DOCSLIB.ORG

Dissertation Submitted to The

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dissertation Submitted to The Dissertation submitted to the Combined Faculties of the Natural Sciences and Mathematics of the Ruperto-Carola-University of Heidelberg, Germany for the degree of Doctor of Natural Science Put forward by Diplom-Physikerin Eva Meyer born in: Essen, Germany Oral Examination: 21st July 2010 High Precision Astrometry with Adaptive Optics aided Imaging Referees: Prof. Dr. Hans-Walter Rix Prof. Dr. Joachim Wambsganß Abstract Currently more than 450 exoplanets are known and this number increases nearly every day. Only a few constraints on their orbital parameters and physical characteristics can be determined, as most exoplanets are detected indirectly and one should therefore refer to them as exoplanet candidates. Measuring the astrometric signal of a planet or low mass companion by means of measuring the wobble of the host star yields the full set of orbital parameters. With this information the true masses of the planet candidates can be determined, making it possible to establish the candidates as real exoplanets, brown dwarfs or low mass stars. In the context of this thesis, an M-dwarf star with a brown dwarf candidate companion, discovered by radial velocity measurements, was observed within an astrometric monitoring program to detect the astrometric signal. Ground based adaptive optics aided imaging with the ESO/NACO instrument was used with the aim to establish its true nature (brown dwarf vs. star) and to investigate the prospects of this technique for exoplanet detection. The astrometric corrections necessary to perform high precision astrometry are described and their contribution to the overall precision is investigated. Due to large uncertainties in the pixel-scale and the orientation of the detector, no detection of the astrometric orbit signal was possible. The image quality of ground-based telescopes is limited by the turbulence in Earth’s at- mosphere. The induced distortions of the light can be measured and corrected with the adaptive optics technique and nearly diffraction limited performance can be achieved. However, the correction is only useful within a small angle around the guide star in single guide star measurements. The novel correction technique of multi conjugated adaptive optics uses several guide stars to correct a larger field of view. The VLT/MAD instrument was built to demonstrate this technique. Observations with MAD are an- alyzed in terms of astrometric precision in this work. Two sets of data are compared, which were obtained in different correction modes: pure ground layer correction and full multi conjugated correction. i Zusammenfassung Mehr als 450 extrasolare Planeten sind zurzeit bekannt und diese Zahl wird fast t¨aglich gr¨osser.Da die meisten Exoplaneten indirekt entdeckt werden, k¨onnennur wenige Ein- schr¨ankungenbez¨uglich ihrer Bahnparameter und physikalischen Eigenschaften gemacht werden und sie sollten daher vorl¨aufigals Exoplanet-Kandidaten bezeichnet werden. Misst man das astrometrische Signal eines planetaren oder massearmen Begleiters, indem man die Reflexbewegung des Hauptsterns vermisst, so erh¨altman den vollen Satz an orbitalen Parametern. Mit dieser Information kann die genaue Masse der Kandidaten bestimmt werden und es ist somit m¨oglich, die Planetenkandidaten als wahre Exoplaneten, Braune Zwerge oder massearme Sterne einzustufen. Im Rahmen der vorliegenden Doktorarbeit wurde ein Zwergstern der Spektralklasse M, der einen mittels Radialgeschwindigkeitsmessungen entdeckten wahrscheinlichen Braunen Zwerg als Begleiter hat, innerhalb eines fortlaufenden Beobachtungsprogramms zur Detektion des astrometrischen Signals beobachtet. Bodengebundene Beobachtungen mit dem Adaptiven Optik (AO) Instrument ESO/NACO wurden durchgef¨uhrt,um die wahre Natur des Begleiters zu bestimmen (Brauner Zwerg oder massearmer Stern) und die Aussichten dieser Technik im Bereich der Planetenendeckung zu untersuchen. Die astrometrischen Korrekturen, notwendig um hochpr¨aziseAstrometrie zu betreiben, werden in diesem Zusammenhang beschrieben und ihr Beitrag zur Gesamtmessge- nauigkeit untersucht. Die großen Unsicherheiten in der Messgenauigkeit der Anderung¨ der Pixel-Skala und der Ausrichtung des Detektors verhinderten jedoch, das Signal des astrometrischen Orbits zu messen. Die Abbildungsqualit¨ateines bodengebundenen Teleskopes ist begrenzt durch die Tur- bulenz in der Atmosph¨areder Erde. Die dadurch hervorgerufenenen Verformungen der Lichtwellen k¨onnenmit Hilfe der Technik der Adaptiven Optik vermessen und kor- rigiert werden und somit beinahe beugungsbegrenzte Abbildungen erzeugt werden. Im Fall der klassischen AO mit nur einem Referenzstern ist die Korrektur jedoch nur in einem engen Bereich um den Referenzstern m¨oglich. Multikonjugierte Adaptive Op- tik verwendet mehrere Referenzsterne, um ein gr¨osseresGesichtfeld zu korrigieren. Das MAD Instrument wurde gebaut und am Very Large Telescope installiert, um diese neue Technik zu demonstrieren. Beobachtungen mit MAD wurden im Rahmen dieser Arbeit auf ihre astrometrische Genauigkeit hin ausgewertet. Dabei wurden zwei Datens¨atze verglichen, die in unterschiedlichen Korrektur-Modi aufgenommen wurden: zum einen wurde nur die Turbulenzschicht nahe am Boden korrigiert, zum anderen die volle mul- tikonjugierte Konfiguration des Instrumentes genutzt. ii for my father in loving memory iii iv Contents 1 Introduction 1 1.1 Orbital Elements . 3 1.2 Detection Methods . 4 1.2.1 Pulsar Timing . 4 1.2.2 Radial Velocity Measurements . 4 1.2.3 Transits . 6 1.2.4 Gravitational Microlensing . 8 1.2.5 Direct Imaging . 8 1.2.6 Astrometry . 11 1.3 Brown Dwarfs . 15 1.3.1 Brown Dwarf Formation Processes . 17 1.3.2 The Brown Dwarf Desert . 17 1.4 Goal of this Work . 18 2 Introduction to Adaptive Optics 21 2.1 Atmospheric Turbulence . 23 2.1.1 Fried-Parameter . 25 2.1.2 Time Dependent Effects . 25 2.2 Principles of Adaptive Optics . 25 2.2.1 General Setup of an AO System . 26 2.2.2 Strehl Ratio . 27 2.2.3 Anisoplanatism . 27 2.3 NACO . 28 2.3.1 Our Observation Configuration . 30 v 3 Observations and Data Reduction 31 3.1 The Target Field . 31 3.2 The Reference Field . 33 3.3 Adaptive Optics Observations of GJ 1046 . 35 3.4 Data Reduction . 38 3.4.1 Sky Subtraction . 39 3.4.2 50 Hz Noise . 40 3.4.3 Shift and Add . 40 4 Analysis and Astrometric Corrections 41 4.1 Position Measurements . 41 4.1.1 Positional Error Estimate - Bootstrapping . 43 4.2 Astrometry with FITS-Header Keywords . 43 4.2.1 World Coordinates in FITS . 43 4.2.2 Celestial Coordinates in FITS . 46 4.2.3 Transformation from xy-Coordinates into RA/DEC . 46 4.3 Astrometric Corrections . 47 4.3.1 Theory of Atmospheric Refraction . 47 4.3.2 Differential Atmospheric Refraction . 50 4.3.3 Correction for Differential Refraction . 51 4.3.4 Errors from Differential Refraction Correction . 55 4.3.5 Theory of Aberration . 56 4.3.6 Correction for Differential Aberration . 59 4.3.7 Errors from Differential Aberration Correction . 60 4.3.8 Light Time Delay . 60 4.3.9 Differential Tilt Jitter . 61 4.3.10 Parallax . 62 4.3.11 Proper Motion . 64 4.4 Plate-scale and Detector Rotation Stability . 66 4.4.1 Plate-scale Correction . 69 5 The Orbit Fit 73 vi 5.1 Preparing the Coordinates for the Orbital Fit . 73 5.2 Theory of Deriving the Orbital Elements . 76 5.2.1 The Thiele-Innes Constants . 77 5.3 The Astrometric Orbit Fit . 79 6 Results 83 6.1 The Orbit . 83 6.2 Discussion and Conclusion . 86 7 Introduction to MCAO and MAD 91 7.1 MCAO - The Next Generation of Adaptive Optics . 91 7.1.1 Star Oriented Approach . 92 7.1.2 Layer Oriented Approach . 92 7.1.3 Ground Layer Adaptive Optics . 93 7.1.4 Current and Future MCAO Systems . 93 7.2 MAD - Multi conjugated Adaptive optics Demonstrator . 94 7.3 Goal of this Work . 96 8 Astrometry with MAD 97 8.1 Observations . 97 8.1.1 GLAO - 47 Tuc . 97 8.1.2 MCAO - NGC 6388 . 99 8.2 Data Reduction . 100 8.3 Strehl Maps . 104 8.4 PSF Tests . 107 8.5 Position Measurements . 112 8.6 Ensquared Energy . 114 8.7 Distortion Mapping . 115 9 Results 117 9.1 Separation Measurements . 118 9.2 Residual Mapping . 120 9.3 Mean Positions . 123 vii 9.4 Discussion and Conclusion . 126 A Strehl plots 129 B Acronyms 137 Bibliography 148 viii List of Figures 1.1 Definition of the orbital elements. 3 1.2 Radial velocity curve of the system HD 209458 . 6 1.3 Transit light curves for the planetary system HD 209458 . 7 1.4 Light curve of a gravitational lensing event of a star with a planet . 9 1.5 Image of the three planetary companions to the star HR 8799 . 10 1.6 Examples of astrometric motions of stars due to planets . 13 1.7 Brown dwarf desert in mass and period . 19 2.1 The Point-Spread-Function (PSF) of a point source . 22 2.2 Effect of atmospheric turbulence on the image of a star . 23 2.3 Structure of the atmosphere with typical turbulence profile. (Hardy, 1998) 24 2.4 Principle setup of an AO system. 26 2.5 Angular Anisoplanatism . 28 3.1 RV time series of GJ 1046 . 33 3.2 Time series of the movement of GJ 1046 on the sky . 34 3.3 NACO image of GJ 1046 and the reference field in the globular cluster 47 Tucanae from July 2008. 35 3.4 GJ 1046 observations overplotted over a simulated orbit . 37 3.5 Jitter pattern for the target and reference field . 39 4.1 Stepwise description of the corrections applied to the measures pixel coordinates of the stars. 42 4.2 Conversion of pixel coordinates to world coordinates (after Calabretta and Greisen (2002)). 45 4.3 Refraction in the atmosphere. For more details see text. 48 4.4 Differential refraction . 52 ix 4.5 Sign of the differential refraction correction during different times of observations . 54 4.6 Stellar aberration . ..
Load more

Recommended publications
  • EMBEDDED CLUSTERS in the LARGE MAGELLANIC CLOUD by Krista Romita Grocholski August 2017 Chair: Elizabeth A
    EMBEDDED CLUSTERS IN THE LARGE MAGELLANIC CLOUD By KRISTA ROMITA GROCHOLSKI A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2017 c 2017 Krista Romita Grocholski To- Aaron, Allegra, Mom, and Dad. All is possible with you at my side. Thank you. ACKNOWLEDGMENTS First, I would like to acknowledge the University of Florida Astronomy Department for providing me with the opportunity to complete my dissertation. I would like to thank Dr. Elizabeth Lada for taking me on as her graduate student, and for giving me the opportunity and freedom to become a confident, independent researcher. I would also like to thank Drs. Ata Sarajadini, Anthony Gonzalez, and Alessandro Forte for serving on my committee. I would like to give special thanks to Dr. Maria-Rosa Cioni; without your generous collaboration this dissertation project would not be possible. Drs. Margaret Meixner and Lynn Carlson deserve considerable credit for getting me started, not only in astronomy research, but in the wonderful field of star formation in the Large Magellanic Cloud. I will always be grateful for your support and friendship over the years. I would also like to acknowledge Dr. Igor Mikolic-Torreira for giving me the opportunity to apply my research skills beyond the realm of academia. Your guidance and enthusiastic support opened doors to me that changed the nature of my career. I cannot thank you enough. To my fellow UF Astronomy graduate students, the community you have created is something I am proud to have been a part of.
    [Show full text]
  • In the Heart of the Orion Nebula 2 April 2009
    In the heart of the Orion Nebula 2 April 2009 technique allows astronomers to combine the light from several telescopes, forming a huge virtual telescope with a resolving power corresponding to that of a single telescope with 200 m diameter. The Very Large Telescope Interferometer (VLTI) now offers this revolutionary technique to European astronomers and allows them to directly reconstruct images from the interferometric infrared data. A team of European astronomers utilized the VLTI and its near-infrared beam-combination instrument AMBER to demonstrate the imaging capabilities of this unique facility and to study the intriguing Zooming in the centre of the Orion star-forming region massive young star Theta1 Ori C in unprecedented with the four bright Trapezium stars (Theta 1 Ori A-D). detail. The dominant star is Theta 1 Ori C, which was imaged with unprecedented resolution with the VLT Theta 1 Ori C is the dominant and most luminous interferometer (lower right). Image: MPIfR/Stefan Kraus, star in the Orion star-forming region. Located at a ESO and NASA/Chris O'Dell distance of only about 1300 light years, it is the nearest region where massive stars are born and provides a unique laboratory to study the formation process of high-mass stars in detail. The intense (PhysOrg.com) -- A team of astronomers, led by radiation of Theta 1 Ori C is ionizing the whole Stefan Kraus and Gerd Weigelt from the Max- Orion nebula. With its strong wind, the star also Planck-Institute for Radio Astronomy (MPIfR) in shapes the famous Orion proplyds, young stars still Bonn, used ESO's Very Large telescope surrounded by their protoplanetary dust disks.
    [Show full text]
  • Software for Aerospace Educationa Bibliography (Second Edition)
    DOCUMENT RESUME ED 312 134 SE 050 904 AUTHOR Vogt, Gregory L.; And Others TITLE Software for Aerospace EducationA Bibliography (Second Edition). INSTITUTION National Aeronautics and Space Administration, Washington, DC. Education Technology Branch. REPORT NO NASA-PED-106 PUB DATE 89 NOTE 91p. PUB TYPE plok/Product Reviews (072) -- Reference Materials - Bibliographies (131) EDRS PRICE MF01/PC04 Plus Postage. DESCRIPTORS *Aerospace Education; Astronomy; *Computer Software; *Computer Software Reviews; *Databases; Elementary School Science; Elementary Secondary Education; Engineering Education; Satellites (Aerospace); Science Fiction; Science Materials; Secondary School Science; *Videodisks IDENTIFIERS National Aeronautics and Space Administration ABSTRACT The software described in this bibliography represents programs made available to the National Aeronautics and Space Administration (NASA) Educational Technology Branch by software producers and vendors. More than 200 computer software programs and 12 laser videodisk programs are reviewed in terms of title, copyright, subject, application, type, grade level, minimum system requir3ments, description, components, features, producer, vendor, and cost. Subject areas covered include: (1) aeronautics; (2) aerospace physics; (3) astronomy; (4) manned space exploration; (5) rocketry; (6) satellites; and (7) science fiction. The last section describes how to use the NASA SpaceLink which is a 24-hour computer information database developed to serve teachers and other educators. Lists of vendors and NASA Teacher Resource Centers are appended. (YP) Reproductions supplied by EDRS are the best that can be made from the original document. Mr sr. O4 i< t E r° 0 2 I. .14l v r3E 51 B `g fh g gc .2- to ch. s 0 ''' t I .1 tacciu'i .cg2; o < 3. f.
    [Show full text]
  • Galactic Center: an Improved Astrometric Reference Frame for Stellar Orbits Around the Supermassive Black Hole Shoko Sakai,1 Jessica R
    Draft version January 28, 2019 Typeset using LATEX twocolumn style in AASTeX62 The Galactic Center: An Improved Astrometric Reference Frame for Stellar Orbits around the Supermassive Black Hole Shoko Sakai,1 Jessica R. Lu,2 Andrea Ghez,1 Siyao Jia,2 Tuan Do,1 Gunther Witzel,1 Abhimat K. Gautam,1 Aurelien Hees,3, 1 E. Becklin,1 K. Matthews,4 and M. W. Hosek Jr.5 1UCLA Department of Physics and Astronomy, Los Angeles, CA 90095-1547, USA 2Astronomy Department, University of California, Berkeley, CA 94720, USA 3SYRTE, Observatoire de Paris, Universit´ePSL, CNRS, Sorbonne Universit´e,LNE, 61 avenue de l’Observatoire 75014 Paris 4Astrophysics, California Institute of Technology, MC 249-17, Pasadena, CA 91125, USA 5Institute for Astronomy, University of Hawaii, Honolulu, HI 96822, USA (Received; Revised; Accepted) Submitted to ApJ ABSTRACT Precision measurements of the stars in short-period orbits around the supermassive black hole at the Galactic Center are now being used to constrain general relativistic effects, such as the gravitational redshift and periapse precession. One of the largest systematic uncertainties in the measured orbits has been errors in the astrometric reference frame, which is derived from seven infrared-bright stars associated with SiO masers that have extremely accurate radio positions, measured in the Sgr A*-rest frame. We have improved the astrometric reference frame within 1400 of the Galactic Center by a factor of 2.5 in position and a factor of 5 in proper motion. In the new reference frame, Sgr A* is localized to within a position of 0.645 mas and proper motion of 0.03 mas yr−1.
    [Show full text]
  • 00E the Construction of the Universe Symphony
    The basic construction of the Universe Symphony. There are 30 asterisms (Suites) in the Universe Symphony. I divided the asterisms into 15 groups. The asterisms in the same group, lay close to each other. Asterisms!! in Constellation!Stars!Objects nearby 01 The W!!!Cassiopeia!!Segin !!!!!!!Ruchbah !!!!!!!Marj !!!!!!!Schedar !!!!!!!Caph !!!!!!!!!Sailboat Cluster !!!!!!!!!Gamma Cassiopeia Nebula !!!!!!!!!NGC 129 !!!!!!!!!M 103 !!!!!!!!!NGC 637 !!!!!!!!!NGC 654 !!!!!!!!!NGC 659 !!!!!!!!!PacMan Nebula !!!!!!!!!Owl Cluster !!!!!!!!!NGC 663 Asterisms!! in Constellation!Stars!!Objects nearby 02 Northern Fly!!Aries!!!41 Arietis !!!!!!!39 Arietis!!! !!!!!!!35 Arietis !!!!!!!!!!NGC 1056 02 Whale’s Head!!Cetus!! ! Menkar !!!!!!!Lambda Ceti! !!!!!!!Mu Ceti !!!!!!!Xi2 Ceti !!!!!!!Kaffalijidhma !!!!!!!!!!IC 302 !!!!!!!!!!NGC 990 !!!!!!!!!!NGC 1024 !!!!!!!!!!NGC 1026 !!!!!!!!!!NGC 1070 !!!!!!!!!!NGC 1085 !!!!!!!!!!NGC 1107 !!!!!!!!!!NGC 1137 !!!!!!!!!!NGC 1143 !!!!!!!!!!NGC 1144 !!!!!!!!!!NGC 1153 Asterisms!! in Constellation Stars!!Objects nearby 03 Hyades!!!Taurus! Aldebaran !!!!!! Theta 2 Tauri !!!!!! Gamma Tauri !!!!!! Delta 1 Tauri !!!!!! Epsilon Tauri !!!!!!!!!Struve’s Lost Nebula !!!!!!!!!Hind’s Variable Nebula !!!!!!!!!IC 374 03 Kids!!!Auriga! Almaaz !!!!!! Hoedus II !!!!!! Hoedus I !!!!!!!!!The Kite Cluster !!!!!!!!!IC 397 03 Pleiades!! ! Taurus! Pleione (Seven Sisters)!! ! ! Atlas !!!!!! Alcyone !!!!!! Merope !!!!!! Electra !!!!!! Celaeno !!!!!! Taygeta !!!!!! Asterope !!!!!! Maia !!!!!!!!!Maia Nebula !!!!!!!!!Merope Nebula !!!!!!!!!Merope
    [Show full text]
  • Visual/Infrared Interferometry of Orion Trapezium Stars: Preliminary Dynamical Orbit and Aperture Synthesis Imaging of the Θ1 Orionis C System
    A&A 466, 649–659 (2007) Astronomy DOI: 10.1051/0004-6361:20066965 & c ESO 2007 Astrophysics Visual/infrared interferometry of Orion Trapezium stars: preliminary dynamical orbit and aperture synthesis imaging of the θ1 Orionis C system S. Kraus1, Y. Y. Balega2, J.-P. Berger3, K.-H. Hofmann1, R. Millan-Gabet4, J. D. Monnier5, K. Ohnaka1, E. Pedretti5, Th. Preibisch1, D. Schertl1, F. P. Schloerb6, W. A. Traub7, and G. Weigelt1 1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: [email protected] 2 Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnij Arkhyz, Zelenchuk region, Karachai-Cherkesia 357147, Russia 3 Laboratoire d’Astrophysique de Grenoble, UMR 5571 Université Joseph Fourier/CNRS, BP 53, 38041 Grenoble Cedex 9, France 4 Michelson Science Center, California Institute of Technology, Pasadena, CA 91125, USA 5 Astronomy Department, University of Michigan, 500 Church Street, Ann Arbor, MI 48104, USA 6 Department of Astronomy, University of Massachusetts, LGRT-B 619E, 710 North Pleasant Street, Amherst, MA 01003, USA 7 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02183, USA Received 19 December 2006 / Accepted 7 February 2007 ABSTRACT Context. Located in the Orion Trapezium cluster, θ1Ori C is one of the youngest and nearest high-mass stars (O5-O7) known. Besides its unique properties as a magnetic rotator, the system is also known to be a close binary. Aims. By tracing its orbital motion, we aim to determine the orbit and dynamical mass of the system, yielding a characterization of the individual components and, ultimately, also new constraints for stellar evolution models in the high-mass regime.
    [Show full text]
  • Cosmic Raw Material Fig 20-CO, P.438
    Stars form in greatStars clouds form of gas in and great dust clouds of gas and dust Slide 1 Cosmic raw material Fig 20-CO, p.438 Chapter Opener The Eagle Nebula (M16) Stars form in great clouds of gas and dust, and this image shows a large region of such cosmic raw material. The gas is visible because, about 2 million years ago, the cloud produced a cluster of bright stars, whose light ionizes the hydrogen gas nearby, causing it to glow. The cluster can be seen just above and to the left of the darker columns of dust at the center of the image. The dark columns or “elephant trunks” of material are seen in much more detail in Figures 20.1 and 20.2. This false-color image was created by combining images taken through filters that select lines of hydrogen alpha (green), oxygen (blue), and sulfur (red). (T.A. Rector, B.A. Wolpa, and OAO/NRAO/AURA/NSF) 1 The Central Region of the Orion Nebula Slide 2 Fig 20-5a, p.443 Figure 20.5 The Central Region of the Orion Nebula The Orion Nebula harbors some of the youngest stars in the solar neighborhood. At the heart of the nebula is the Trapezium cluster, which includes four very bright stars that provide much of the energy that causes the nebula to glow so brightly. In these images, we see a section of the nebula in visible light (left) and infrared (right). The four bright stars in the center of the visible-light image are the Trapezium stars.
    [Show full text]
  • Tracing the Young Massive High-Eccentricity Binary System Θ1orionis C Through Periastron Passage
    A&A 497, 195–207 (2009) Astronomy DOI: 10.1051/0004-6361/200810368 & c ESO 2009 Astrophysics Tracing the young massive high-eccentricity binary system θ1Orionis C through periastron passage S. Kraus1,G.Weigelt1,Y.Y.Balega2, J. A. Docobo3, K.-H. Hofmann1, T. Preibisch4, D. Schertl1, V. S. Tamazian3, T. Driebe1, K. Ohnaka1,R.Petrov5,M.Schöller6, and M. Smith7 1 Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, 53121 Bonn, Germany e-mail: [email protected] 2 Special Astrophysical Observatory, Russian Academy of Sciences, Nizhnij Arkhyz, Zelenchuk region, Karachai-Cherkesia 357147, Russia 3 Astronomical Observatory R. M. Aller, University of Santiago de Compostela, Galicia, Spain 4 Universitäts-Sternwarte München, Scheinerstr. 1, 81679 München, Germany 5 Laboratoire Universitaire d’Astrophysique de Nice, UMR 6525 Université de Nice/CNRS, Parc Valrose, 06108 Nice Cedex 2, France 6 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748 Garching, Germany 7 Centre for Astrophysics & Planetary Science, University of Kent, Canterbury CT2 7NH, UK Received 11 June 2008 / Accepted 27 January 2009 ABSTRACT Context. The nearby high-mass star binary system θ1Ori C is the brightest and most massive of the Trapezium OB stars at the core of the Orion Nebula Cluster, and it represents a perfect laboratory to determine the fundamental parameters of young hot stars and to constrain the distance of the Orion Trapezium Cluster. Aims. By tracing the orbital motion of the θ1Ori C components, we aim to refine the dynamical orbit of this important binary system. Methods. Between January 2007 and March 2008, we observed θ1Ori C with VLTI/AMBER near-infrared (H-andK-band) long- baseline interferometry, as well as with bispectrum speckle interferometry with the ESO 3.6 m and the BTA 6 m telescopes (B- and V-band).
    [Show full text]
  • Culpeper Astronomy Club Meeting November 25, 2019 Overview
    The Winter Constellations Culpeper Astronomy Club Meeting November 25, 2019 Overview • Introductions • Special Topics • Video: The Winter Constellations • Constellations: Orion, Canis Minor, Eridanus • Observing Session Special Topic #1: Mercury Transit (11 Nov) • Observing Session – 0730-1306 • Morning Calm Observatory • 5 Members participating • Trees obscured early viewing • Scattered Clouds throughout • Equipment: • Stellarvue SV110ED • Stellarvue SV102ED • Meade 12” LX200 • All full aperture filters • Observed most of the transit and the final egress • Bonus: Caught a couple of airliners crossing the Sun Venus Transit – 2012 Special Topic #2: VIPER to the Moon • NASA is sending a mobile robot to the south pole of the Moon: • Get a close-up view of the location and concentration of water ice in the region • Sample the water ice at the same pole where the first woman and next man will land in 2024 under the Artemis program • About the size of a golf cart, the Volatiles Investigating Polar Exploration Rover, or VIPER, will roam several miles • Four science instruments — including a 1- meter drill — to sample various soil environments. • Planned for delivery in December 2022, VIPER will collect about 100 days of data that will be used to inform development of the first global water resource maps of the Moon Special Topic #3: Going Back to Pluto? • As currently envisioned, the orbiter would cruise around the Pluto system, using gravity assists from the dwarf planet's largest moon, Charon, to slingshot it here and there • First, limited
    [Show full text]
  • What's up This Month – February 2021 These Pages Are Intended to Help You Find Your Way Around the Sky
    WHAT'S UP THIS MONTH – FEBRUARY 2021 THESE PAGES ARE INTENDED TO HELP YOU FIND YOUR WAY AROUND THE SKY The chart above shows the whole night sky as it appears on 15th February at 21:00 (9 o’clock) Greenwich Mean Time (GMT). As the Earth orbits the Sun and we look out into space each night the stars will appear to have moved across the sky by a small amount. Every month Earth moves one twelfth of its circuit around the Sun, this amounts to 30 degrees each month. There are about 30 days in each month so each night the stars appear to move about 1 degree. The sky will therefore appear the same as shown on the chart above at 8 o’clock GMT at the beginning of the month and at 10 o’clock GMT at the end of the month. The stars also appear to move 15º (360º divided by 24) each hour from east to west, due to the Earth rotating once every 24 hours. The centre of the chart will be the position in the sky directly overhead, called the Zenith. First we need to find some familiar objects so we can get our bearings. The Pole Star Polaris can be easily found by first finding the familiar shape of the Great Bear ‘Ursa Major’ that is also sometimes called the Plough or even the Big Dipper by the Americans. Ursa Major is visible throughout the year from Britain and is always quite easy to find. This month it is in the North 1 of 15 pages East.
    [Show full text]
  • Variable Star Section Circular
    British Astronomical Association VARIABLE STAR SECTION CIRCULAR No 90, December 1996 Contents A Selection of Light Curves ............................................................................. 1 General News ................................................................................................... 2 Recurrent Objects Programme News ............................................................... 3 Chart News ....................................................................................................... 4 Binocular Priority Stars in 1995 ...................................................................... 5 Asteroid-Variable Appulses: a short list to 2000 ........................................... 10 Comments on the VSS Observers Questionnaire .......................................... 12 VSS Meeting: part 1....................................................................................... 14 Photoelectric Minima of Eclipsing Binaries 1995 ......................................... 16 Recent Papers on Variable Stars .................................................................... 17 IBVS............................................................................................................... 18 Eclipsing Binary Predictions .......................................................................... 19 New Chart for CH Cyg................................................................................... 22 ISSN 0267-9272 Office: Burlington House, Piccadilly, London, W1V 9AG A SELECTION OF LIGHT CURVES
    [Show full text]
  • The Nuclear Star Cluster of the Milky Way: Proper Motions and Mass R
    Rochester Institute of Technology RIT Scholar Works Articles 3-5-2009 The ucleN ar Star Cluster of the Milky Way: Proper Motions and Mass Rainer Schödel Instituto de Astrofísica de Andalucía David Merritt Rochester Institute of Technology Andreas Eckart Universität zu Köln Follow this and additional works at: http://scholarworks.rit.edu/article Recommended Citation The uclen ar star cluster of the Milky Way: proper motions and mass R. Schödel, D. Merritt nda A. Eckart A&A, 502 1 (2009) 91-111 DOI: https://doi.org/10.1051/0004-6361/200810922 This Article is brought to you for free and open access by RIT Scholar Works. It has been accepted for inclusion in Articles by an authorized administrator of RIT Scholar Works. For more information, please contact [email protected]. Astronomy & Astrophysics manuscript no. proper c ESO 2009 February 23, 2009 The nuclear star cluster of the Milky Way: Proper motions and mass R. Schodel¨ 1, D. Merritt2, and A. Eckart3 1 Instituto de Astrof´ısica de Andaluc´ıa (IAA) - CSIC, Camino Bajo de Huetor´ 50, E-18008 Granada, Spain e-mail: [email protected] 2 Department of Physics and Center for Computational Relativity and Gravitation, Rochester Institute of Technology, Rochester, NY 14623, USA e-mail: [email protected] 3 I.Physikalisches Institut, Universitat¨ zu Koln,¨ Zulpicher¨ Str.77, 50937 Koln,¨ Germany e-mail: [email protected] ABSTRACT Context. Nuclear star clusters (NSCs) are located at the photometric and dynamical centers of the majority of galaxies. They are among the densest star clusters in the Universe. The NSC in the Milky Way is the only object of this class that can be resolved into individual stars.
    [Show full text]