Elementary Astronomy: Final Exam (Ch 2-5, 7, 8, 16-20, 22, 23) – Flashcards
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constellations
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group of stars forming a recognizable, usually named after its apparent form or identified with a mythological figure; eighty-eight total with defined boundaries
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celestial sphere
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an imaginary sphere of which the observer is the center and on which all celestial objects are considered to lie
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Earth's rotation
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as the Earth rotates counter clockwise, the stars appear to rise in the East and set in the West
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diurnal motion
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the apparent daily motion of stars around the Earth, or more precisely around the two celestial poles
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Polaris (the North Star)
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the brightest star in the constellation Ursa Minor, and the 50th brightest star in the night sky; very close to the north celestial pole, making it the current northern pole star
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circumpolar
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situated around or inhabiting one of the Earth's poles
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sidereal day
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time is time measured with respect to the apparent motion of the 'fixed' stars in the sky due to the Earth's rotation
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solar day
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time measured with respect to the Sun's apparent motion in the sky; four minutes longer than the latter
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sidereal month
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the time the Moon takes to complete one full revolution around the Earth with respect to the background stars; 27.322 days
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synodic month
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also called lunar month; 29.531 days
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ecliptic
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a great circle on the celestial sphere representing the sun's apparent path during the year; lunar and solar eclipses can occur only when the moon crosses it
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the Zodiac
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the set of constellations on the ecliptic
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precession
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Earth's rotational axis undergoes a full cycle of this over the course of 26,000 years
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eclipse
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occur when the Sun, Earth, and Moon are positioned in a straight line
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lunar eclipse
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occurs when the Moon is in the Earth's shadow
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solar eclipse
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occurs when some portion of the Earth's surface is in the Moon's shadow
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Antikythera Mechanism
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an ancient analog computer designed to predict astronomical positions and eclipses for calendrical and astrological purposes, as well as the Olympiads, the cycles of the ancient Olympic Games
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heliocentric model
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a theory that places the Sun as the center of the universe, and the planets orbiting around it; replaced geocentrism, the belief that the Earth is the center of the universe
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retrograde motion
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apparent motion of a planet in a direction opposite to that of other bodies within its system, as observed from a particular vantage point
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arcminute
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a unit of angular measurement equal to one-sixtieth (160) of one degree
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stellar parallax
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the apparent shift of position of any nearby star (or other object) against the background of distant objects
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Kepler's First Law of Planetary Motion
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the orbit of a planet about the sun is an ellipse with the Sun at one focus
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Kepler's Second Law of Planetary Motion
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a line joining a planet and the Sun sweeps out equal areas in equal intervals of time
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Kepler's Third Law of Planetary Motion
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the square of a planet's orbital period is equal to the cube of its semi‐major axis; p^2 = a^3
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Newton's First Law of Motion
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objects in motion tend to stay in motion, and objects at rest tend to stay at rest unless acted upon by a force
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Newton's Second Law of Motion
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an object will accelerate if acted upon by a force according to the equation: force = mass times acceleration (f = m⋅a)
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Newton's Third Law of Motion
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for every action there is an equal but opposite reaction
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gravitational force
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the force that keeps you in your seat
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electromagnetic force
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the force that keeps you from falling through your seat
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strong nuclear force
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nuclear energy
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weak force
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radioactivity
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gravity
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the force that attracts a body toward the center of the earth, or toward any other physical body having mass
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mass
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a coherent, typically large body of matter with no definite shape
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weight
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a body's relative mass or the quantity of matter contained by it, giving rise to a downward force; the heaviness of a person or thing; equals mass times the acceleration on due to gravity
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tidal force
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a secondary effect of the force of gravity; arises because the gravitational force exerted by one body on another is not constant across it; the nearest side is attracted more strongly than the farthest side
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spring tides
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the high tides are very high and the low tides are very low; occur during the full moon and the new moon
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neap tides
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smaller difference between high and low tides; especially weak tides; occur during quarter moons
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speed of light
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a fundamental physical constant that is the speed at which electromagnetic radiation propagates in a vacuum; c = 3⋅10^8m/s
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electromagnetic waves
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waves that contain an electric field and a magnetic field and carry energy; they travel at the speed of light
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electromagnetic spectrum
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the range of wavelengths or frequencies over which electromagnetic radiation extends
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wave/particle dual nature of light
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every elementary particle exhibits the properties of particles and waves; addresses inability of concepts to fully describe the behavior of quantum-scale objects
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black body radiation
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idealized physical body that absorbs all incident electromagnetic radiation, regardless of frequency or angle of incidence; emits light at all wavelengths
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luminosity
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the intrinsic brightness of a celestial object (as distinct from its apparent brightness diminished by distance); the total is equal to the energy flux multiplied by the surface area of the object; L = E/t (energy, in joules, divided by time, in seconds)
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photons
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a particle representing a quantum of light or other electromagnetic radiation; carries energy proportional to the radiation frequency but has zero rest mass
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fluorescence
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visible or invisible radiation emitted by certain substances as a result of incident radiation of a shorter wavelength (such as X-rays or ultraviolet light)
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Doppler Shift
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the change in frequency of a wave (or other periodic event) for an observer moving relative to its source
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Wien's Displacement Law
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states that the black body radiation curve for different temperatures peaks at a wavelength inversely proportional to the temperature; λmax = 0.0029/T
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Stefan-Boltzmann equation
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states that the total energy radiated per unit surface area of a black body across all wavelengths per unit time; F = σT^4
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frequency
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measured in a unit call a hertz (abbreviated as Hz)
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energy flux
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the rate at which energy is emitted from one square meter of the surface of a black body; depends on temperature of object
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watt
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a watt is a joule of energy per second; 1W = 1j/s
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joule
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a joule is the energy required to lift a newton of weight to a height of one meter
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photoelectric effect
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observation that many metals emit electrons when light shines upon them
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Bohr Model of the Atom
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orbits are quantized; light is emitted only when an electron makes a transition from one orbit to a lower orbit
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terrestrial planets
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relatively close to the sun; Mercury, Venus, Earth, and Mars; Earth-like and more dense; primarily made of metal and rock
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jovian planets ("gas giants")
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relatively far from the sun; Jupiter, Saturn, Uranus, and Neptune; gaseous and much larger; made almost entirely of hydrogen and helium
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satellite
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an object that orbits a planet (like our Moon)
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spectroscopy
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the study of the interaction between matter and electromagnetic radiation
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Asteroid Belt
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a circumstellar disc in the Solar System located roughly between the orbits of the planets Mars and Jupiter; occupied by numerous irregularly shaped bodies called asteroids or minor planets
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Kuiper Belt
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a region of the solar system beyond the orbit of Neptune, believed to contain many comets, asteroids, and other small bodies made largely of ice
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asteroids
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made of rock; no liquid, ice, or atmosphere; large range in size
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Trans-Neptunian Objects
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composed of a mixture of rock and ice
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comets
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form when a pair of trans‐Neptunian objects collide and a fragment is sent into a highly elongated orbit the passes near the Sun
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meteoroids
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form when a pair of asteroids collide and send fragments into elongated orbits
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meteor
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a meteoroid that enters Earth's atmosphere and creates a "shooting star"
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meteorite
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the fragment that makes it to the surface of the Earth
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alpha decay
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radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and transforms into an atom with a mass number that is reduced by four and an atomic number that is reduced by two
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beta decay
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radioactive decay in which a proton is transformed into a neutron, or vice versa, inside an atomic nucleus
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Nebular Hypothesis
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the theory that the solar and stellar systems were developed from a primeval nebula; the Sun and the planets formed simultaneously form the same cloud of rotating gas; 4.5 billion years ago
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inverse square law
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any physical law stating that a specified physical quantity or intensity is inversely proportional to the square of the distance from the source of that physical quantity
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nuclear fusion
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reaction in which two or more atomic nuclei come very close and then collide at a very high speed and join to form a new nucleus; matter is not conserved because some of the matter of the fusing nuclei is converted to photons (energy)
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energy released in fusion
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E = mc^2; mass is energy
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neutrinos
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subatomic particles produced by the decay of radioactive elements; only particle the travels directly from the core to detectors on Earth
