Van Biesbroeck Research Articles

Donat Gotthard Wentzel

Donat Gotthard Wentzel

Een machtige veropenbaring der jeugdige Gentsche kunst. Publieke kunst in het kader van de Gentse Wereldtentoonstelling van 1913.

The Ghent World Fair, organized in 1913, was a great opportunity for the city to encourage the realization of public art, both on the exhibition grounds as in the city center. Already in 1911, the local press expressed its concern about the assignment of a public commission to two Brussels artists and insisted that the young and talented Ghent sculptors should not be overlooked. Though no traces of a structural, strategic commissioning program were found, the organizing committee lavishly granted this request by almost exclusively selecting Ghent sculptors for the main sculptural assignments, such as Geo Verbanck for the Monument for the Brothers Van Eyck, Alois De Beule for The Steed Beyaert, and Jules Van Biesbroeck (jr.) for Beauty, Strength and Wisdom. Moreover, almost all these sculptors were closely associated with members of the organizing committee, for instance belonging to the same guild or committees, or with each other, having shared mutual commissions, teachers, etc. This chapter offers an overview of the public commissions at the Ghent World Fair, and elucidates their organization, representation, reception and fate during and after the Fair. Furthermore, the exterior and interior decorations of most of the exhibition pavilions, including wall paintings, decorative reliefs, etc., are discussed. These commissions for pavilion decorations were often also assigned to local artists, with only a few exceptions. Only the decoration of the pavilions of foreign nations, some smaller commissions, and the casting of the bronzes were executed by city-outsiders. Moreover, local, ‘modern’ artists, such as George Minne, were surpassed for the public art commissions in favour of sculptors with a more academic style, belonging to the same network. Consequently, the international ambitions of the World Fair were mainly substantiated by local, traditional-style sculptors. As was the case for past and future World Fairs, the public art at the Ghent World Fair generated questions about traditionalism and modernity, as well as the balance between local, national and international ambitions and concerns.

The NASA Astrophysics Data System

The NASA Astrophysics Data System (ADS) is a digital library for researchers in astronomy and astrophysics. It also covers other subject areas, such as electrical engineering, geophysics, physics, and instrumentation, as they are all loosely related to astronomy and astrophysics. This data system is a NASA funded project and access to all ADS services is free to everybody, through the Internet.The value of the ADS to astronomical and astrophysical research has been widely recognised, both within the astronomical field, and by libraries. In 2001 Guenther Eichhorn, Project Scientist for ADS, received the Physics, Astronomy and Mathematics Division Award from the Special Libraries Association, and the 2001 van Biesbroeck Prize of the American Astronomical Society was awarded to Michael Kurtz, Scientist with the Harvard-Smithsonian Center for Astrophysics (ADS Awards and Recognition).The digital library contains over 3.3 million records, which are stored in four databases...

AAS Acknowledges Achievements in Astronomy

The American Astronomical Society recently announced the winners of several of its awards for 2001. These awards recognize contributions to astronomy and astrophysics. The Henry Norris Russell Lectureship, the society’s highest honor, will be presented to Wallace L. W. Sargent, Ira S. Bowen Professor of Astronomy at Caltech. AAS praises Sargent for being an “intellectual leader and educator” throughout his career and recognizes his contributions to astronomical spectroscopy, including his work in stellar spectroscopy of A-type stars that “led to the discovery of the helium-3 isotope in star 3 Centauri A.” He involved many of his students in his work in extragalactic spectroscopy, “which produced the first evidence for a black hole in galaxy M87 and culminated with his studies of quasar absorption lines.” His demonstration that the Lymanalpha forest absorption arises from intergalactic primordial gas clouds “provided a fundamental new probe of primeval gas in the early universe.”The society is presenting a new award this year. The inaugural AAS Education Prize, given in recognition of outstanding contributions to the education of the public, of students, and the next generation of professional astronomers, will go to Frank D. Drake for his “inspiration and leadership in many areas of education and public outreach in astronomy.” Drake’s “wide-ranging popularizations, his tireless help for journalists, and his championship of education and public information through the SETI Institute have helped scientists, educators, and the world at large to think rationally about life in the cosmos.” The citation also noted that his course work for and mentorship of students, and his development of the science of SETI (the search for extraterrestrial intelligence) through Project Ozma, the Drake Equation, and Project Phoenix, have “brought the excitement of the cosmic quest to several generations.” Drake is a professor emeritus of astronomy and astrophysics at the University of California, Santa Cruz, and distinguished scientist and chairman of the board of trustees of the SETI Institute. Bruce Elmgreen, a research staff member at IBM’s T. J. Watson Research Center in Yorktown Heights, New York, will receive the Dannie Heineman Prize for Astrophysics, given jointly by AAS and the American Institute of Physics. Elmgreen is being recognized for contributions that “span a remarkable range from theoretical studies of key processes in the interstellar medium to the physics of galaxy-wide starbursts, to investigations of dynamical features, including spiral arms and bars in galaxies.” The Newton Lacy Pierce Prize will be given this year to Kenneth Sembach, a research scientist at Johns Hopkins University. Sembach is being acknowledged for work “that has been important in increasing our understanding of the structure and elemental abundances of the gaseous component of the Galaxy, especially of the galactic halo, as well as in discovering new facets of the high-velocity cloud phenomenon in the galactic periphery.” Uros Seljak will receive the Helen B. Warner Prize for Astronomy for his “contributions to the theoretical understanding of the cosmic microwave background anisotropies and to the development of numerical and analytical tools that have been widely adopted for the comparison of observational data and cosmological models in that area.” Seljak is an assistant professor of physics at Princeton University. Michael J. Kurtz, an astronomer and computer scientist at the Harvard–Smithsonian Center for Astrophysics in Cambridge, Massachusetts, will be awarded the George Van Biesbroeck Prize. AAS acknowledges Kurtz’s contributions as “the visionary designer of the Astrophysics Data System, which clearly has revolutionized for over a decade the speed and thoroughness in which astronomers now can search and access the vast and still growing technical literature.”The Bruno Rossi Prize, given by AAS’s high-energy astrophysics division, will be shared by Andrew Fabian and Yasuo Tanaka for “their discovery, with the ASCA satellite [Advanced Satellite for Cosmology and Astrophysics], of broad iron K lines in active galactic nuclei, which demonstrate the effects of the strong gravitational field characteristic of black holes.” Fabian is a Royal Society Research Professor with the Institute of Astronomy at the University of Cambridge, UK. Tanaka is a professor emeritus of astronomy and astrophysics at the Institute of Space and Astronautical Science in Sagamihara, Japan. Sargent PPT|High resolution© 2001 American Institute of Physics.

Summary and Reflections

Let me begin by taking a very broad historical perspective on the study of pre-main-sequence binaries. You have seen reference several times at this meeting to that first paper on T Tauri binaries by Joy & Van Biesbroeck (1944). Following that paper there followed a long period that might be called the Decades of Ignorance. I refer here to a period of time in the study of star formation where we largely ignored the fact that we knew that most stars were binaries. The high frequency of binaries among stars is something that we've known for a very long time, well over a century. Indeed, looking back, it is remarkable that the paper in 1982 by Mel Dyck and his collaborators identifying T Tauri as a binary caused such a stir. This paper is sometimes cited as the birth of modern research into young binaries. But how many of our colleagues in the realm of main-sequence binaries had already told us over and over again that most of these young stars had to be binaries? Of course, the reason this important paper caused much ado was in part because T Tauri is the very prototype star of star-formation study.

Binary Stars: Historical Milestones

This is a brief historical review of the discovery of binary stars, starting in the 18th and 19th century with the work of W. Herschel, W. Struve, and their famous sons. I describe how Ch. Doppler in 1842 found the Doppler effect in connection with the colours of double stars. I also describe how the observation of the stationary Calcium H and K lines in the spectrum of the spectroscopic binary δ Ori led to the discovery of the interstellar medium by J. Hartmann in 1904 with the Potsdam refractor. Some steps in the discovery of young binary stars are recounted, starting with the paper of Joy and van Biesbroeck in 1944. The history of ideas regarding the origin of binary systems is also briefly reviewed, beginning with J. Michell's statistical argument in 1767 that many close visual pairs of stars must indeed form physical systems, and W. Herschel's definition of a binary star as “a real double star - the union of two stars that are formed together in one system, by the laws of attraction”.

The Coolest Isolated M Dwarf and Other 2MASS Discoveries

We have obtained follow-up spectroscopy of eight late dwarf candidates discovered in a 105 deg2 area observed with the 2MASS Prototype Camera during test runs between 1992 and 1994. These objects were chosen because of their red infrared colors (e.g., J-Ks ≥ 1.10) and/or red OIR colors (e.g., R-Ks ≥ 6.00). All eight are late M dwarfs, six of which have spectral types later than van Biesbroeck 8 (type M7 V). Despite the fact that we have only followed up a fraction of the reddest sources discovered, the number of known M dwarfs of type M7 and cooler has been increased by 30%. Extrapolation of these results alone shows that over 2000 dwarfs of similar spectral type and with Ks ≤ 14.0 will be imaged by 2MASS over the entire sky. One of these new discoveries is astonishingly cool and has a tentative type of ≥M10 V. This dwarf, one of the least luminous objects yet discovered, could itself be a high-mass brown dwarf, thus providing another empirical data point in a regime where few such objects are now recognized. Only the substellar suspect GD 165 B and the bona fide brown dwarf GL 229 B, both discovered as companions to known stars, are cooler. Thus, this 2MASS discovery becomes the coolest isolated object so far identified.

Pre-Main-Sequence Binary Stars

The observational study of pre-main-sequence (PMS) binary stars is in many ways a very young field; most PMS binaries known today were discovered in the past decade. Nonetheless, T Tauri stars have been under study for more than a half century, and the serendipitous discovery of visual pairs has always been a by-product of their observation (e.g. Joy & Van Biesbroeck 1944). The acceleration of discovery in recent years has at least two stimuli, one technical and one sociological. First, the frequency of binaries among main-sequence solar-type stars peaks at semimajor axes of order 50 AU, projecting to less than 0.5 at the distance of the nearest star-forming regions. The requisite high­ angular-resolution techniques (and near-infrared detectors) have only recently permitted the major surveys for PMS binaries now coming to fruition. Second, and equally important, the formation and early evolution of binaries has attracted increasing attention from those studying star formation. This can perhaps be attributed to both a growing confidence in our general picture for single-star formation (e.g. Shu et a1 1987) and recognition that however correct our theories of single-star formation may be, the usual product of a star-formation event is a multiple-star system. Until recently, the primary observational constraint on the mechanisms of binary formation and early evolution have been provided by main-sequence (MS) binaries in the solar vicinity, acting as a surrogate for the zero-age-main­ sequence (ZAMS) binary population. As the ultimate product of the binary formation process, ZAMS binaries do supply essential constraints. However,

The Luminosity Function of White Dwarfs in the Local Disk and Halo

The luminosity function (LF) and total space density of white dwarfs in the solar neighborhood contain important information about the star formation history of the stellar population, and provide an independent method of measuring its age. The first empirical estimates of the LF for degenerate stars were those of Weidemann (1967), Kovetz and Shaviv (1976) and Sion and Liebert (1977). The follow-up investigations made possible by the huge Luyten Palomar proper motion surveys, however, added many more faint white dwarfs to the known sample. While the number of known cool white dwarfs grew to nearly one hundred, these did not include any that were much fainter intrinsically than the coolest degenerates found from the early Luyten, van Biesbroeck and Eggen-Greenstein lists.

Low luminosity stars: How no(w) brown dwarfs?

Low luminosity stars: How no(w) brown dwarfs?

Review of methodology and technology available for the detection of extrasolar planetary systems

Anyone undertaking an interstellar voyage might wish to be assured of the existence of a safe planetary harbor at the other end! Aside from the obvious interest of the participants in this Symposium, astronomers and astrophysicists are also eager to detect and study other planetary systems in order to better understand the formation of our own Solar System. Scientists involved in the search for extraterrestrial intelligence argue that planets suitable for the evolution of life may abound elsewhere within our own Milky Way Galaxy. On theoretical grounds, they are probably correct, but they lack any observational support. For inspite of decades of claimed astrometric detections of planetary companions and the recent exciting and tantalizing observations from the IRAS satellite and the IR speckle observations of Van Biesbroeck 8 and other cool stars, there is no unambiguous proof for the existence of another planetary system beyond our own. In this paper we review the various methods for detecting extrasolar planets and briefly describe the Earth and space based technology currently available and discuss the near-term plans to implement these different search techniques. In each case an attempt is made to identify the limiting source of systematic error inherent to the methodology and to assess the potential for technological improvements.

On the nature of the companion to Van Biesbroeck 8

We present here the results of the first numerical evolutionary calculations for very low-mass stars (masses in the range of 0.01–0.1 M⊙) with ages up to the age of the Galaxy. Our calculations shed new light on the nature of the recently discovered object VB 8B (ref. 1), the companion to Van Biesbroeck's star no. 8 (VB8; ref. 2), and support the identification1 of this object as a low-mass star in which hydrogen burning was never able to establish thermal equilibrium. For plausible ages of this binary stellar system (≳109 yr), we estimate the mass, M, of VB 8B to be in the range 0.04–0.08 M⊙ (see also ref. 1 and refs therein). The object is supported primarily by degenerate electron pressure, and we find that its present values of central density and temperature are ρc ≃ 500–2,000 g cm−3 and Tc ≃ 1.0−1.5 × 106 K, respectively. The star VB8 itself3–5 may also be a low-mass star which marginally failed to establish main-sequence hydrogen burning. Thus, the mass ratio for this binary system is probably not greatly different from unity, and we predict an orbital period of ≳40yr. Our evolutionary tracks are also applicable to the interpretation of observations of other very low-luminosity dwarfs (see refs 3, 5–7). The study of such objects may be directly relevant to the development of an understanding of the ‘dark matter’ that has been inferred, from dynamical considerations, to be present in our Galaxy and many extragalactic systems (see, for example, refs 8, 9).

Infrared detection of a close cool companion to Van Biesbroeck 8

view Abstract Citations (63) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Infrared detection of a close cool companion to Van Biesbroeck 8. McCarthy, D. W., Jr. ; Probst, R. G. ; Low, F. J. Abstract The authors have detected, via infrared speckle interferometry, a cool object 1arcsec from the very low-luminosity star VB 8, 3 mag fainter than VB 8 at 2.2 μm. Measurements at 1.6 and 2.2 μm give Te = 1360K and (assuming a physical association) R = 0.09 R_sun;, L = 3×10-5L_sun;, consistent with a substellar brown dwarf. These observations may constitute the first direct detection of an extrasolar planet. Publication: The Astrophysical Journal Pub Date: March 1985 DOI: 10.1086/184432 Bibcode: 1985ApJ...290L...9M Keywords: Companion Stars; Cool Stars; Extrasolar Planets; Infrared Stars; Late Stars; Stellar Mass; Astrometry; Brown Dwarf Stars; Infrared Interferometers; Astrophysics full text sources ADS | data products SIMBAD (3)

More Than a Planet, Almost a Star

More Than a Planet, Almost a Star

Planet discovered outside solar system

Astronomers have reported the discovery of a planet orbiting a star outside our solar system, which, if verified, would be the first time that a direct observation has been made. Using a relatively new technique called speckle interferometry, astronomers from the University of Arizona and the National Optical Astronomy Observatories (NOAO) have identified what they believe to be a planet similar to Jupiter, but with a much larger mass, orbiting the star Van Biesbroeck 8 (VB 8), which is located some 21 light‐years from earth in the Milky Way constellation Ophiuchus. Confirmation of this discovery, says the National Science Foundation, “would climax a centuries‐old quest to find such a body.”Another group of astronomers from the U.S. Naval Observatory, however, says the object orbiting VB 8 cannot be classified as a planet but fits the definition of a Brown Dwarf. According to the Naval Observatory, “Brown Dwarfs are loosely defined as objects too low in mass to be undergoing thermonuclear fusion, and hence cannot be called stars, and yet massive enough to be generating energy on their own.”

What is a planet” When is a discovery?

The news item above reports on the sighting of a planet outside our solar system, the first time such a discovery has been made. As with many scientific discoveries, however, things are not quite as simple as they seem. The problem with this discovery is that the two groups of astronomers invoked cannot quite agree on who saw what first. Or to put it another way: When is a planet not a planet but a Brown Dwarf and when is a discovery not a discovery but a confirmation? Astronomers from the U.S. Naval Observatory and the University of Arizona are having a little trouble sorting this out.Both groups do agree on the data. A substellar body has been directly and indirectly observed orbiting the intrinsically faint star Van Biesbroeck 8 (VB S) in a constellation of the Milky Way. In fact, both groups agree that the observed substellar body can be called a Brown Dwarf. The definition of a Brown Dwarf, it is agreed, lies somewhere in between the definition of a planet and that of a star. Herein lies the crux: can a Brown Dwarf be called a planet? Richard Harrington, an astronomer with the U.S. Naval Observatory, says that a Brown Dwarf is not a planet. Donald McCarthy, of the University of Arizona, says that it is.

Spectroscopy of faint asteroids, satellites, and comets

view Abstract Citations (9) References (19) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Spectroscopy of faint asteroids, satellites, and comets Degewij, J. Abstract Nineteen asteroids with orbital elements comparable to those of short-period comets and the outer Jovian satellites J6 Himalia and J7 Elara have been observed with the 228-cm telescope and image-tube spectrograph of Steward Observatory. No activity indicating cometary outgassing was detected. If comets are being perturbed into asteroidal orbits, then this lack of activity can be explained by an apparently short transition time between active and extinct phase. In addition, spectra of the faint comets Sanguin 1977p, Chernykh 1977l, Arend-Rigaux 1950 VII, West 1978a, and van Biesbroeck 1954 IV were obtained, showing CN(0,0) and in some cases C2(1,0) and C3 emission. Comet Arend-Rigaux was active again in the fall of 1977 and Comet West showed on May 31, 1978 a weak tail at a distance from the sun of 6.0 AU. Publication: The Astronomical Journal Pub Date: October 1980 DOI: 10.1086/112814 Bibcode: 1980AJ.....85.1403D Keywords: Asteroids; Astronomical Spectroscopy; Comets; Natural Satellites; Orbital Elements; Spectrum Analysis; Emission Spectra; Image Tubes; Outgassing; Spectrographs; Telescopes; PLANETS; SATELLITES; COMETS; ASTEROIDS; SPECTROSCOPY; HIMALIA; ELARA; JUPITER; PERTURBATIONS; SPECTRUM; SANGUIN COMET; CHERNYKH COMET; AREND-RIGAUX COMET; WEST COMET; VAN BIESBROECK COMET; CYANIDE; EMISSIONS; EQUIPMENT; DATA; OBSERVATIONS; DISTRIBUTION; ANALYSIS; MEIER COMET; COMPARISONS; SHORT-PERIOD COMETS; INTENSITY; WAVELENGTHS; GASES; SPECTROPHOTOMETRY; REFLECTANCE; Astronomy; Planets full text sources ADS |

Multiple systems of astrophysical interest. I

view Abstract Citations (18) References (34) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Multiple systems of astrophyical interest. I. Eggen, O. J. Abstract This paper reviews previous observations of the multiple systems Wolf 629/630, Mu Her BC, CM Dra ABC, Alpha Cen, 95 Cet AB, and ADS 16644. All these systems contain low-luminosity dwarfs or degenerate stars, and all except Mu Her BC, 95 Cet AB, and ADS 16644 involve flare stars. Parameters of the different systems and components are discussed and compared. It is suggested that there may be at least three sources of flare activity on late-type dwarfs and that the flare-star status of Proxima Cen may be a consequence of the star's low mass. Publication: The Astrophysical Journal Pub Date: December 1978 DOI: 10.1086/156620 Bibcode: 1978ApJ...226..405E Keywords: Dwarf Stars; Stellar Spectrophotometry; Variable Stars; Late Stars; Star Clusters; Stellar Luminosity; Stellar Motions; Van Biesbroeck Star; Astrophysics; Low-Luminosity Stars:Multiple Stars full text sources ADS | data products SIMBAD (10) GCPD (1) Related Materials (2) Part 2: 1982ApJ...258..605E Part 3: 1986AJ.....92..125E

Orbit of comet 1911 VI /Quenisset/

view Abstract Citations (3) References (5) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Orbit of comet 1911 VI (Quénisset). van Biesbroeck, G. ; Vesely, C. D. ; Marsden, B. G. Abstract The orbital elements by Kuhne (1914) have been improved by the use of 205 observations covering the interval from Sept. 24, 1911, to Jan. 24, 1912. Perturbations by all nine planets were taken into account. The 'original' and 'future' values of the reciprocal semimajor axis are found to be plus 0.002494 and plus 0.002764 (plus or minus 0.000016 m.e.) per AU, respectively. Publication: The Astronomical Journal Pub Date: December 1974 DOI: 10.1086/111700 Bibcode: 1974AJ.....79.1455V Keywords: Comets; Orbit Perturbation; Orbital Elements; Solar Orbits; Comet Tails; Perihelions; Visual Observation; Astronomy full text sources ADS |

Evolution of Low-Mass Stars. V. Minimum Mass for the Deuterium Main Sequence

An evolutionary sequence of stellar models has been calculated to determine the minimum mass and maximum time duration of stars on the low-mass end of the deuterium main sequence. The chemical composition chosen is (X = 0.68, Y = 0.29), with the terrestrial value XD = 1.9 x and l!Hp = 1. Evolutionary tracks have been calculated for 0.008, 0.01, 0.012, 0.015, and 0.02 M0. The mass limit for the deuterium main sequence is at or slightly below 0.012 M0, and the maximum time duration is 7.5 x 10 years. The luminosity of the minimum-mass deuterium-burning model is very slightly higher than that of the minimum-mass hydrogen-burning model, with a Tv smaller by soo K. The low-mass ends of the deuterium and hydrogen main sequences thus bracket the observations of Van Biesbroeck's star and W359. Stars with masses M %< 0.01 M0 enter strong deuterium-burning phases, but do not stabilize in a main-sequence configuration. Subject headitigs: interiors, stellar late-type stars pre-main-sequence stars