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Astronomy, Astrophysics, and Cosmology
Astronomy, Astrophysics, and Cosmology Luis A. Anchordoqui Department of Physics and Astronomy Lehman College, City University of New York Lesson I February 2, 2016 arXiv:0706.1988 L. A. Anchordoqui (CUNY) Astronomy, Astrophysics, and Cosmology 2-2-2016 1 / 22 Table of Contents 1 Stars and Galaxies 2 Distance Measurements Stellar parallax Stellar luminosity L. A. Anchordoqui (CUNY) Astronomy, Astrophysics, and Cosmology 2-2-2016 2 / 22 Stars and Galaxies Night sky provides a strong impression of a changeless universe G Clouds drift across the Moon + on longer times Moon itself grows and shrinks G Moon and planets move against the background of stars G These are merely local phenomena caused by motions within our solar system G Far beyond planets + stars appear motionless L. A. Anchordoqui (CUNY) Astronomy, Astrophysics, and Cosmology 2-2-2016 3 / 22 Stars and Galaxies According to ancient cosmological belief + stars except for a few that appeared to move (the planets) where fixed on sphere beyond last planet The universe was self contained and we (here on Earth) were at its center L. A. Anchordoqui (CUNY) Astronomy, Astrophysics, and Cosmology 2-2-2016 4 / 22 Stars and Galaxies Our view of universe dramatically changed after Galileo’s telescopic observations: we no longer place ourselves at the center and we view the universe as vastly larger L. A. Anchordoqui (CUNY) Astronomy, Astrophysics, and Cosmology 2-2-2016 5 / 22 Stars and Galaxies Is the Earth flat? L. A. Anchordoqui (CUNY) Astronomy, Astrophysics, and Cosmology 2-2-2016 6 / 22 Stars and Galaxies Distances involved are so large that we specify them in terms of the time it takes the light to travel a given distance light second + 1 ls = 1 s 3 108 m/s = 3 108m = 300, 000 km × × light minute + 1 lm = 18 106 km × light year + 1 ly = 2.998 108 m/s 3.156 107 s/yr × · × = 9.46 1015 m 1013 km × ≈ How long would it take the space shuttle to go 1 ly? Shuttle orbits Earth @ 18,000 mph + it would need 37, 200 yr L. -
Introduction to Astronomy from Darkness to Blazing Glory
Introduction to Astronomy From Darkness to Blazing Glory Published by JAS Educational Publications Copyright Pending 2010 JAS Educational Publications All rights reserved. Including the right of reproduction in whole or in part in any form. Second Edition Author: Jeffrey Wright Scott Photographs and Diagrams: Credit NASA, Jet Propulsion Laboratory, USGS, NOAA, Aames Research Center JAS Educational Publications 2601 Oakdale Road, H2 P.O. Box 197 Modesto California 95355 1-888-586-6252 Website: http://.Introastro.com Printing by Minuteman Press, Berkley, California ISBN 978-0-9827200-0-4 1 Introduction to Astronomy From Darkness to Blazing Glory The moon Titan is in the forefront with the moon Tethys behind it. These are two of many of Saturn’s moons Credit: Cassini Imaging Team, ISS, JPL, ESA, NASA 2 Introduction to Astronomy Contents in Brief Chapter 1: Astronomy Basics: Pages 1 – 6 Workbook Pages 1 - 2 Chapter 2: Time: Pages 7 - 10 Workbook Pages 3 - 4 Chapter 3: Solar System Overview: Pages 11 - 14 Workbook Pages 5 - 8 Chapter 4: Our Sun: Pages 15 - 20 Workbook Pages 9 - 16 Chapter 5: The Terrestrial Planets: Page 21 - 39 Workbook Pages 17 - 36 Mercury: Pages 22 - 23 Venus: Pages 24 - 25 Earth: Pages 25 - 34 Mars: Pages 34 - 39 Chapter 6: Outer, Dwarf and Exoplanets Pages: 41-54 Workbook Pages 37 - 48 Jupiter: Pages 41 - 42 Saturn: Pages 42 - 44 Uranus: Pages 44 - 45 Neptune: Pages 45 - 46 Dwarf Planets, Plutoids and Exoplanets: Pages 47 -54 3 Chapter 7: The Moons: Pages: 55 - 66 Workbook Pages 49 - 56 Chapter 8: Rocks and Ice: -
• Classifying Stars: HR Diagram • Luminosity, Radius, and Temperature • “Vogt-Russell” Theorem • Main Sequence • Evolution on the HR Diagram
Stars • Classifying stars: HR diagram • Luminosity, radius, and temperature • “Vogt-Russell” theorem • Main sequence • Evolution on the HR diagram Classifying stars • We now have two properties of stars that we can measure: – Luminosity – Color/surface temperature • Using these two characteristics has proved extraordinarily effective in understanding the properties of stars – the Hertzsprung- Russell (HR) diagram If we plot lots of stars on the HR diagram, they fall into groups These groups indicate types of stars, or stages in the evolution of stars Luminosity classes • Class Ia,b : Supergiant • Class II: Bright giant • Class III: Giant • Class IV: Sub-giant • Class V: Dwarf The Sun is a G2 V star Luminosity versus radius and temperature A B R = R R = 2 RSun Sun T = T T = TSun Sun Which star is more luminous? Luminosity versus radius and temperature A B R = R R = 2 RSun Sun T = T T = TSun Sun • Each cm2 of each surface emits the same amount of radiation. • The larger stars emits more radiation because it has a larger surface. It emits 4 times as much radiation. Luminosity versus radius and temperature A1 B R = RSun R = RSun T = TSun T = 2TSun Which star is more luminous? The hotter star is more luminous. Luminosity varies as T4 (Stefan-Boltzmann Law) Luminosity Law 2 4 LA = RATA 2 4 LB RBTB 1 2 If star A is 2 times as hot as star B, and the same radius, then it will be 24 = 16 times as luminous. From a star's luminosity and temperature, we can calculate the radius. -
190 6Ap J 23. . 2 4 8C the LUMINOSITY of the BRIGHTEST
8C 4 2 . 23. J 6Ap 190 THE LUMINOSITY OF THE BRIGHTEST STARS By GEORGE C. COMSTOCK The prevailing opinion among astronomers admits the presence in the heavens of at least a few stars of extraordinary intrinsic bril- liancy. ‘ Gill, Kapteyn, and Newcomb have under differing forms announced the probable existence of stars having a luminosity exceeding that of the Sun by ten-thousand fold or more, possibly a hundred-thousand fold, and Canopus is cited as an example of such a star. It is the purpose of the present article to examine the evidence upon which this doctrine is based, and the extent to which that evidence is confirmed or refuted by other considerations. As respects Canopus, the case is presented by Gill, Researches on Stellar Parallax, substantially as follows. The measured par- allaxes of this star and of a Centauri are respectively ofoio and 0^762, and their stellar magnitudes are — 0.96 and+ 0.40; i. e., Canopus is 3.50 times brighter than a Centauri. The light of the one star, is therefore 3.50 times as great as that of the other. But since a Centauri has the same mass and the same spectrum as the Sun, and therefore presumably emits the same quantity of light, we may substitute the Sun in place of a Centauri in this com- parison, and find from the expression given above that Canopus is more than 20,000 times as bright as the Sun. I have sought for other cases of a similar character, using a method slightly different from that of Gill. -
A New Vla–Hipparcos Distance to Betelgeuse and Its Implications
The Astronomical Journal, 135:1430–1440, 2008 April doi:10.1088/0004-6256/135/4/1430 c 2008. The American Astronomical Society. All rights reserved. Printed in the U.S.A. A NEW VLA–HIPPARCOS DISTANCE TO BETELGEUSE AND ITS IMPLICATIONS Graham M. Harper1, Alexander Brown1, and Edward F. Guinan2 1 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309, USA; [email protected], [email protected] 2 Department of Astronomy and Astrophysics, Villanova University, PA 19085, USA; [email protected] Received 2007 November 2; accepted 2008 February 8; published 2008 March 10 ABSTRACT The distance to the M supergiant Betelgeuse is poorly known, with the Hipparcos parallax having a significant uncertainty. For detailed numerical studies of M supergiant atmospheres and winds, accurate distances are a pre- requisite to obtaining reliable estimates for many stellar parameters. New high spatial resolution, multiwavelength, NRAO3 Very Large Array (VLA) radio positions of Betelgeuse have been obtained and then combined with Hipparcos Catalogue Intermediate Astrometric Data to derive new astrometric solutions. These new solutions indicate a smaller parallax, and hence greater distance (197 ± 45 pc), than that given in the original Hipparcos Catalogue (131 ± 30 pc) and in the revised Hipparcos reduction. They also confirm smaller proper motions in both right ascension and declination, as found by previous radio observations. We examine the consequences of the revised astrometric solution on Betelgeuse’s interaction with its local environment, on its stellar properties, and its kinematics. We find that the most likely star-formation scenario for Betelgeuse is that it is a runaway star from the Ori OB1 association and was originally a member of a high-mass multiple system within Ori OB1a. -
The Metallicity-Luminosity Relationship of Dwarf Irregular Galaxies
A&A 399, 63–76 (2003) Astronomy DOI: 10.1051/0004-6361:20021748 & c ESO 2003 Astrophysics The metallicity-luminosity relationship of dwarf irregular galaxies II. A new approach A. M. Hidalgo-G´amez1,,F.J.S´anchez-Salcedo2, and K. Olofsson1 1 Astronomiska observatoriet, Box 515, 751 20 Uppsala, Sweden e-mail: [email protected], [email protected] 2 Instituto de Astronom´ıa-UNAM, Ciudad Universitaria, Apt. Postal 70 264, C.P. 04510, Mexico City, Mexico e-mail: [email protected] Received 21 June 2001 / Accepted 21 November 2002 Abstract. The nature of a possible correlation between metallicity and luminosity for dwarf irregular galaxies, including those with the highest luminosities, has been explored using simple chemical evolutionary models. Our models depend on a set of free parameters in order to include infall and outflows of gas and covering a broad variety of physical situations. Given a fixed set of parameters, a non-linear correlation between the oxygen abundance and the luminosity may be established. This would be the case if an effective self–regulating mechanism between the accretion of mass and the wind energized by the star formation could lead to the same parameters for all the dwarf irregular galaxies. In the case that these parameters were distributed in a random manner from galaxy to galaxy, a significant scatter in the metallicity–luminosity diagram is expected. Comparing with observations, we show that only variations of the stellar mass–to–light ratio are sufficient to explain the observed scattering and, therefore, the action of a mechanism of self–regulation cannot be ruled out. -
Measuring the Astronomical Unit from Your Backyard Two Astronomers, Using Amateur Equipment, Determined the Scale of the Solar System to Better Than 1%
Measuring the Astronomical Unit from Your Backyard Two astronomers, using amateur equipment, determined the scale of the solar system to better than 1%. So can you. By Robert J. Vanderbei and Ruslan Belikov HERE ON EARTH we measure distances in millimeters and throughout the cosmos are based in some way on distances inches, kilometers and miles. In the wider solar system, to nearby stars. Determining the astronomical unit was as a more natural standard unit is the tUlronomical unit: the central an issue for astronomy in the 18th and 19th centu· mean distance from Earth to the Sun. The astronomical ries as determining the Hubble constant - a measure of unit (a.u.) equals 149,597,870.691 kilometers plus or minus the universe's expansion rate - was in the 20th. just 30 meters, or 92,955.807.267 international miles plus or Astronomers of a century and more ago devised various minus 100 feet, measuring from the Sun's center to Earth's ingenious methods for determining the a. u. In this article center. We have learned the a. u. so extraordinarily well by we'll describe a way to do it from your backyard - or more tracking spacecraft via radio as they traverse the solar sys precisely, from any place with a fairly unobstructed view tem, and by bouncing radar Signals off solar.system bodies toward the east and west horizons - using only amateur from Earth. But we used to know it much more poorly. equipment. The method repeats a historic experiment per This was a serious problem for many brancht:s of as formed by Scottish astronomer David Gill in the late 19th tronomy; the uncertain length of the astronomical unit led century. -
Measuring the Speed of Light and the Moon Distance with an Occultation of Mars by the Moon: a Citizen Astronomy Campaign
Measuring the speed of light and the moon distance with an occultation of Mars by the Moon: a Citizen Astronomy Campaign Jorge I. Zuluaga1,2,3,a, Juan C. Figueroa2,3, Jonathan Moncada4, Alberto Quijano-Vodniza5, Mario Rojas5, Leonardo D. Ariza6, Santiago Vanegas7, Lorena Aristizábal2, Jorge L. Salas8, Luis F. Ocampo3,9, Jonathan Ospina10, Juliana Gómez3, Helena Cortés3,11 2 FACom - Instituto de Física - FCEN, Universidad de Antioquia, Medellín-Antioquia, Colombia 3 Sociedad Antioqueña de Astronomía, Medellín-Antioquia, Colombia 4 Agrupación Castor y Pollux, Arica, Chile 5 Observatorio Astronómico Universidad de Nariño, San Juan de Pasto-Nariño, Colombia 6 Asociación de Niños Indagadores del Cosmos, ANIC, Bogotá, Colombia 7 Organización www.alfazoom.info, Bogotá, Colombia 8 Asociación Carabobeña de Astronomía, San Diego-Carabobo, Venezuela 9 Observatorio Astronómico, Instituto Tecnológico Metropolitano, Medellín, Colombia 10 Sociedad Julio Garavito Armero para el Estudio de la Astronomía, Medellín, Colombia 11 Planetario de Medellín, Parque Explora, Medellín, Colombia ABSTRACT In July 5th 2014 an occultation of Mars by the Moon was visible in South America. Citizen scientists and professional astronomers in Colombia, Venezuela and Chile performed a set of simple observations of the phenomenon aimed to measure the speed of light and lunar distance. This initiative is part of the so called “Aristarchus Campaign”, a citizen astronomy project aimed to reproduce observations and measurements made by astronomers of the past. Participants in the campaign used simple astronomical instruments (binoculars or small telescopes) and other electronic gadgets (cell-phones and digital cameras) to measure occultation times and to take high resolution videos and pictures. In this paper we describe the results of the Aristarchus Campaign. -