The pitfalls of astrobiogeography

Biogeography, the study of organismal distribution, adheres to the same basic reasoning no matter where organisms are distributed. Wickramasinghe and Wickramasinghe (Astrophys. Space Sci. doi:10.1007/s10509-008-9851-2), however, are possibly the first to propose a mechanism of distribution for extraterrestrial organisms, thus venturing into the uncharted realm of astrobiogeography. The same logic used in the study of distributions on Earth applies to those of extraterrestrial microbes. Herein we attempt to introduce some pitfalls common in biogeography for those venturing into the new study of astrobiogeography.     

Reply

A previous study of non-axisymmetric eigenmodes in a simple model plasmasphere is extended to a case in which the Alfvén speed varies across the magnetic field lines. An approximate ordinary differential equation is derived, and this contains a logarithmic singularity closely analagous to a result obtain by Tamao (1965). The singularity is found to lie close to the resonant lines of force for a hypothetical torsional oscillation. Some valid eigenfrequencies are stated for a region with appropriate further boundaries.     

Celestial mechanics: Past, present, future

Over all steps of its development celestial mechanics has played a key role in solar system researches and verification of the physical theories of gravitation, space and time. This is particularly characteristic for celestial mechanics of the second half of the 20th century with its various physical applications and sophisticated mathematical techniques. This paper is attempted to analyze, in a simple form (without mathematical formulas), the celestial mechanics problems already solved, the problems that can be and should be solved more completely, and the problems still waiting to be solved.     

Fundamental catalogues,past, present and future

Presented is a review of the main achievements of fundamental astrometry from earliest times through the present century. At all times the construction of a celestial reference coordinate system has tormed an important task for describing motions in the sky. The positions of fundamental stars and their centennial variations have been laid down in fundamental catalogues which-beginning with the 18th century-have facilitated famous discoveries and have given rise to the improvement of the techniques of observation. This review culminates in the documentation of the observational achievements of the latest 25 years where in a world-wide campaign of about 50 observatories considerable contributions have been made to the improvement of the current conventional reference coordinate system given in the Fourth Fundamental Catalogue (FK4). The observations analysed in an ambitious program at Heidelberg will yield the FK5 which also will introduce the System of Astronomical Constants adopted by the IAU in 1976. This report ends with an outlook on contributions of space techniques and of radioastrometry of extragalactic sources to progress in fundamental astrometry.Dedication: This review is an extended version of the Dirk Brouwer Lecture 1983 of the Division on Dynamical Astronomy of the American Astronomical Society. With the topics of this lecture the author honors Dirk Brouwer's contributions to astrometry and gratefully acknowledges the support given to astronomy by Ministerialdirigent Karl Otto Schlau in the Government of Baden-Württemberg, Stuttgart, Federal Republic of Germany.     

Authors' Reply

Abstract— Reimold et al. question our interpreted impact origin of the Fohn structure, Timor Sea, and criticise methodological aspects of the seismic reflection survey of Fohn structure and chemical analytical techniques. Our impact interpretation resulted from (1) remarkable analogies between the seismic structures of massive core‐annular trough structure of volcanic diatremes, and the syncline‐ringed central uplift of impact structures; (2) occurrence of Cretaceous microfossils in the drill chips, which suggested deep excavation; (3) lack of seismic evidence for volcanic feeders or conduits, and (4) the ultramafic chemistry of drill chips (Ni < 428 ppm; Co < 51 ppm; Cr < 518 ppm). Here we indicate that, since publication of our paper, we have uncovered in Fohn‐1 drill cuttings rare apatite‐rich lamproite mineral assemblages consisting of pseudomorphs of analcite after leucite, nontronite‐altered olivine, diopside, alkali pyroxene, Ti‐phlogopite, apatite, Mg‐ilmenite, priderite, rutile, and secondary barite. The new data explain the high gamma ray log anomalies in Fohn‐1 well and shed new light on the origin of the Fohn structure. Our error serves to clarify criteria for distinguishing between buried diatremes and impact structures.     

Authors' Reply

Abstract— Jull et al. propose an alternative interpretation of our depth vs. ¹⁴C data measured on a peat core from the central Tunguska impact site (Rasmussen et al., 1999). We find that the proposed alternative is untenable.     

Solar oscillations: Past,present, and future

Observation of global oscillations of the Sun constitutes a primitive seismology of the solar interior. The frequencies, if correctly identified with definite normal modes of vibration, provide a measure of the average velocity of sound in the interior and thereby of its composition and temperature. Fine structure in the frequencies of nonradial modes may provide information on their character (multiplicity) and on the rotation of the solar interior. Study of the amplitudes and phase fluctuations of the vibrations may clarify the excitation and damping of the vibrations.After a brief historical review emphasizing global velocity spectroscopy an account is given of the present status of the observations of global oscillations in the range of periods of 3 to 160 min.Finally the future capabilities of the observational techniques and their resultant potential is discussed.Proceedings of the 14th ESLAB Symposium on Physics of Solar Variations, 16–19 September 1980, Scheveningen, The Netherlands.     

Asteroseismology: Past, present and future

Asteroseismology studies stars with a wide variety of interior and surface conditions. For two decades asteroseismic techniques have been applied to many pulsating stars across the HR diagram. Asteroseismology is now a booming field of research with stunning new discoveries; I highlight a personal selection of these in this review, many of which are discussed in more detail elsewhere in these proceedings. For many years the Nainital-Cape Survey for northern roAp stars has been running at ARIES, so I emphasise new spectroscopic results for roAp stars and point out the outstanding prospects for the planned ARIES 3-m telescope at Devastai. High precision spectroscopy has revolutionised the asteroseismic study of some types of stars — particularly solar-like oscillators and roAp stars — while photometry is still the best way to study the frequency spectra that are the basic data of asteroseismology. New telescopes, new photometers and space missions are revolutionising asteroseismic photometry. In addition to the ground-based potential of asteroseismic spectroscopy, India has the knowledge and capability for space-based asteroseismic photometry. The future for asteroseismology is bright indeed, especially for Indian astronomers.     

Perspectives and challenges for future telescopes

At the celebration of 400 years of telescopic observations, it is appropriate to consider future ground-based facilities enabled by continuing technological developments, and driven by astronomical questions which are amongst the most fundamental in science and are of enormous interest to the general public.     

A configuration for future giant telescope

A configuration for the Future Giant Telescope is proposed. It is a 30m telescope with segmented primary mirror and alt-azimuth mounting. The aspherical f/1.2 primary mirror is made up of 1095 partial annular submirrors. The optical system includes a Nasmyth system, a coude system and a wide field system. The Nasmyth system has a novel design with four mirrors and provides a ∼10 arcmin field of diffraction-limited images, a much larger field than can be obtained by the traditional Nasmyth system. Several diffraction-limited observations each over a small field, can be carried out simultaneously. By applying active optics to change the shape, tip, tilt and piston of the submirrors, thereby to effect a new aspherical surface of the primary, excellent quality images can be obtained for the coude system and the wide field system. The wide field system has a field of 25 arcmin, the focal surface is only slightly curved and the atmospheric dispersion could be corrected. The tolerances of the surface shape and position for the submirrors, and the telescope mounting and structure are also discussed. The innovations in this configuration should have a general significance for future giant telescopes.     

Fundamental reference systems; Past,present, and future

The present fundamental reference system is defined by the FK5 Fundamental Reference Catalog and the associated IAU Resolutions of 1976 through 1982. The past is defined to be what preceded the present fundamental reference system and future is defined to be what ever will come after it. The resulting characteristics of the different fundamental reference systems are considered from the aspects of the observational data, the computational methods, and the underlying theories. Having developed an understanding of these operational fundamental reference systems, the desired properties of the ideal fundamental reference system are presented. Finally, some questions concerning the future fundamental reference system are presented.