July 2019 BRAS Newsletter
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Mathématiques Et Espace
Atelier disciplinaire AD 5 Mathématiques et Espace Anne-Cécile DHERS, Education Nationale (mathématiques) Peggy THILLET, Education Nationale (mathématiques) Yann BARSAMIAN, Education Nationale (mathématiques) Olivier BONNETON, Sciences - U (mathématiques) Cahier d'activités Activité 1 : L'HORIZON TERRESTRE ET SPATIAL Activité 2 : DENOMBREMENT D'ETOILES DANS LE CIEL ET L'UNIVERS Activité 3 : D'HIPPARCOS A BENFORD Activité 4 : OBSERVATION STATISTIQUE DES CRATERES LUNAIRES Activité 5 : DIAMETRE DES CRATERES D'IMPACT Activité 6 : LOI DE TITIUS-BODE Activité 7 : MODELISER UNE CONSTELLATION EN 3D Crédits photo : NASA / CNES L'HORIZON TERRESTRE ET SPATIAL (3 ème / 2 nde ) __________________________________________________ OBJECTIF : Détermination de la ligne d'horizon à une altitude donnée. COMPETENCES : ● Utilisation du théorème de Pythagore ● Utilisation de Google Earth pour évaluer des distances à vol d'oiseau ● Recherche personnelle de données REALISATION : Il s'agit ici de mettre en application le théorème de Pythagore mais avec une vision terrestre dans un premier temps suite à un questionnement de l'élève puis dans un second temps de réutiliser la même démarche dans le cadre spatial de la visibilité d'un satellite. Fiche élève ____________________________________________________________________________ 1. Victor Hugo a écrit dans Les Châtiments : "Les horizons aux horizons succèdent […] : on avance toujours, on n’arrive jamais ". Face à la mer, vous voyez l'horizon à perte de vue. Mais "est-ce loin, l'horizon ?". D'après toi, jusqu'à quelle distance peux-tu voir si le temps est clair ? Réponse 1 : " Sans instrument, je peux voir jusqu'à .................. km " Réponse 2 : " Avec une paire de jumelles, je peux voir jusqu'à ............... km " 2. Nous allons maintenant calculer à l'aide du théorème de Pythagore la ligne d'horizon pour une hauteur H donnée. -
Lurking in the Shadows: Wide-Separation Gas Giants As Tracers of Planet Formation
Lurking in the Shadows: Wide-Separation Gas Giants as Tracers of Planet Formation Thesis by Marta Levesque Bryan In Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy CALIFORNIA INSTITUTE OF TECHNOLOGY Pasadena, California 2018 Defended May 1, 2018 ii © 2018 Marta Levesque Bryan ORCID: [0000-0002-6076-5967] All rights reserved iii ACKNOWLEDGEMENTS First and foremost I would like to thank Heather Knutson, who I had the great privilege of working with as my thesis advisor. Her encouragement, guidance, and perspective helped me navigate many a challenging problem, and my conversations with her were a consistent source of positivity and learning throughout my time at Caltech. I leave graduate school a better scientist and person for having her as a role model. Heather fostered a wonderfully positive and supportive environment for her students, giving us the space to explore and grow - I could not have asked for a better advisor or research experience. I would also like to thank Konstantin Batygin for enthusiastic and illuminating discussions that always left me more excited to explore the result at hand. Thank you as well to Dimitri Mawet for providing both expertise and contagious optimism for some of my latest direct imaging endeavors. Thank you to the rest of my thesis committee, namely Geoff Blake, Evan Kirby, and Chuck Steidel for their support, helpful conversations, and insightful questions. I am grateful to have had the opportunity to collaborate with Brendan Bowler. His talk at Caltech my second year of graduate school introduced me to an unexpected population of massive wide-separation planetary-mass companions, and lead to a long-running collaboration from which several of my thesis projects were born. -
The Dunhuang Chinese Sky: a Comprehensive Study of the Oldest Known Star Atlas
25/02/09JAHH/v4 1 THE DUNHUANG CHINESE SKY: A COMPREHENSIVE STUDY OF THE OLDEST KNOWN STAR ATLAS JEAN-MARC BONNET-BIDAUD Commissariat à l’Energie Atomique ,Centre de Saclay, F-91191 Gif-sur-Yvette, France E-mail: [email protected] FRANÇOISE PRADERIE Observatoire de Paris, 61 Avenue de l’Observatoire, F- 75014 Paris, France E-mail: [email protected] and SUSAN WHITFIELD The British Library, 96 Euston Road, London NW1 2DB, UK E-mail: [email protected] Abstract: This paper presents an analysis of the star atlas included in the medieval Chinese manuscript (Or.8210/S.3326), discovered in 1907 by the archaeologist Aurel Stein at the Silk Road town of Dunhuang and now held in the British Library. Although partially studied by a few Chinese scholars, it has never been fully displayed and discussed in the Western world. This set of sky maps (12 hour angle maps in quasi-cylindrical projection and a circumpolar map in azimuthal projection), displaying the full sky visible from the Northern hemisphere, is up to now the oldest complete preserved star atlas from any civilisation. It is also the first known pictorial representation of the quasi-totality of the Chinese constellations. This paper describes the history of the physical object – a roll of thin paper drawn with ink. We analyse the stellar content of each map (1339 stars, 257 asterisms) and the texts associated with the maps. We establish the precision with which the maps are drawn (1.5 to 4° for the brightest stars) and examine the type of projections used. -
Durham E-Theses
Durham E-Theses First visibility of the lunar crescent and other problems in historical astronomy. Fatoohi, Louay J. How to cite: Fatoohi, Louay J. (1998) First visibility of the lunar crescent and other problems in historical astronomy., Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/996/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk me91 In the name of Allah, the Gracious, the Merciful >° 9 43'' 0' eji e' e e> igo4 U61 J CO J: lic 6..ý v Lo ý , ý.,, "ý J ýs ýºý. ur ý,r11 Lýi is' ý9r ZU LZJE rju No disaster can befall on the earth or in your souls but it is in a book before We bring it into being; that is easy for Allah. In order that you may not grieve for what has escaped you, nor be exultant at what He has given you; and Allah does not love any prideful boaster. -
Ix Ophiuchi: a High-Velocity Star Near a Molecular Cloud G
The Astronomical Journal, 130:815–824, 2005 August # 2005. The American Astronomical Society. All rights reserved. Printed in U.S.A. IX OPHIUCHI: A HIGH-VELOCITY STAR NEAR A MOLECULAR CLOUD G. H. Herbig Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 Received 2005 March 24; accepted 2005 April 26 ABSTRACT The molecular cloud Barnard 59 is probably an outlier of the Upper Sco/ Oph complex. B59 contains several T Tauri stars (TTSs), but outside its northwestern edge are three other H -emission objects whose nature has been unclear: IX, KK, and V359 Oph. This paper is a discussion of all three and of a nearby Be star (HD 154851), based largely on Keck HIRES spectrograms obtained in 2004. KK Oph is a close (1B6) double. The brighter component is an HAeBe star, and the fainter is a K-type TTS. The complex BVR variations of the unresolved pair require both components to be variable. V359 Oph is a conventional TTS. Thus, these pre-main-sequence stars continue to be recognizable as such well outside the boundary of their parent cloud. IX Oph is quite different. Its absorption spec- trum is about type G, with many peculiarities: all lines are narrow but abnormally weak, with structures that depend on ion and excitation level and that vary in detail from month to month. It could be a spectroscopic binary of small amplitude. H and H are the only prominent emission lines. They are broad, with variable central reversals. How- ever, the most unusual characteristic of IX Oph is the very high (heliocentric) radial velocity: about À310 km sÀ1, common to all spectrograms, and very different from the radial velocity of B59, about À7kmsÀ1. -
Catching up with Barnard's Star. Dave Eagle Within the Constellation Of
Catching Up with Barnard’s Star. Dave Eagle Within the constellation of Ophiuchus lies Barnard’s Star. It is a fairly faint red dwarf star of magnitude 9.53, six light years from Earth, so is fairly close to us. Its luminosity is 1/2,500th that of the Sun and 16% its mass. The diameter is estimated at about 140,000 miles, so it’s quite a small, faint star and well below naked eye visibility. So why is this star so well known? In 1916 Edward Barnard looked at a photographic plate of the area. When he compared this to a similar plate made in 1894, he noticed that one of the stars had moved between the time of the two plates being taken. Although all the stars in the sky in reality are all moving quite fast, from our remote vantage point on Earth most stars appear to appear virtually static during our lifetime as their apparent motion is extremely small. Barnard’s star, being so close and moving so fast, is one of the stars that bucks this trend. So fast indeed that it will subtend the apparent diameter equivalent to the Moon or Sun in about 176 years. So compared to other stars it is really shifting. The star is travelling at 103 miles per second and is approaching us at about 87 miles per second. In about 8,000 years it will become the closest star to us, at just under 4 light years and will have brightened to magnitude 8.6. Peter van de Camp caused great excitement in the 1960’s when he claimed to have discovered a planet (or more) around the star, due to wobbles superimposed on its movement. -
Young Super-Neptune Offers Clues to the Origin of Close-In Exoplanet 21 June 2016, by Rebecca Johnson
Young super-Neptune offers clues to the origin of close-in exoplanet 21 June 2016, by Rebecca Johnson planets in the same planetary system, or with more distant stars. These scenarios can be tested observationally by searching for young planets and studying their orbits. If the close-in population formed in place or migrated in through interactions with the natal disk, they reach their final orbital distances early on and will be found close in at young ages. In comparison, migrating a planet inward through interactions with other planets or more distant stars is effective on much longer timescales. If the latter processes dominate, planets will not be found close to their K2-33 b, shown in this illustration, is one of the youngest stars when they are young. exoplanets detected to date. It makes a complete orbit around its star in about five days. These two characteristics combined provide exciting new directions for planet-formation theories. K2-33b could have formed on a farther out orbit and quickly migrated inward. Alternatively, it could have formed in situ, or in place. Credit: NASA/JPL-Caltech A team of astronomers has confirmed the existence of a young planet, only 11 million years old, that orbits very close to its star (at 0.05 AU), with an orbital period of 5.4 days. Approximately 5 times the size of the Earth, the new planet is a "super-Neptune" and the youngest such planet This image shows the K2-33 system, and its planet known. The discovery lends unique insights into K2-33b, compared to our own solar system. -
Naming the Extrasolar Planets
Naming the extrasolar planets W. Lyra Max Planck Institute for Astronomy, K¨onigstuhl 17, 69177, Heidelberg, Germany [email protected] Abstract and OGLE-TR-182 b, which does not help educators convey the message that these planets are quite similar to Jupiter. Extrasolar planets are not named and are referred to only In stark contrast, the sentence“planet Apollo is a gas giant by their assigned scientific designation. The reason given like Jupiter” is heavily - yet invisibly - coated with Coper- by the IAU to not name the planets is that it is consid- nicanism. ered impractical as planets are expected to be common. I One reason given by the IAU for not considering naming advance some reasons as to why this logic is flawed, and sug- the extrasolar planets is that it is a task deemed impractical. gest names for the 403 extrasolar planet candidates known One source is quoted as having said “if planets are found to as of Oct 2009. The names follow a scheme of association occur very frequently in the Universe, a system of individual with the constellation that the host star pertains to, and names for planets might well rapidly be found equally im- therefore are mostly drawn from Roman-Greek mythology. practicable as it is for stars, as planet discoveries progress.” Other mythologies may also be used given that a suitable 1. This leads to a second argument. It is indeed impractical association is established. to name all stars. But some stars are named nonetheless. In fact, all other classes of astronomical bodies are named. -
A Spectroscopic Study of the Scorpio-Centaurus Association
PranllQa. Vol. 7, No.3, 1976, pp 160-\ 80. © Prmted in India. A spectroscopic study of the Scorpio-Centaurus association R RAJAMOHAN Indian Institute of Astrophysics, Bangaiore 560034 MS recehcl 5 April 1976 • I' Abstract. Rotational .... elocities as well as hydrogen and he Jlum Ine I'ntensities of .' have been one hundred. and twelve members of the Scorplo-Centaurus aSSOclatlO~ . b h derived. For stars with M~ < 0'0, the distribution of rotational velocitieS of °lt are SJlnlar the upper Scorplus subgroup and the upper Centaurus-Lupus Su b grou P 1 . I and closely resemble those of the field stars. Stars with M, > O' 0, all of w lie 1 are found in th.e dense upper Scorpius region, rotate much faster than their counter parts amongst field stars, the Pleiades and Alpha-Persei cluster members. The measured equivalent width of H'Y for 77 stars provide a distance nlOd~\U~ of 6·0±0·09 magnitudes for the association. Evolutionary effects in the del1;~e hydrogen line intensities are found between the two subgroups. The hydrogen- me intensities at all spectral types in the upper Centaurus-Lupus subgroup are systematically smaller than thOse of members in the upper Scorpius subgrouP. Analysis of high dispersion spectra of five members of the association y.ield a helium abundance of Nae(N. = 0·096 ± 0 004. Along with data available In the literature, the mean helium abundance of thirteen stars of this association is found to be 0·098 :±: O· 004 by number. For the two main subgroups of this association, we deflve a value of 0 105 ± 0 001 for the upper Centaurus-Lupus group from three stars and 0·096 ± 0·005 for the upper Scorpius group from ten stars. -
A Basic Requirement for Studying the Heavens Is Determining Where In
Abasic requirement for studying the heavens is determining where in the sky things are. To specify sky positions, astronomers have developed several coordinate systems. Each uses a coordinate grid projected on to the celestial sphere, in analogy to the geographic coordinate system used on the surface of the Earth. The coordinate systems differ only in their choice of the fundamental plane, which divides the sky into two equal hemispheres along a great circle (the fundamental plane of the geographic system is the Earth's equator) . Each coordinate system is named for its choice of fundamental plane. The equatorial coordinate system is probably the most widely used celestial coordinate system. It is also the one most closely related to the geographic coordinate system, because they use the same fun damental plane and the same poles. The projection of the Earth's equator onto the celestial sphere is called the celestial equator. Similarly, projecting the geographic poles on to the celest ial sphere defines the north and south celestial poles. However, there is an important difference between the equatorial and geographic coordinate systems: the geographic system is fixed to the Earth; it rotates as the Earth does . The equatorial system is fixed to the stars, so it appears to rotate across the sky with the stars, but of course it's really the Earth rotating under the fixed sky. The latitudinal (latitude-like) angle of the equatorial system is called declination (Dec for short) . It measures the angle of an object above or below the celestial equator. The longitud inal angle is called the right ascension (RA for short). -
Downloads/ Astero2007.Pdf) and by Aerts Et Al (2010)
This work is protected by copyright and other intellectual property rights and duplication or sale of all or part is not permitted, except that material may be duplicated by you for research, private study, criticism/review or educational purposes. Electronic or print copies are for your own personal, non- commercial use and shall not be passed to any other individual. No quotation may be published without proper acknowledgement. For any other use, or to quote extensively from the work, permission must be obtained from the copyright holder/s. i Fundamental Properties of Solar-Type Eclipsing Binary Stars, and Kinematic Biases of Exoplanet Host Stars Richard J. Hutcheon Submitted in accordance with the requirements for the degree of Doctor of Philosophy. Research Institute: School of Environmental and Physical Sciences and Applied Mathematics. University of Keele June 2015 ii iii Abstract This thesis is in three parts: 1) a kinematical study of exoplanet host stars, 2) a study of the detached eclipsing binary V1094 Tau and 3) and observations of other eclipsing binaries. Part I investigates kinematical biases between two methods of detecting exoplanets; the ground based transit and radial velocity methods. Distances of the host stars from each method lie in almost non-overlapping groups. Samples of host stars from each group are selected. They are compared by means of matching comparison samples of stars not known to have exoplanets. The detection methods are found to introduce a negligible bias into the metallicities of the host stars but the ground based transit method introduces a median age bias of about -2 Gyr. -
Stellar Evolution
AccessScience from McGraw-Hill Education Page 1 of 19 www.accessscience.com Stellar evolution Contributed by: James B. Kaler Publication year: 2014 The large-scale, systematic, and irreversible changes over time of the structure and composition of a star. Types of stars Dozens of different types of stars populate the Milky Way Galaxy. The most common are main-sequence dwarfs like the Sun that fuse hydrogen into helium within their cores (the core of the Sun occupies about half its mass). Dwarfs run the full gamut of stellar masses, from perhaps as much as 200 solar masses (200 M,⊙) down to the minimum of 0.075 solar mass (beneath which the full proton-proton chain does not operate). They occupy the spectral sequence from class O (maximum effective temperature nearly 50,000 K or 90,000◦F, maximum luminosity 5 × 10,6 solar), through classes B, A, F, G, K, and M, to the new class L (2400 K or 3860◦F and under, typical luminosity below 10,−4 solar). Within the main sequence, they break into two broad groups, those under 1.3 solar masses (class F5), whose luminosities derive from the proton-proton chain, and higher-mass stars that are supported principally by the carbon cycle. Below the end of the main sequence (masses less than 0.075 M,⊙) lie the brown dwarfs that occupy half of class L and all of class T (the latter under 1400 K or 2060◦F). These shine both from gravitational energy and from fusion of their natural deuterium. Their low-mass limit is unknown.