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Astronomy 1
exam 1
| Question | Answer |
|---|---|
| Ptolemy's Solar System Model | Center- Earth (the equant-earth moved of center) motion- circular planets orbit- Earth epicycles- yes (to explain retrograde motion) tables- Alfonsine (13th century update) problems- not truly geocentric |
| Copernicus' Solar System Model | Center- Sun motion- Circular planets orbits- Sun epicycles- Yes (Circular vs. ellipses) tables- prutenic problems-no parallax |
| Tycho's Solar System Model | center- Earth motion- circular planets orbit- sun (moon and sun orbit Earth) epicycles- no tables-none problems- never fully developed |
| Kepler's Solar System Model | center-Sun motion- Ellipses planets orbit- Sun epicycles- no tables- Rudolphine problems- None, the correct system |
| Coordinate Systems - Equatorial- Right Ascension | (longitude) Starting point- vernal Equinox values- 0h-24h how measured? E along C.E |
| Coordinate Systems - Equatorial - Declination | (latitude) starting point- celestial equator values- -90 - +90 how measured? angle above/below the C.E |
| Coordinate Systems - Observer-Based - Azimuth | Starting point- N point on Horizon values-0 degrees- 360 degrees how measured? E from N point around Horizon |
| Coordinate Systems- Observer-based - Altitude | Starting point-horizon values-0 degrees- 90 degrees How Measured? angle above horizon ***altitude of NCP is your latitude on Earth***** |
| distance= velocity x time | d=vt v= d/t |
| lightyears | the distance light will travel in a year 1 ly= (3x 10^8 m/s)(31,557,600s)= 9.46x10^15m = 6.32x 10^4 AU |
| hypothesis vs. theory | A hypothesis is more of a prediction, while theory is a well-known, well-tested principle |
| geocentric view | the Earth is at the center of the Universe |
| heliocentric view | sun centered universe |
| circumpolar | referring to the part of the sky,near either celestial pole, that can always be seen above the horizon from a specific location on Earth |
| circumpolar stars | given your latitude on earth, these stars NEVER set. Each day they complete a full circle around the pole |
| celestial sphere | originally thought to be the stars spinning around us. Now just a practical tool to help us map the sky. |
| latitude | the angular distance north (+) or south (-) from the equatorial plane of a nearly spherical body measured in degrees 0 - -/+90 "line used"-parallel line (parallel with equator) |
| longitude | measured in degrees 0 - 360 line used- meridian |
| horizon | where the sky meets the ground |
| Zenith | the point on the celestial sphere located directly overhead from an observer |
| meridian | the imaginary arc in the sky running from the horizon at due north through the zenith to the horizon at due south. It divides the observer's sky into eastern and western halves. |
| altitude | the location of an object above the horizon, measured by the angle formed between an imaginary line from an observer to the object and a second line from the observer to the point on the horizon directly below the object. (the angle above the horizon) |
| azimuth | angle measured E of N point along the horizon E point=90, S point=180, W point=270 |
| Ecliptic | the apparent path of the Sun in the sky, location of planets |
| precession | like a top, the Earth "wobbles" in its orbit |
| equinox | where the ecliptic and equator cross |
| solstice | points of Sun's greatest distance from celestial equator |
| Vernal Equinox coordinates | RA 0h, DEC 0 degrees |
| Summer solstice coordinates | RA 6h, DEC +23.5 degrees (tilt of sun's seasonal motion) |
| Autumnal Equinox Coordinates | RA 12h, DEC 0 degrees |
| Winter Solstice coordinates | RA 18h, DEC -23.5 degrees (tilt of sun's seasonal motion) |
| Sidereal period | (moon)time for one orbit - 27.3 days time for one rotation - 27.3 days Moon is tidally locked to Earth in synchronous rotation |
| synodic period | period for phase cycle - 29.5 days (moon) |
| phases of the moon | New moon - completely dark- on the sun side Waxing crescent, first quarter, waxing gibbous, full moon - completely whole- earth separates moon from sun waning gibbous, third quarter, waning crescent. |
| solar transit time | a day is defined by the time between two of the Sun's transits of the meridian = 24 hours. Due ONLY to Earth's rotation |
| lunar transit time | during 24 hours moon moves 13 degrees along orbit. SO *24 hours 52 minutes** moon rises 52 minutes later each day, because of both Earth's rotation and Moon's orbital motion |
| total solar eclipse | the Sun's corona (very thin gas,outer layers of Sun's atmosphere) is visible |
| aphelion | the point in a solar orbit that is farthest from the sun (distance varies by 3.4%) |
| perihelion | the point in a solar orbit that is closest to the sun (distance varies by 3.4%) |
| annular eclipses | a ring of the the very bright photosphere is visible during this eclipse. so the dim thin corona is not visible. (result of the varying distances of the sun and moon) |
| total lunar eclipse | entire moon enters Earth's shadow |
| Partial lunar eclipse | only part of the moon enters umbra |
| Penumbral eclipse | a barely noticeable dimming of moon as it passes through penumbra |
| zodiac | the constellation lying along the plane of the ecliptic (Aries, Taurus, Gemini, cancer, Leo, Virgo, Libra, Scorpius, Ophiuchus, Sagittarius, capricornus, Aquarius, Pisces) |
| role of node | the moon's orbit is tilted 5 degrees from the ecliptic, which is why there is not a eclipse every month. line rotates 19.4 degrees per year |
| Saros cycle | eclipse Prediction. sun- moon- nodes alignment repeats every 6585.3 days or 18 yrs, 11 and 1/3 day. *the 1/3 day means it takes 3 of these cycles for a solar eclipse to occur in the same area aka 54 years and 1 month |
| Retrograde Motion | planets passing one another "the apparent retrograde motion of the planets is caused by the motion of the Earth from which one observes" |
| Claudius Ptolemy | made the model with the insane amount of epicycles to explain retrograde motion |
| Nicolaus Copernicus | created book Little Commentary 1514, published after death, heliocentric |
| Tycho Brahe | part of Danish nobility, made very accurate observations, never fully realized system model because of death |
| Johannes Kepler | Tycho's assistant, abandoned circular motion |
| Kepler's first law of Planetary Motion | Orbits are ellipses (with the sun at a focus) |
| Kepler's second law of planetary motion | Equal area in equal time |
| Kepler's third law of planetary motion | P^2 = a^2 P=period of the orbit measured in years a= average distance from the sun measured in AU |
| Galileo's Discoveries | Moon imperfects (mountains and shadows), Sunspots(imperfections), Milky way is made up of stars, phases of Venus (completely incompatible with geocentric systems), Jupiter's moons |
| Newton's first law of motion | A body in motion stays in motion, unless acted upon by an outside force |
| Newton's second law of motion | F=ma Force= mass x acceleration |
| Newton's third law of motion | For every action, there is an equal and opposite reaction |
| inertia | the resistance of an object to a change in its motion |
| force | the unbalanced force applied to the object |
| mass | the object's resistance to change in motion |
| acceleration | the change in velocity due to the force over time |
| velocity | change in position over time |
| Universal Gravitation | every object in the universe attracts every other object with the force of gravity F= G [(m1 x m2)/ (r^2)] G- gravity constant 6.67x 10^-11 m1- mass of object 1 m2- mass of object 2 r- distance between objects |
| mass vs. weight | mass measures the amount of stuff where as weight measures the force, acceleration due to gravity |
| eccentricity | a measure of the departure of an ellipse from circularity |
| bound vs. unbound orbits | a closed orbit in which the velocity is less than the escape velocity vs. an orbit in which the velocity is greater than the escape velocity |
| escape velocity | the speed needed to escape gravitational effects |
| light as a wave and particle | its made up of massless particles called photons. photons always travel at the speed of light and they carry energy. the particle description tied to the wave description by relating the energy of a photon and the frequency or wavelength of the wave |
| Electromagnetic Spectrum | RADIO (10^4 long wavelength, low frequency & energy), MIRCOWAVE (1), INFRARED (10^-2), VISIBLE (10^-5), UV(10^-6), X-RAY(10^-8, GAMMA RAY (10^-12 short wavelength high f and energy) |
| interference | two waves can combine into a new wave, sometimes they add to make a larger wave, other times they cancel each other out |
| diffraction | light can bend around corners |
| reflection | light rays bounce off a surface, the angle of incidence is equal to the angle of reflection |
| refraction | light also transmits through the boundary, but the path changes direction |
| refractor telescope(Galileo) | uses lenses, primary convex lens, no secondary lens, problem- chromatic aberration |
| Reflector telescope (Newton) | uses mirrors,parabolic primary mirror, flat secondary mirror, problem- spherical aberration |
| Schmidt-Cassegrain (Catadioptric) | uses lenses and mirrors, primary spherical mirror with corrector plate, secondary parabolic mirror. no problems |
| Chromatic Aberration | a detrimental property of a lens in which rays of different wavelengths are brought to different focal distances from the lens |
| human eye | acts as a lens, pupil is the aperture, image that forms is actually inverted, your brain makes it upright VISIBLE SPECTRUM 350-700nm |
| integration time | how fast can we see new images? ~100 microseconds (.1 seconds) any faster and we can't separate them |
| quantum efficiency | how many photons needed to trigger a detection? 10 photons within 100 ms for 1 detection. 1/10 or 10% efficient |
| resolution | how can we separate two objects? must be separated by 1 arc minute, or 1' that is 1/30th the size of the moon |
| charged-coupled device (CCD) | photons release electrons from Si chip, made up of over 1,000,000 pixels. location & intensity of photon stored in electron trap, read out as current |
| spectrograph | a device that spreads out the light from an object into its component wavelengths |
| Diffraction limit | ratio of the slit width to the wavelength defines the amount of diffraction. Result is that images become blurred. |
| adaptive optics | electro-optical systems that largely compensate for image distortion caused by Earth's atmosphere. laser creates "Guide Star" whose light used to remove atmosphere's effect. |
| optical images | we can use the actual colors of the source TRUE COLOR IMAGES |
| radio & other bands of EM spectrum | we can't see them with our eyes, any color used is made-up |
| "true color" | assigning Red-Green_blue to low-medium-high energies |
| false color | assigning color to show a specific feature: brightness, intensity, velocity, etc. |
| interferometry | connecting multiple dishes increases effective area of the telescope and its resolution |
| hubble space telescope | discovered the nature of external galaxies, found evidence of big bang, launched april of 1990, VISIBLE and near IR, suffered spherical aberration-93 service mission. equipped with cameras & spectrometers |
| Compton Gamma Ray Observatory | launched April 1991, de-orbited June 2000, covered high energy photons from 30 keV - 30 GeV |
| Chandra x-ray observatory | launched from shuttle July 1999, large orbit out to 139,000, imaging & spectrometer .2 keV-12keV. orbits over 16,000km |
| Spitzer Space telescope | launched August 2003, orbits Sun, 85cm Diameter, 2 cameras& 1 spectrometer, sun shield,measures wavelength, entered "warm mode" in april 2009 when liquid He ran out |
| wavelength x frequency = speed of light | wavelength x f = 300 million meters/second (3x 10^8) f= complete cycles per second wavelength= distance between two crests or troughs |
| diffraction limit (angular resolution) | angular resolution = (206,265) (wavelength/aperture) D- aperture |
Created by:
emilyclawson
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