Exam# 1 Review Exam is Wednesday October 11 h at 10:40AM, room FLG 280 Bring Gator 1 ID card Bring pencil #2 (HB) with eraser. We provide the scantrons No use of calculator or any electronic device during the exam Equations will be projected on the screen You can use the exam pages as scrap paper if you need to do calculations Keep the first page of the exam. Scores will be published using the exam number The exam has 30 questions, 5 possible answers, only one valid answer. Duration: 50 minutes Exam will include material from Ch 0, Ch1, Ch 2, Ch 3 and Ch 5 Power Point presentation. Chapter 0 Charting the Heavens Looking back in distance, looking back in time Definition of AU and light-year The celestial sphere The celestial equator, celestial poles, the ecliptic. Solstices and equinoxes The celestial coordinates: Right Ascension and Declination Reference (or origin) of Declination. Reference for Right Ascension Values of declination for North and South celestial hemispheres Constellations Reference object or points to define Solar and Sidereal days and the duration of these two days Understand the reason for the seasons. The 23.5 degrees tilt of the Earth s rotational axis The lunar phases and the relative positions of Sun, Moon and Earth for different phases Solar and lunar eclipses (relative positions of Earth-Moon-Sun and phases of the Moon) Tilt of the Moon orbital plane respect to the Earth orbital plane What is precession What is parallax
Chapter 0 Charting the Heavens Questions If a star has a Declination of +40 degrees, in which celestial hemisphere is it located and how far the celestial equator? What are the names of the two points in the celestial sphere where the Sun crosses the celestial equator? Declination of the Sun for Summer solstice? For Winter solstice? What is the relative location of the Moon, Sun and Earth for the different phases of the Moon? Where is the Sun respect to the Moon when it is full Moon. Where is the Sun when it is new Moon? Where is the Moon respect to the Sun s position for a lunar eclipse? For a solar eclipse? Why we don t see a solar or lunar eclipse every month? The 5 degrees difference is the orientation of the Earth orbital plane and the Moon orbital plane Why there are annular solar eclipses? What causes the seasons? Is it the changing distance of the Earth to the Sun? Do we have winter or summer in the north and southern hemisphere at the same time? Is it the tilt of the Earth rotational axis? What is the value of the tilt angle of the rotational axis of the Earth respect to the perpendicular to the orbital plane? What is the Earth s precession? What causes the Earth s precession? What is the effect of the precession in the position of the star Polaris? What is the duration of the precession cycle? What is parallax and stellar parallax? How can we use stellar parallax to calculate distance to a nearby star?
Chapter 1 The Copernican revolution Topics The contributions of Ptolemy, Copernicus, Brahe, Kepler and Galileo to astronomy The three Kepler s law of planetary motion The ellipse. Eccentricity of an ellipse: distance between the foci divided by the length of the semi major axis Newton s three laws of motion and his Universal Law of Gravitation Galileo observations with his telescope Deferent and epicycles in the geocentric model Questions: How was retrograde motion explained in the geocentric model? How do we explain the retrograde motion of Mars under the heliocentric model? What was Tyco Brahe contribution to astronomy? Which are the 3 Kepler s laws of planetary motion? 1st Law: Planets orbit the Sun in elliptical orbits 2 nd Law: The line connecting a planet with the Sun sweep equal areas in equal times 3 rd Law: p² = a³. Modified 3 rd law by Newton: p² = a³/m Which are the 3 Newton s law a motion? F= m a Newton law a gravity. How the gravitational force between two masses changes if we change one of the masses? How does it change if we change the distance? F = G (m₁ m₂)/ r² Four important discoveries Galileo did with his telescope and how some of them supported the heliocentric model Concept of mass and weight. How your mass change if you are on the Moon? How is your weight change is you are on the Moon? How do we determine the value in km of the AU?
Chapter 2 Light and matter Topics and concepts Parameters that describe a wave :Wavelength, amplitude, wave period, frequency Velocity of light: c The black body. The shape of the blackbody radiation curve The kinetic energy of the molecules or atoms: Proportional to the velocity squared (Ek = 1/2mv²). Temperature is a measure of the velocity (energy) of the particles (atoms and molecules in a gas). High temperatures means higher velocities and higher energies of the gas molecules Relation between color and temperature in a black body. The color of stars and their temperatures Thermal radiation, the radiation laws Wien s law (λmax = 0.29/T) Stefan s law (F = T 4 ) The three types of spectrum: continuous, line emission, line absorption Kirchhoff s laws of radiation Energy levels in an atom (Bohr s model) Electrons jumping between energy levels and the wavelength of the radiation emitted or absorbed The energy of a photon (E ph = h f = h c/ ) Velocity of a photon in vacuum: c The Doppler effect: Only if there is radial velocity. No Doppler effect if the velocity is perpendicular to the line of sight. Doppler effect: If the body is receding, red shift; if the body is approaching, blue shift
Chapter 2 Light and matter Questions Considering the color of a star, can you tell which star are cooler and which are hotter and why? If we increase the temperature of a body by 3 times, how is the total radiative flux change? Use F = T4 If we increase the temperature of an object what happens to the wavelength of the maximum or the peak of emission? Use λmax = 0.29/T What does the temperature means regarding thermal energy in a gas? Average kinetic energy of a gas proportional to molecular mass and the square of the speed What does the temperature measure? Is the velocity of propagation of a electromagnetic wave (light) wavelength dependent? What is the velocity of propagation of a radio wave? Velocity of propagations of a Gamma ray? Which of the two propagate (travel) faster? Energy of a radio photon (or radio wave) Energy of a Gamma photon (or Gamma wave) Use: Eph = h f = h c/ Which of the two photons has more energy? What is Doppler red-shift. What does it tell you about the velocity and the direction is moving? If a star is coming towards the observer how are the spectral lines shifted? If the star is moving perpendicular to the observer how are the spectral lines shifted? What can we learn from spectral analysis? Composition, temperature, line-of-sight velocity, rotations rate, pressure of a gas and the presence of magnetic field (Zeeman effect).
Chapter 3 Telescopes Two types of telescopes: Reflectors (mirrors) and refractors (lenses) The two important parameter (or characteristics) of a telescope: Light Gathering Power (or light collecting area ) (LGP D² ) Resolution (Angular resolution λ/d ). Both characteristics depends on the diameter of the telescope Light gathering power depends on the square of diameter (collecting area) The resolution (angular resolution) of a telescope increases with the diameter The resolution is measured in arc second. A small number means better resolution The image of a star produced by a telescope has a central bright spot called the Airy disk The diameter of the Airy disk increase with decreasing diameter (aperture ) of a telescope Small diameter of a telescope, produce a larger Airy disk, bad resolution. Large diameter, smaller Airy disk, good angular resolution, better resolution Instrumentation attached to telescopes: CCD, spectrographs The effect of the terrestrial atmosphere in the formation of an image
Chapter 3 Telescopes Questions Why astronomers build bigger telescopes? Any advantage of having bigger telescopes? What is the objective of a reflecting telescope? Of a refracting telescope? What is the focal length of a telescope? What is the dependence of the diameter of a telescope with the light gathering power? What is the dependence of the diameter with the angular resolution of a telescope? If the separation between two star in a binary system is much smaller that the resolution of the telescope, will you be able to see those two star separated? Why? Can you see the craters on the moon with the naked eye? Why? The formula to compute the magnification of a telescope? Using high magnification, does it improve the resolution of a telescope? What happens to a pixel in a CCD when it is hit by photons? How a CCD stores an image in a computer? Images taking by IR, UV, X-rays or Gamma-ray telescopes can be represented by colors. Are those colors the colors that we can see with our eyes? What do the colors mean? What happen to the image of a star taking by a ground-based telescope when several short exposure are taking? Do stars twinkle? Do planets twinkle? Why? What can we learn about an object using spectroscopy?
Chapter 5 The Earth and Moon Topics The tides. The reason for the tides: The differential gravitational attraction of the Moon and the Sun on the oceans Important: Equations of escape velocity and average molecular speed How do we use these two formulas to predict if a celestial body (planets, satellites) will retain or lose an atmosphere? What are the parameters in each of the two equations? What are the two parameters involved in the escape velocity equation? The mass and radius of the body In the molecular speed equation, what are the two parameters? Temperature and molecular mass of gas The kinetic energy of a body and a molecule: proportional to mass and velocity squared Describe the greenhouse effect Gases that produce the greenhouse effect in the terrestrial atmosphere The ozone layer and the ozone hole. The internal structure of the Earth and Moon: Core, mantle, crust. Radioactive decay and the melting of the interior of the Earth and other terrestrial planets Heat generated by impact of small bodies with the Earth and other planets Differentiation The P and S seismic waves as tool to learn about the internal structure of the Earth Plate tectonics. The Earth magnetic field. Solar wind energetic particles trapped in the Earth magnetic field The terrestrial aurora Theory of formation of the Moon
Chapter 5 The Earth and Moon Questions What is the configuration of the positions of the Sun and Moon for the spring tides? For neap tides? How many high tides are in 24 hours period? Why? Why the tidal effect of the Sun is smaller than the tidal effect of the Moon? How do we know about the Earth interior? How are the P and S wave used? Equations for the escape velocity and the molecular velocity What is minimum ratio of escape velocity to mean molecular velocity so gases are retained in the atmosphere of a planet? Which gases may leave an atmosphere faster? Why? What causes the depletion of ozone in the atmosphere? What is the ozone hole and where it is located How can we explain the large density of the core of the Earth and the terrestrial planets? What is differentiation? What were the sources of heat that made the Earth to rise its internal temperature and melt? Name the three main greenhouse gasses present in the atmosphere of the Earth Name the two main gases in the atmosphere of the Earth Why the Moon has been able to preserve the impact crater? Why the Moon does not have an atmosphere? What are the lunar maria (mare) and what caused them? How do we explain the presence of Earth s magnetic field What are the two conditions that may explain the formation of magnetic field in a planet? Does the Earth meet these two conditions? What causes the terrestrial aurora? Describe the process that produces an aurora How the Earth s magnetic field and the ozone layer protect life on Earth? What are the theories of formation of the Moon? Which is the most accepted one?