A New Measurement of the Hubble Constant and Matter Content of the Universe Using Extragalactic Background Light Γ-Ray Attenuation
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The Kinematic Signature of the Galactic Warp in Gaia DR1-I. the Hipparcos Subsample
Astronomy & Astrophysics manuscript no. WarpGaia c ESO 2021 September 26, 2021 The kinematic signature of the Galactic warp in Gaia DR1 I. The Hipparcos sub-sample E. Poggio1; 2, R. Drimmel2, R. L. Smart2; 3, A. Spagna2, and M. G. Lattanzi2 1 Università di Torino, Dipartimento di Fisica, via P. Giuria 1, 10125 Torino, Italy 2 Osservatorio Astrofisico di Torino, Istituto Nazionale di Astrofisica (INAF), Strada Osservatorio 20, 10025 Pino Torinese, Italy 3 School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB, UK ABSTRACT Context. The mechanism responsible for the warp of our Galaxy, as well as its dynamical nature, continues to remain unknown. With the advent of high precision astrometry, new horizons have been opened for detecting the kinematics associated with the warp and constraining possible warp formation scenarios for the Milky Way. Aims. The aim of this contribution is to establish whether the first Gaia data release (DR1) shows significant evidence of the kinematic signature expected from a long-lived Galactic warp in the kinematics of distant OB stars. As the first paper in a series, we present our approach for analyzing the proper motions and apply it to the sub-sample of Hipparcos stars. Methods. We select a sample of 989 distant spectroscopically-identified OB stars from the New Reduction of Hipparcos (van Leeuwen 2008), of which 758 are also in the first Gaia data release (DR1), covering distances from 0.5 to 3 kpc from the Sun. We develop a model of the spatial distribution and kinematics of the OB stars from which we produce the probability distribution functions of the proper motions, with and without the systematic motions expected from a long-lived warp. -
Sky-High 2009
Sky-High 2009 Total Solar Eclipse, 29th March 2006 The 17th annual guide to astronomical phenomena visible from Ireland during the year ahead (naked-eye, binocular and beyond) By John O’Neill and Liam Smyth Published by the Irish Astronomical Society € 5 P.O. Box 2547, Dublin 14, Ireland. e-mail: [email protected] www.irishastrosoc.org Page 1 Foreword Contents 3 Your Night Sky Primer We send greetings to all fellow astronomers and welcome them to this, the seventeenth edition of 5 Sky Diary 2009 Sky-High. 8 Phases of Moon; Sunrise and Sunset in 2009 We thank the following contributors for their 9 The Planets in 2009 articles: Patricia Carroll, John Flannery and James O’Connor. The remaining material was written by 12 Eclipses in 2009 the editors John O’Neill and Liam Smyth. The Gal- 14 Comets in 2009 lery has images and drawings by Society members. The times of sunrise etc. are from SUNRISE by J. 16 Meteors Showers in 2009 O’Neill. 17 Asteroids in 2009 We are always glad to hear what you liked, or 18 Variable Stars in 2009 what you would like to have included in Sky-High. If we have slipped up on any matter of fact, let us 19 A Brief Trip Southwards know. We can put a correction in future issues. And if you have any problem with understanding 20 Deciphering Star Names the contents or would like more information on 22 Epsilon Aurigae – a long period variable any topic, feel free to contact us at the Society e- mail address [email protected]. -
October 2015 BRAS Newsletter
October, 2015 Next Meeting: Monday, Oct. 12th at 7pm at the HRPO Lunar Eclipse on Sept 27th, 2015. Image by BRAS member David Leadingham, one of the few that got a clear view for a couple of minutes through the clouds in our area! Click on the pic for more info on upcoming eclipses What's In This Issue? President's Message AstroShort: Simulating the Universe Secretary's Summary of Sept. Meeting Message From the HRPO Recent BRAS Forum Entries 20/20 Vision Campaign Observing Notes by John Nagle (He's Back!) President's Message “Astronomy is useful because it raises us above ourselves; it is useful because it is grand. It shows us how small is man’s body, how great his mind, since his intelligence can embrace the whole of this dazzling immensity, where his body is only an obscure point, and enjoy its silent harmony." – Henri Poincare, 19th Century mathematician and physicist We all have our reasons for being involved in astronomy. That quote elegantly expresses just one man’s thoughts. What attracted you to astronomy? What do you tell people who ask? I think we all have experienced some indefinable draw to the night sky and the wonders of the universe. Maybe that is it. Wonder. At least for me it is. Wonder, beauty, harmony, perspective. Where does it end? Think about those things and let me know if you have something about that you would like to say at our next meeting. Alternately, you could write up something for this newsletter. Well the total lunar eclipse certainly was a washout. -
Variable Star Section Circular
British Astronomical Association VARIABLE STAR SECTION CIRCULAR No 112, June 2002 Contents Light Curves for some Eclipsing Binary Stars .............................. inside covers From the Director ............................................................................................. 1 Change in E-mail Address for Computer Secretary ......................................... 1 Letters ............................................................................................................... 2 Information on Photometry Available .............................................................. 2 Change to September Circular Deadline .......................................................... 2 The Fade of UY Cen ........................................................................................ 3 Meauring Times of Minimum of EBs using a CCD camera ............................ 4 Photometric Calibration of an MX516 CCD Camera ...................................... 7 Recent Papers on Variable Stars .................................................................... 14 IBVS............................................................................................................... 15 Eclipsing Binary Predictions .......................................................................... 18 ISSN 0267-9272 Office: Burlington House, Piccadilly, London, W1V 9AG PRELIMINARY ECLIPSING BINARY LIGHT CURVES TONY MARKHAM Here are some light curves showing the recent behaviour of some Eclipsing Binaries. The light curves for RZ Cas, Beta -
QUALIFIER EXAM SOLUTIONS 1. Cosmology (Early Universe, CMB, Large-Scale Structure)
Draft version June 20, 2012 Preprint typeset using LATEX style emulateapj v. 5/2/11 QUALIFIER EXAM SOLUTIONS Chenchong Zhu (Dated: June 20, 2012) Contents 1. Cosmology (Early Universe, CMB, Large-Scale Structure) 7 1.1. A Very Brief Primer on Cosmology 7 1.1.1. The FLRW Universe 7 1.1.2. The Fluid and Acceleration Equations 7 1.1.3. Equations of State 8 1.1.4. History of Expansion 8 1.1.5. Distance and Size Measurements 8 1.2. Question 1 9 1.2.1. Couldn't photons have decoupled from baryons before recombination? 10 1.2.2. What is the last scattering surface? 11 1.3. Question 2 11 1.4. Question 3 12 1.4.1. How do baryon and photon density perturbations grow? 13 1.4.2. How does an individual density perturbation grow? 14 1.4.3. What is violent relaxation? 14 1.4.4. What are top-down and bottom-up growth? 15 1.4.5. How can the power spectrum be observed? 15 1.4.6. How can the power spectrum constrain cosmological parameters? 15 1.4.7. How can we determine the dark matter mass function from perturbation analysis? 15 1.5. Question 4 16 1.5.1. What is Olbers's Paradox? 16 1.5.2. Are there Big Bang-less cosmologies? 16 1.6. Question 5 16 1.7. Question 6 17 1.7.1. How can we possibly see galaxies that are moving away from us at superluminal speeds? 18 1.7.2. Why can't we explain the Hubble flow through the physical motion of galaxies through space? 19 1.7.3. -
Shorter Communications a Reconstruction of a Tahitian Star Compass Based on Tupaia's “Chart for the Society Islands With
SHORTER COMMUNICATIONS A RECONSTRUCTION OF A TAHITIAN STAR COMPASS BASED ON TUPAIA’S “CHART FOR THE SOCIETY ISLANDS WITH OTAHEITE IN THE CENTER” ANNE DI PIAZZA Centre National de Recherche Scientifique—Centre de Recherche et de Documentation sur l’Océanie, Marseille When Europeans first ventured into the Pacific they had to grapple with three almost inconceivable notions: (i) that Pacific Islanders could guide their canoes successfully over long distances without instruments, while they, the Europeans, had spent centuries developing the compass, the sextant and the chronometer for navigation; (ii) that the islanders could hold mental maps, while they, the Europeans, had spent centuries developing ways of representing a curved world on a flat map; and (iii) that Pacific islanders could memorise and transmit knowledge of numerous star paths, as well as “wind” or “island compasses” orally, in contrast to the almanacs and various mathematical tables created over centuries in Europe. This encounter of two schools of navigation, one technically sophisticated and based largely on written knowledge, the other an oral system, has lead to considerable “méconnaissance” (Turnbull 1998)—not the least concerns methods of way finding and mental cartography. It is perhaps no surprise that Tupaia, the high priest and navigator encountered by Cook in Tahiti in 1769, had some difficulty convincing the Captain of the accuracy of the “situation of the islands” he knew of since hidden behind the Chart he drew was a body of local knowledge encompassing indigenous geography, astronomy and navigation. All of these domains were confounded into one “art of navigation” by Europeans. In Oceania, the “… art of navigation includes a sizable body of knowledge developed to meet the needs of ocean voyaging… local navigators have had to commit to memory their knowledge of the stars, sailing directions, seamarks…” (Goodenough and Thomas 1987: 3). -