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See detailL'astronomie dans le monde
Manfroid, Jean ULg

Article for general public (2005)

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See detailL'astronomie dans le monde
Manfroid, Jean ULg

in Ciel (Le) (2005), 67

Un noyau de galaxie orphelin, La Voie Lactée barrée, Millième pour SOHO, Spirit, Astéroïde 1998 SF36 Itokawa, Titan, Olivine dans Tempel 1, Explosion lointaine

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See detailL'Astronomie des anciens
Nazé, Yaël ULg

Article for general public (2010)

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See detailL'Astronomie des anciens
Nazé, Yaël ULg

Article for general public (2009)

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See detailL'astronomie des Anciens
Nazé, Yaël ULg

Book published by belin (2009)

Quelle que soit la civilisation à laquelle il appartient, l'etre humain cherche dans le ciel des réponses aux questions qu'il se pose sur son origine, son avenir et sa finalité. Le premier mérite de ce ... [more ▼]

Quelle que soit la civilisation à laquelle il appartient, l'etre humain cherche dans le ciel des réponses aux questions qu'il se pose sur son origine, son avenir et sa finalité. Le premier mérite de ce livre est de nous rappeler que l'astronomie a commencé ainsi à travers les mythes célestes imaginés par les Anciens pour expliquer l'ordre du monde et la place qu'ils y occupaient. Mais les savoirs astronomiques passés étaient loin d'etre négligeables et certainement pas limités aux seuls travaux des Grecs : c'est ce que l'auteur montre à travers une passionnante enquete, de Stonehenge à Gizeh en passant par Pékin et Mexico, fondée sur l'étude des monuments anciens et des sources écrites encore accessibles. Les tablettes mésopotamiennes, les annales chinoises, les chroniques médiévales, etc. sont en outre d'une singulière utilité pour les astronomes modernes : comment sinon remonter aux variations de la durée du jour au cours des siècles, ou percer la nature de l'explosion qui a frappé tant d'observateurs en 1054 ? Ce livre offre un voyage magnifiquement illustré à travers les âges, entre astronomie et archéologie. [less ▲]

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See detailL'astronomie des Grecs
Le Paige, Constantin ULg

Speech (1895)

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See detailAstronomie en Terres d'Islam. Lumières sur la sacralisation de l'espace et du temps
Biémont, Emile ULg

Book published by Burillier, Vannes (2006)

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See detailAstronomie et chronoligie chez Newton - arguments astronomiques à l'appui de la chronologie de Newton
Nazé, Yaël ULg

in Archives Internationales d'Histoire des Sciences (2012), 62(169), 717-765

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See detailAstronomie et géodésie : Trois conférences (mars et avril 1964)
Swings, Polydore ULg; Grognard, René

Book published by Université de Liège. Institut d’Astrophysique (ULg) (1964)

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See detailAstronomie et religion
Nazé, Yaël ULg

Article for general public (2009)

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See detailL'astronomie moderne
Le Paige, Constantin ULg

Speech (1897)

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See detailAstronomy for the under tens -- P. Moore
Manfroid, Jean ULg

in Ciel et Terre (1986), 102

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See detailAstronomy with your personal computer -- P. Duffet-Smith
Manfroid, Jean ULg

in Ciel et Terre (1987), 103

Not Available

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See detailAstrophysical Concepts, seconde édition -- Martin Harwit
Manfroid, Jean ULg

in Ciel et Terre (1989), 105

Not Available

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See detailAstrophysical parameters and multiplicity of massive stars: a mathematical approach
Mahy, Laurent ULg

Doctoral thesis (2011)

Often quoted for their crucial role in the ecology of galaxies, massive stars remain mysterious. The exact process leading to their formation, their stability or their stellar winds are so many questions ... [more ▼]

Often quoted for their crucial role in the ecology of galaxies, massive stars remain mysterious. The exact process leading to their formation, their stability or their stellar winds are so many questions which are still unanswered. Since the lifetime of these objects is too short to allow them to move far away from their birth places, the large majority of massive stars are located in young open clusters or in OB associations. The observations of massive stars in these locations thus provide with promising information on their formation mechanisms. One of the most interesting properties, in this context, is their multiplicity. Indeed, the proportion of multiple systems, the values of orbital periods, of eccentricities, or of mass ratios are parameters directly linked to the formation mechanism and to the dynamical interactions occurring during the earliest stages of their existence. Moreover, constraining this multiplicity with a sufficient accuracy allows to obtain a better determination of the nature and physical parameters of massive stars. The present work is devoted to the study of the O star populations located in the young open cluster NGC2244 and in the surrounding Mon OB2 association as well as in several OB associations of the Cygnus complex. We establish not only the multiplicity of about thirty stars but also their fundamental parameters such as their masses or their N content. However, the complexity of observed spectra of multiple systems makes these objects difficult to investigate. Their analysis thus requires the development and the utilization of mathematical tools such as the "disentangling" which allows to separate the spectra of the components from the observed ones or such as the Doppler tomography which aims at mapping the wind interactions seen in some binary systems. The first part of this dissertation is dedicated to the development and to the characterization of these mathematical methods whilst the second part focuses on the study of populations of massive stars. We refine the orbital and physical parameters of systems already known as multiple. In this context, the analysis of the two components of LZ Cep system reveals modified abundances for the secondary star, confirming a mass transfer from the secondary towards to primary. We also detect for the first time a third star in the HD150136 system. This object, composed of an O3, an O5.5 and an O6.5, constitutes a new test to apply these mathematical methods and thus to better constrain the physical properties of the system as well as those of each component. Moreover, we find, in the population of NGC2244, of Mon OB2 and of the Cygnus OB associations, six new binary systems and derive the orbital solutions for five of them. These results show that NGC2244 hosts only one long-period binary and none with a short period whilst four short-period and no long-period systems are detected in the Cygnus complex. This obvious lack of short-period system in NGC2244 contrasts with the O star populations in other young open clusters such as NGC6231 or IC 2944. Besides the multiplicity, the fundamental parameters such as the N content also allows us to, notably, adapt the so-called Hunter-diagram to galactic O stars. Moreover, we have obtained photometric data for six O-type stars in NGC2244 and Mon OB2 with the CoRoT satellite. These data of unprecedented quality allow us to detect the presence, in the O star light curves, of red noise which is supposed to originate from either the sub-surface convection zone, the granulation or an onset of clumping in the winds of the stars. We also highlight the existence of non-radial pulsations in the light curve of Plaskett’s Star as well as a hot spot located between the two components of that system. In addition, numerous frequencies, extracted from the CoRoT light curves, reveal, for some of the observed stars, solar-like oscillations or beta Cephei-like pulsations. This analysis thus gives a first observational constraint on the bright end of the massive star instability strip. [less ▲]

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See detailAstrophysical research in France in 1940-1942.
Swings, Polydore ULg

in Astrophysical Journal (1944), 99

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See detailAstrophysical studies of extrasolar planetary systems using infrared interferometric techniques
Absil, Olivier ULg

Doctoral thesis (2006)

The study of extrasolar planetary systems has thrived during the last two decades, stimulated by the discovery of circumstellar dust and extrasolar planets around main sequence stars. However, direct ... [more ▼]

The study of extrasolar planetary systems has thrived during the last two decades, stimulated by the discovery of circumstellar dust and extrasolar planets around main sequence stars. However, direct imaging of planetary systems has been possible in only very special cases so far due to the huge contrast and to the small angular separation between stars and their environments. Even for these favourable cases, the inner regions where terrestrial planets are expected to be forming and where life could develop have not been investigated yet due to the lack of appropriate tools. Infrared interferometry is a very promising technique in this context, as it provides the required angular resolution to separate the emissions from the star and its immediate neighbourhood. The present work aims at developing the high dynamic range capabilities of interferometric techniques for the characterisation of planetary systems. As a first step, we demonstrate that current interferometric facilities have the potential of detecting dust in the first few astronomical units of massive debris disks around nearby stars. Our observations of Vega with the FLUOR near-infrared beam combiner at the CHARA Array reveal the presence of warm dust responsible for a K-band flux 78 times fainter than the stellar photospheric emission. In order to extend the imaging of planetary systems to fainter disks and to giant extrasolar planets, we investigate in a second step the performance of future ground-based nulling interferometers, taking into account atmospheric eff ects in a realistic way. Our simulations show that a nulling instrument installed at the ESO Very Large Telescope Interferometer would detect circumstellar features as faint as a few 10^-4 of the stellar flux. Finally, the third part of this work focuses on the implementation of nulling interferometry on future space-borne missions, the goal being to characterise extrasolar planets with sizes down to that of the Earth. [less ▲]

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See detailAstrophysics and industry
Swings, Polydore ULg

in Leaflet - Astronomical Society of the Pacific (1953), 6(286), 283-290

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See detailAstrophysics, and how to attract young people into Physics
Nazé, Yaël ULg; Stavinschi, Magda; Vanherck, Martine ULg

Book (2005)

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See detailAstrophysics: 1951
Swings, Polydore ULg

in Leaflet - Astronomical Society of the Pacific (1952), 6(273), 178-188

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