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Introduction Dr Ken Rice Astronomy 1G Welcome Dr Avery Meiksin Dr Ken Rice Dr Mike Hawkins [email protected] (Course Organiser) [email protected] [email protected] Astronomy 1G Astronomy 1G : Galactic and Cosmological Science This is an introductory Astrophysics course in which you will apply basic physics technique to astrophysical situations. This course will focus on the large scale universe and will discuss, amongst other things, black holes, galaxies and cosmology. The Astronomy 1S course does not follow a single textbook closely. Some suitable books are ”Introductory Astronomy and Astrophysics” by M. Zeilik and S.A. Gregory. Some material may come from “The Cosmic Perspective” by Bennett, Donahue, Schneider and Voit. Astronomy 1G Online course material The course homepage can be accessed by registered students through the MyEd portal https://www.myed.ed.ac.uk/. The website will include course material and copies of the lecture notes. All notices, announcements, and assessment grades will also be posted on this website, and there will be a discussion board allowing students to ask questions about the course or provide feedback. The website also contains a link to the registration form that must be completed so that tutorial groups can be arranged. Astronomy 1G Tutorials Each student will attend a total of 5 tutorials, 1 every 2 weeks. Tutorials will be held on Mondays and Fridays from 15.00 to 15.50, and students will be divided into groups during the first week. You must fill out a registration form to be assigned to a tutorial group. During these tutorial sessions, you will work in groups to answer questions that will be similar to those that you will see in the exam. At the end of each two week period you will hand in your solutions and two of these solutions will be assessed. The best 4 tutorial marks out of 5 will count towards your final degree mark. You are encouraged to hand in all 5 sets of tutorial solutions, but by using the best 4 out of 5 means that students can miss one tutorial, if necessary, without being penalised. The tutorial deadlines will generally be the first lecture on the Monday after the final tutorial of each two week period. The exact dates of these lectures are shown in the timetables at the end of this booklet. We will not accept work that is handed in after these deadlines. Astronomy 1G Assessed Coursework In addition to the tutorials, you will be asked to do one piece of coursework that will be assessed. Details of the assignment (which may be essay, poster or numerical work) will be given several weeks in advance. You will have a choice of options for each assignment. You must complete the coursework and hand it in on time. It will be marked and returned to you; there is a marking penalty of 5% per working day, for five days, with a mark of zero thereafter, for late work. The assessed coursework is included in the final mark for the course. This means that any marks lost for late coursework make it harder to pass the course. You must include a “Own Work Declaration” when handing in the coursework. A mark will not be given if this form is not signed and returned with your work. The form is available from the course webpage on WebCT or can be downloaded from the School’s website. Astronomy 1G Observing Free tickets for the Visitor Centre’s public observing sessions on Friday nights will be able for first-year students interested in some stargazing and perhaps thinking about getting involved in outreach work. These tickets are limited and booking is essential. Contact the Visitor Centre (0131-6688404, 2-4pm, [email protected]). Astronomy 1G What is required to pass the course At the end of the course there will be a two-hour exam consisting of a multiple choice section, a short questions sections, and a problem-solving/long questions section. The course grade will depend on the degree exam, the coursework mark, and the tutorial marks. To the pass the course you will need an overall pass mark (40% on the University Common Marking scale) and you must score a minimum of 35% on the Degree Examination itself. The overall pass mark is calculated from: 2/3 examination 1/6 coursework assignment 1/6 assessed tutorial problems Astronomy 1G Astronomy 1G: Galactic and Cosmological Science 7 January to 21 March Monday 14.00 Appleton Tower, Theatre 1 Monday 16.10 Appleton Tower, Theatre 1 Friday 14.00 Appleton Tower, Theatre 1 Week 1 2 3 4 5 6 7 8 9 10 Date 7 Jan 11 Jan 14 Jan 18 Jan 21 Jan 25 Jan Day/Time M2, M4 F2 M2, M4 F2 M2, M4 F2 28 Jan M2*, M4 1 Feb 4 Feb 8 Feb 11 Feb F2 M2, M4 F2 M2*, M4 15 Feb 18 Feb 22 Feb 25 Feb F2 M2, M4 F2 M2*, M4 29 Feb 3 Mar 7 Mar 10 Mar F2 M2, M4 F2 M2*, M4 14 Mar 17 Mar 21 Mar 14-23 Apr F2 M2, M4 F2 Module Science of Astronomy Science of Astronomy Science of Astronomy Science of Astronomy The Milky Way and Galaxies The Milky Way and Galaxies Coursework assignment set: Monday 28 Jan. The Milky Way and Galaxies *28 Jan, M2: Tutorial 1 deadline. The Milky Way and Galaxies Active Galaxies and Black Holes Active Galaxies and Black Holes Active Galaxies and Black Holes *11 Feb, M2: Tutorial 2 deadline. Active Galaxies and Black Holes The Distribution of Galaxies The Distribution of Galaxies The Distribution of Galaxies *25 Feb, M2: Tutorial 3 deadline. Coursework deadline: Friday 29 Feb. The Distribution of Galaxies Cosmology Cosmology Cosmology *10 Mar, M2: Tutorial 4 deadline. Cosmology Short practice exam in M2, feedback in M4. 21 Mar, F2: Tutorial 5 deadline. Exams. Astronomy 1G Lecturer Dr WKM Rice Dr M Hawkins Dr A Meiksin Dr M Hawkins Course Modules • The Science of Astronomy • The Milky Way and other Galaxies • Active Galactic Nuclei • The Distribution of Galaxies • Cosmology EXAMS ! Astronomy 1G The Science of Astronomy Astronomy 1G Ancient Observations • Not much light pollution – Ancient civilisations were probably much more aware of the night sky than we are today. • Middle Eastern Astronomers had watched the night sky for thousands of years – Eclipses – The motion of the planets – Patterns in the night sky and how they changed during the year Astronomy 1G Ancient Astronomy • Nearly all ancient civilisations practised astronomy at some level – Time of day or night – Seasons • Lunar calenders – Origin of months – Lunar year 11 days shorter than a solar year. – Metonic cycle (discovered by Meton in 432 B.C.) • On a solar calender, the lunar phases repeat every 19 years Astronomy 1G Using the Moon • The orientation of the crescent moon varies with season. – We know today that this is caused by the relative position of the Sun and moon at different times of the year. • Central Africans would use this to predict rainfall. – They did not need to know why, they simply had observed for long enough to notice the pattern. Astronomy 1G Scientific Method • What is science? – science is the process by which we try to understand the world around us • Science is quantitative – definitive not vague – criteria for testing • This is, surprisingly, a recent activity – Many Ancients civilisations believed the world worked “through the actions of the Gods” – Ancient Greeks were the first people who tried to explain the motions of astronomical objects without resorting to the supernatural. • Theory – is the endpoint of science – provides an explanation – it must be consist with existing observations – and, be able to predict testable results • Experimentation – explore and discover – test theories Astronomy 1G Ancient Greek Astronomy • • Thales (624 – 546 B.C.) and Anaximander (610 – 546 B.C.) 2 of the earliest Greek Astronomers. Pythagoras (560 – 480 B.C.) – Earth is a sphere floating at the centre of the celestial sphere. – Spheres were perfect and therefore were the basic shape of the heavens. • Geocentric model – Plato – all heavenly bodies move in perfect circles at constant speeds. – Even in Plato’s day, Greek observers knew this was wrong. – Retrograde motion. – Why did Mercury and Venus remain so close to the Sun. Astronomy 1G Ptolemy (100 -170 B.C.) • • Based his models on that of Hipparchus (190-120 B.C.) Still placed the Earth at the centre – Introduced small circles (epicycles) upon a larger circle (deferent). – Moved the centre of the deferent away from the Earth. – Introduced equants – centre of epcicyle moved with constant speed relative to the equant. • Ptolemy’s work was remarkably accurate. Centre of deferent x Equant – Could predict planetary positions to within a few degrees. – Remained in use for 1500 years until Copernicus (1473-1543) suggested a Heliocentric model for the Universe. Astronomy 1G Geocentric model • Ptolemy (1st century AD) supported the geocentric (earth centred) model of the universe. • This could explain a number of observations - The nightly rotation of the stars - The simple motion of the planets - The lack of motion of the stars relative to each other - Phases of the moon - Eclipses • Could not explain - Why Venus and Mercury stayed so close to the Sun. Astronomy 1G Renaissance • Despite the advances of Greek science, it had some shortcomings – A theory was right if it produced the correct answer. – Very little or no experimentation • Arostotle assumed that heavy objects had to fall faster than light objects. • Galileo (1564 – 1642) revolutionised science – Developed mechanics and studied how objects moved – His approach is at heart of modern science. – Also invented the telescope and made observations that supported the Heliocentric model of the Universe. Astronomy 1G The Heliocentric model • • Although not supported in Galileo’s days, Galileo’s observations provided evidence for a Heliocentric rather than Geocentric model Invented the telescope in 1608 – Sunspots - Sun not perfect – Mountains and craters on the moon – not a perfect sphere – Moons of Jupiter – not everything orbits the Earth. Astronomy 1G The Heliocentric Model • Nicholas Copernicus (1473 – 1543) proposed a Heliocentric (Sun centred) model for the universe. - The centre of the universe is near the Sun. - The distance from the Earth to the sun is tiny compared with the distance to the stars. - The rotation of the Earth accounts for the apparent daily rotation of the stars. - The apparent annual cycle of movements of the sun is caused by the Earth revolving round it. - The apparent retrograde motion of the planets is caused by the motion of the Earth from which one observes. Astronomy 1G Retrograde motion • Copernicus correctly stated that the farther a planet lies from the Sun, the slower it moves around the Sun. • The Earth can therefore pass an outer planet during its orbit. • When this occurs, the outer planet will appear to reverse its motion for a short time - The retrograde loop. Astronomy 1G Newton (1642-1727) • One of greatest scientist ever – Studied light and built telescopes • His greatest contribution was the Principia Mathematica – Laws of Motion and the Theory of Gravity Astronomy 1G Astrophysics • Generally can’t do experiments in the traditional sense • Primarily relies on observations – Still requires a measurement • Probes to planets, moons and comets • Direct measurements of interplanetary space • Collect radiation from galactic and extra-galactic sources – Experimentation, but not controlled. – Requires an understanding of the underlying physics • Mechanics • Radiation and matter • Astrophysics is not a fundamental science – Application of physics to understand objects in the Universe. Astronomy 1G What Science do we need to know • Gravitational dynamics – Planetary orbits – Binary stars – Galaxy rotation • Doppler effect – Determine velocities and together with gravitational dynamics determines masses – Expansion of the Universe • Blackbody radiation – Temperatures • Spectra – Temperatures and composition – Type of star/galaxy – Can be then used to determine distances Astronomy 1G Some useful numbers Astronomical unit (pc) : 1 parsec (pc) : Speed of light (c) : 1.5 x 1011 m (Sun Earth distance) 3 x 1016 m 3 x 108 m distance light travels in a year (nearest star – apart from Sun) 1 light second : distance to the moon 8 light minutes : distance to the Sun 1 light hour : distance across solar system 25 thousand light years : distance across the galaxy 150 thousand light years : distance to the Magellanic galaxies 1 million light years : distance to M31 (nearest big galaxy) 1000 million light years : “size” of universe 1 light year : Astronomy 1G