the absorption is due to gas in known disks or hypothetical small coronae. A discussion of the selection effects suggests that the number of absorption systems so far reported is an underestimate, so that an even greater discrepancy is likely to be present. High multiplicities can be explained only if very large halos or clouds containing heavy elements are commonly present, and there is no independent evidence for this. We conclude that the bulk of the absorption is likely to be intrinsic to the QSOs.

High-resolution spectrograms of six QSOs with apparent visual magnitudes of 17.0 to 18.5 and redshifts greater than 2 are studied for absorption lines. Accurate wavelengths are measured for all the absorption lines that could be detected, attempts are made to identify redshift systems, and the redshifts in each object are examined. Analysis of the absorption-line spectra shows that: (1) a large number of redshifts covering a wide range of values are present in five of the QSOs; (2) about two-thirds of the absorption lines remain unidentified, cannot be of Galactic origin, and are not associated with existing redshift systems; (3) many comparatively small absorption redshifts exist which, if they are due to intervening galaxies, must be produced by very large halos; and (4) in one QSO there is a possible redshift system containing five lines with an absorption redshift that is significantly greater than the emission redshift.

Spectrograms of the radio galaxy identified with the source DA 240, obtained with the Kitt Peak 4-m telescope and Ritchey-Chretien spectrograph, reveal the presence of ionized gas in the jet discovered earlier. This gas has a large negative velocity displacement of 3400 km/s relative to the center of the galaxy. This is further evidence for the ejection of gas in a violent event in the nucleus of a radio galaxy. The velocity gradient in this gas is less than about 50 km/s over 14 kpc.

A catalog containing basic optical information on all radio galaxies (radio luminosity at least about 10 to the 41st erg/s) which have been identified and for which redshifts have been measured is given. Included are the coordinate designations; other names; equatorial coordinates; visual magnitudes; galaxy types; redshifts and the lines on which they are based; radio flux at 408 MHz where it is available; radio spectral index; and references for identification, finding charts, and optical and spectroscopic studies. Cross-reference tables are provided for finding coordinate designations of sources known by noncoordinate names.

The paper contains a catalog of all known quasi-stellar objects with measured emission redshifts, and BL Lac objects, complete to September 1986. The catalog contains 3681 objects, comprising 3594 QSOs and 87 BL Lac objects. The catalog and references contain extensive information on names, positions, magnitudes, colors, emission-line redshifts, absorption, variability, polarization, and X-ray, radio, and infrared data. A key in the form of subsidiary tables enables the reader to relate the name of a given object to its coordinate name, which is used throughout the compilation. Plots of the distribution on the sky, the Hubble diagram, the apparent magnitude distribution, and the emission redshift distribution are also given. 1775 references.

This book presents papers on astronomy and astrophysics. Some of the topics covered include the physics of supernova explosions; mass loss from cool stars; global structure of magnetic fields in spiral galaxies; pulsar timing and general relativity; and star counts and galactic structure.

It is proposed that most of the very high-luminosity IRAS galaxies, those which emit greater than or equal to 10 to the 12th solar luminosities nearly all in the far infrared out to 100 microns, are very young systems with ages less than or equal to 10 to the 9th years. The luminosity comes largely from stars with masses near 100 solar masses which evolve rapidly, ejecting much of their mass as elements heavier than hydrogen. The gas ejected condenses into dust in circumstellar shells. The prototype star in the Galaxy which shows all of these attributes is Eta Car. It is shown that total masses of order 10 to the 7th-10 to the 8th solar masses condensed into such stars can produce the observed luminosities, and that 10-100 generations of such stars will produce enough dust (about 10 to the 8th solar masses) to explain the observed infrared luminosities. If this hypothesis is correct the composition of gas and dust may well be highly anomalous, and there should be no old stars with ages about 10 to the 10th years present. Initial star formation is probably triggered by interactions with close companion galaxies.

Liste de tous les quasars (708) ayant ete decrits dans la litterature depuis septembre 1986, date de parution du «New Catalog of QSOs» de Hewitt et Burbidge (1987)

Empirical spectroscopic evidence is examined for the hypothesis that radiation pressure having large gradients with wavelength plays a crucial role in maintaining patterns of redshift differences in quasars. Seventy-four absorption-line redshift systems in 32 quasars and two Seyfert galaxies are analyzed and discussed in terms of the radiation-pressure line-locking hypothesis. Redshift line ratios greater than unity are computed for each quasar and plotted as histograms. Ratios which may indicate line and edge locking are identified, including those of the C IV and Mg II doublets and those of the N III/C III, He II/O III, C II/He I, Ly-beta/H I, and H I/He I ionization edges.

The galaxy MCG 9-13-66 associated with the large radio source DA 240 has been shown to contain a large jet with a featureless spectrum somewhat bluer in color than the galaxy, oriented at 62degree to the axis of radio emission. Observations made at Kitt Peak National Observatory and Lick Observatory are described.

A critical analysis of the observations made by Einasto et al. and Ostriker et al. (1974) regarding the masses of galaxies is presented. The criticism centers on the assumption of gravitational binding in calculating the masses. Suppositions regarding halos surrounding galaxies; noncircular motions in outer spirals; physical bindings between our Galaxy and the six dwarf elliptical galaxies near it; and the masses of double galaxies and clusters are analyzed, and it is concluded that there is no independent observational evidence that the masses in these cases are very much larger than those derived in the investigation of single galaxies. Relative and random velocities within and between galaxies are discussed, and no indication is found for equipartition of energy between systems of different masses or for alteration of velocity dispersion by the formation and evolution of physical groupings, except for the rich clusters.

The redshifted 21-cm and Mg II absorption lines observed in the QSO 3C 286 and the BL Lacertae object 0735+178, respectively, are analyzed to determine the location of the absorbing gas. We first describe evidence which supports the presence of neutral hydrogen intrinsic to QSOs, and then examine excitation conditions influencing the formation of 21-cm absorption lines. Due to the high spin temperature T/subs/ resulting from the bright 21-cm continuum, the 21-cm absorption line observed in 3C 286 can arise close to the QSO only if L$alpha$ radiation determines the excitation of the hyperfine levels. The 21-cm line could also form in an intervening galaxy. The absence of redshifted Mg II absorption in the spectrum of 3C 286 places and upper limit of 3 x 10$sup -3$/T/ subs/ on the Mg$sup +$/H I. ratio in the column of absorbing H I. This is compatible with a solar abundance ratio of Mg/H; but if the observed upper limit to Mg II absorption were reduced by a factor 2, this would require Mg$sup +$/H I

James Trefil is well known as a science writer who can explain complex physics in simple ways. In "The Dark Side of the Universe" he has used his unusual talents to describe one of the latest of the problems that confront astronomers—the nature of the dark (invisible) matter, which many astronomers believe comprises the bulk of the mass and energy of the universe, and the way in which it bears on the structure and evolution of the universe. In a nutshell, his theme is that we all now believe that the universe started in a hot big bang (he quotes a 99% probability); that there is just enough mass in the universe so that it does not expand forever (that is, to close it); that most of this matter is not normal baryonic matter (protons, neutrons, and heavier nuclei); that we do not understand how galaxies of stars formed but are on the way to ...

This paper suggests a new and clear-cut way of deciding whether evolutionary effects are necessary to interpret the observed radio-source counts. To this end, a method is outlined for constructing the parent radio luminosity function from a complete sample of radio sources whose redshifts are all known. It is argued that if such a luminosity function can be constructed without evolutionary parameters, then evolutionary effects are not required. The method is illustrated by its applications to two well-known samples of radio sources. It is further shown that the nonevolving luminosity function satisfies the constraint of sky brightness and is consistent with the observed redshift-flux-density plot. Thus, it appears from these investigations that evolution is not required either in luminosity or in number density. 18 references.

The energy content of the compact incoherent electron-synchrotron sources 3C 84, 3C 120, 3C 273, 3C 279, 3C 454.3, CTA 102, 3C 446, PKS 2134+004, VRO 42.22.01 and OJ 287 is calculated on the assumption that the low-frequency turnovers in the radio spectrum are due to self-absorption and that the electron distribution is isotropic. The dependence of the source parameters on various modifications of the standard assumptions is determined. These involve relativistic motions, alternate explanations for the low-frequency turnover, proton-synchrotron radiation, and distance to the source. The canonical interpretation is found to be accurate in many respects; some of the difficulties and ways of dealing with them are discussed in detail.

Spectrograms of a number of objects identified with southern radio sources have been obtained with the 60-inch telescope of the Inter-American Observatory at Cerro Tololo, Chile. Redshifts have been measured for 10 radio galaxies, and the spectroscopic features are listed. Direct photographs of some of the objects are described. Spectrograms of four stellar objects suggested as QSO identifications showed all objects to be galactic stars, including one recently suggested as an identification for PKS 1302-49 instead of NGC 4945.

It is shown that the best-fitting slope of the redshift-magnitude relation for the most luminous quasi-stellar object in each redshift range is 4.3 plus or minus 0.4. However, the steepness of this slope is due primarily to the lowest redshift range including 3C 273, without which it is 2.1 plus or minus 0.6. The slopes of the second and third brightest QSOs are 3.1 plus or minus 0.6 and 3.2 plus or minus 0.6, respectively, markedly less than the slope of 5 which is expected for a Friedmann universe with q(0) = +1. Although the departure of the slope from 5 mag per decade is statistically significant at about 95% confidence, due to the heterogeneity and incompleteness of the sample there may be a systematic selectional bias not accounted for either in this analysis or in that of Bahcall and Hills. Consequently, no definite pronouncement can be made until a complete sample of adequate size is examined.

Cannon and Penston1 have reported observations of the rapid optical fluctuations of the quasi-stellar object 3C 446. These add further to the study of rapid variations discovered in this object by Sandage2 and followed in 1966 by Kinman, Lamla and Wirtanen3. Variations of this kind lead to the conclusion that the region which gives rise to the fluctuation is very small, and in general it is found that for this region R ⩽ c τ, where τ is the period over which a flux change has occurred. A detailed discussion of this result has been given by Terrell4 and others. These limitations lead to very restrictive conditions on the possible models of quasi-stellar objects which arise largely from the high radiation density that must be present in the continuum source. The upper limits to the sizes which have been used range from light months to light days (∼1017 — 1015 cm) and the corresponding lower limits to the energy densities are then in the range 10–105 erg/cm3 if the quasi-stellar objects are at cosmo-logical distances, and 10−3–10 ergs/cm3 if the objects lie at distances ∼ 10 megaparsec (Mpc). If the objects are at cosmological distances, then this radiation field is so intense that it would be self-destructive, whether it arises by the synchrotron process or from the inverse Compton process5,8. The difficulties that are encountered in arriving at satisfactory models, if the quasi-stellar objects are at cosmological distances, have been considered by Hoyle, Burbidge and Sargent5. Attempts to evade or to minimize these difficulties if the objects are at cosmological distances have been made by Rees6, by Woltjer7, and by Hoyle and Burbidge8, and they require that the radiating blobs are moving at relativistic speeds and/or that there is a large degree of directivity in the streams of relativistic electrons. If the quasi-stellar objects are much closer, the radiation density is accordingly reduced and the problems are less severe.

A summary of the estimates (made in 1958) of the total energy in particles and magnetic field in the non-thermal galactic and extragalactic sources are given. These estimates are obtained from calculations by the theory- of synchrotron radiation. (C.J.G.)