Honors Astronomy Exam 1 (Chapters 1-5) – Flashcards
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field of view
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the region you can see in the image
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solar system
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consists of the sun, its family of planets, and some smaller bodies, such as moons and comets
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planets
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small, spherical, non-luminous bodies that orbit a star and shine by reflected light
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star
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a self-luminous ball of hot gas that generates its own energy
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astronomical unit (AU)
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the average distance from earth to the sun, which is equal to 1.5 x 10^8
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light-year (ly)
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distance light travels in one year
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galaxy
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a great cloud of stars, gas, and dust held together by the combined gravity of all of its matter
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Milky Way
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band of stars seen at night in the sky
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Milky Way Galaxy
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the name of our galaxy
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spiral arms
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places where stars are formed from clouds, gas, and dust
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universe
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billions of galaxies, each containing billions of stars and billions of planetary systems
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constellations
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groups of stars given names of celebrated heroes, gods, and mythical beasts
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asterisms
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less formally defined groupings of stars
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magnitude scale
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a system written by Ptolemy that measures the brightness of stars from 1 to 6; the brighter the star the lower the number and vice versa
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apparent visual magnitude (mv)
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how bright stars appear to the human eyes observing from earth
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flux
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the amount of light energy that hits one square meter in one second
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zenith
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spot directly overhead
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nadir
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spot directly below
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meridian
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north to your zenith to south
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horizon
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where the sky meets ground
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altitude
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angle above the horizon
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circumpolar constellations
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stars that never rise or set
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angular distance
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the angle between two lines extending from your eye to the two objects
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arc minutes
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1/60th of a degree
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arc seconds
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1/60th of an arc minute
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angular diameter
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the angular distance from one edge of the object to the other
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precession
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the weight of the top tends to make it tip over, and this combines with its rapid rotation to make its axis sweep out of the shape of a cone
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rotation
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the turning of a body on its axis (spin)
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revolution
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the motion of a body around a point outside the body (orbit)
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ecliptic
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the apparent path of the sun against the background of the stars
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evening star
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any planet visible in the evening sky
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morning star
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any planet visible in the sky shortly before sunrise
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vernal equinox
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the point where the sun crosses the celestial equator going northward
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summer solstice
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the sun at its most northern point
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autumnal equinox
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the point where the sun crosses the celestial equinox going southward
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winter solstice
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the sun at its most southern point
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zodiac
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a band around the sky extending 9 degrees above and below the ecliptic
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horoscope
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a diagram showing the location of the sun, moon, and planets around the ecliptic and their position above or below the horizon for a given date and time
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Milankovitch hypothesis
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small changes in Earth's orbit, precession, and inclination affect Earth's climate and can cause ice ages
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scientific argument
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a careful presentation of theory and evidence in a logical discussion
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lunar eclipse
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the moon moves through the shadow of the earth
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umbra
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the region of total shadow
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penumbra
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the region of partial shadow
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totality
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the period of total eclipse
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sidereel period
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the moon orbits eastward around the earth in 27.32 days
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synodic period
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a complete cycle of lunar phases takes 29.53 days
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solar eclipse
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the moon is just the right size to cover the bright disk of the sun
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photosphere
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the surface of the sun
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chromosphere
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the higher layers of the sun's atmosphere
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corona
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the sun's outer atmosphere
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prominences
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eruptions on the solar surface
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diamond-ring effect
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a tiny bit of the photosphere does not completely drown out the fainter corona, which forms a silvery ring of light, with the brilliant spot of photosphere gleaming
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perigee
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the moon's point of closest approach to earth
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apogee
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the most distant point in the moon's orbit
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annular eclipse
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a solar eclipse in which a ring of the photosphere is visible around the disk of the moon
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nodes
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the point where the moon passes through the plane of earth's orbit
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Saros cycle
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the pattern of eclipses repeats every 6585.3 days
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uniform circular motion
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Plato concluded that all motion in the sky must be made up of combinations of circles turning at uniform rates
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geocentric universes
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the argument that Earth was imperfect and lay at the center of the universe
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parallax
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the apparent motion of an object because of the motion of the observer
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epicycle
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a small circle that the Aristotle model said the earth followed
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deferent
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a large circle that the Aristotle model said the earth slid around
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equant
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the point in which Ptolemy supposed that the center of the epicycle moved in such that it appeared to move at a constant rate
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heliocentric universe
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the sun is the center of the universe
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ellipse
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a figure that can be drawn around two points, called the foci, in such a way that the distance from one focus to any point and back to the other focus equals a constant
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semimajor axis
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(a) half of the longer diameter in an ellipse
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eccentricity
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(e) half the distance between the foci divided by the semimajor axis in an ellipse
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mass
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a measure of the amount of matter in the object
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inverse square relation
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the force of gravity decreases as the square of the distance between the objects increases
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circular velocity
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the velocity needed to stay in a circular orbit
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geosynchronous satellite
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the orbit eastward with the rotation of earth and remains above a fixed spot
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center of mass
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the balance point of the system
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closed orbits
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return the orbiting object to its starting point
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escape velocity
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the velocity needed to leave a bodt
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open orbit
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does not return the orbiting object back to its starting point
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spring tides
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twice a month, at the new moon and the full moon, the moon and the sun produce tidal bulges that add together and produce extreme tidal changes; high tide is very high and low tide is very low
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neap tide
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less extreme tides at the first- and third-quarter moons when the sun and moon pull at right angles to each other; and the sun's tides cancel out some of the moon's tides
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electromagnetic radiation
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light made up of both electric and magnetic fields
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wavelength
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distance between peaks of the wave
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frequency
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the number of waves that pass a stationary point in one second
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photon
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a particle of electromagnetic radiation
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spectrum
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an array of electromagnetic radiation displayed in order of wavelength
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nanometer
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(nm) one billionth of a meter
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angstrom
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one-tenth of a nanometer
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infrared
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(IR) non-visible light that your body detects as heat
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atmospheric windows
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wavelength bands that that allow visible light, some shorter wavelength infrared radiation, and some radio waves to reach earth's surface
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refracting telescope
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telescope that uses a lens to gather and focus light
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reflecting telescope
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telescope that uses a mirror to gather and focus light
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primary lens
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the main lens in a refracting telescope
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primary mirror
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the main mirror in a reflecting telescope
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eyepiece
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a piece used to magnify the image and make it convenient to view
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chromatic aberration
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color separation
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achromatic lenses
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lenses with two components made of different kinds of glass, and thereby bring two different wavelengths to the same focus
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optical telescopes
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telescopes that collect visible light
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radio telescopes
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telescopes that collect radio waves
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light-gathering power
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the ability of a telescope to collect light
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resolving power
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the ability of the telescope to reveal fine detail
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diffraction fringe
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unavoidable blurring of light
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seeing
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the amount of image blurring due to atmospheric conditions
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magnifying power
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its ability to make images bigger
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light pollution
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the brightening of the night sky by light scattered from artificial outdoor lighting
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photographic plate
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first device used by astronomers to record images of celestial objects
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photometers
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sensitive light meters used to measure the brightness of individual objects very precisely
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charge-coupled devices
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(CCDs) a specialized computer chip containing millions of microscopic light detectors arranged in an array about the size of a postage stamp
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digitized
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converted to numerical data
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representational-color
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colors represent different aspects on the object such as intensity, rather than visible color
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spectrograph
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spreading out light according to wavelength
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spectral lines
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dark or bright lines that cross the spectrum at specific wavelengths
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adaptive optics
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high-speed computers monitor the distortion produced by turbulence in earth's atmosphere and rapidly alter some optical components to correct the telescope's image
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laser guide star
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the laser causes gas in earth's atmosphere to glow, producing an artificial star
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interferometry
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the method of synthesizing a "virtual" large telescope from two or more smaller telescopes
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cosmic rays
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subatomic particles traveling through space at tremendous velocities
