Frontier in Astronomy- Exam 1 study guide
Frontier in Astronomy- Exam 1 study guide PHY 21430
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This 6 page Study Guide was uploaded by Kathryn Notetaker on Friday October 14, 2016. The Study Guide belongs to PHY 21430 at Kent State University taught by Spyridon Margetis (P) in Fall 2016. Since its upload, it has received 23 views. For similar materials see FRONTIERS IN ASTRONOMY in Physics at Kent State University.
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Date Created: 10/14/16
Astronomy exam 1 study guide Gamma Rays a type of electromagnetic radiation cannot be focused can be detected but not imaged most energetic frequency on the spectrum short wavelengths blackbody radiation a type of electromagnetic radiation the specific spectrum and intensity depends on the temperature of the body Doppler effect and wavelengths if one is moving away from a source of radiation, the wavelength is longer (lower frequency) if moving towards the source, the wavelength is shorter (higher frequency) how Rilles are formed from volcanic activity that happened more than 3 billion years ago, not from impact lunar rotation moon rotates 27.32 earth days Mercury's magnetic field vs. Earth's field mercury has a weak magnetic field , while earth has a strong one Newtonian reflector telescope convex primary mirror flat secondary mirror eyepiece located on top and side of telescope Chandra x-ray observatory supplies high resolution x-ray images from space Astronomical telescope primary purpose is to collect a lot of light and bring it to a focus. 2 main categories: refractor or reflector prime focus reflector 1 optical surface concave mirror Full Moon rises at sunset, and sets at sunrise Earth’s days solar day- about 24 hours not a true day noon to noon how the sun appears to be in the same place at 2 consecutive times Sidereal day- when the earth makes a full revolution true day shorter than solar day by 4 mins every day, the earth moves about 1 degree around the sun earth has to cover this extra degree 360 degree in 24 hours 24*60 =1440 minutes to cover the extra degree it needs 1440/360=4 in a week, the sidereal time is about 28 mins shorter ex. If a star rises about 9 PM tonight, and with the sidereal day being four minutes less than the solar one, then in a month it will rise about 7 PM. Constellations Groups of stars making an apparent pattern in the celestial sphere 88 in the whole sky as the sun moves in the sky, it goes through 12 constellations today it goes through 13 The ozone layer in stratosphere below the mesosphere absorbs most of the sun’s UV radiation The continuing rise in the carbon dioxide in our atmosphere cause surface temperatures to rise. Plate motion plates collide , one can slide below the other or raise the other one highest mountains result from plates colliding the Himalayas. driven by convection Galileo’s observations: moon has mountains and valleys like earth sun has sunspots and rotates Jupiter has moons-smaller objects rotate around larger venus has phases proved that Ptolemy's epicycles could not be correct in keeping Venus between us and the Sun. comets a mixture of ices and dust will speed up as it approaches the Sun orbital eccentricity how much the orbit is off-centered The orbits of most of the planets have eccentricities close to zero. retrograde an apparent change in the direction of the motion of a planet a planet appears to move westward for weeks at a time Ptolemaic model had no explanation for retrograde motion preserved earth at center scientists no longer follow this model introduced eccentric motion, epicycles, deferent and equant to deal with various effects both the Ptolemaic model and Copernicus model agree that all orbits must be perfect circles Kepler's Laws of Planetary Motion the orbits of the planets are ellipses, not circles, with the sun at one focus the line joining the sun and the planet sweeps out equal areas in equal times square of period of planet’s orbital motion (P) is proportional to cube of semi major axis (a) ratio P^2/a^3 should be constant properties of planetary orbits perihelion: closest approach to the sun Aphelion: farthest distance from sun classic continuous spectrum contains many different colors or wavelengths a rainbow photoelectric effect when light shines on metal, electrons can be emitted frequency must be higher than minimum characteristic of material increased frequency- more energetic electrons increased intensity-more electrons, same energy can only be understood if light behaves like particles- a quantum effect in order to release electrons from a solid, the light must have a short wavelength spectroscopy the collection of observational and theoretical techniques that enables us to analyze the way in which atoms absorb and emit light By looking at the light they absorb and emit we can identify the atoms in the composition of stars, nebula, etc. Terrestrial planets small sized planets mercury, venus, earth, mars small and rocky close to the sun rotate slowly weak magnetic fields few moons no rings lie inside the asteroid belt Jovian planets larger planets Jupiter, Saturn, Uranus, Neptune gaseous surface far from sun rotate quickly strong magnetic fields many moons and rings lie beyond the asteroid belt sound waves and electromagnetic radiation transfer energy Of all the forms of electromagnetic radiation, the one with the lowest frequency is radio waves kelvin- The temperature scale that places zero at the point where all atomic and molecular motion ceases X-ray telescopes located in orbit around the Earth because xrays don’t reach the surface of the earth will not reflect off mirrors as other wavelengths do will reflect at a very shallow angle and can therefore be focused ex. supernova remnant Cassiopeia A 10,000 light years above earth white= brightest, red= faintest visible in optical part of the spectrum Kirchhoff’s laws- 3 spectroscopic rules luminous solid, liquid or dense gas produces continuous spectrum low density hot gas produces emission spectrum continuous spectrum incident on cool, thin gas produces absorption spectrum identical in color and energy to emission lines of the same gas if hot enough to glow using these laws, astronomers begun to first analyze the sun’s spectrum and identify the elements in it they found a mysterious element with unknown spectral lines called helium (Helios-sun) later found on earth as well line broadening-different causes thermal broadening: atoms move randomly produce broadened spectral lines as their individual redshifted and blue shifted emission lines merge in our detector the hotter the gas, the greater the degree of thermal broadening the Doppler shift (radial velocity)may cause thermal broadening of spectral lines rotation of spectral lines through the Doppler effect as a star rotates one side moves towards us while the other moves away the more rapid the rotation, the greater the broadening Earth’s atmosphere made up 80% of nitrogen and 20% of oxygen small amounts of noble gasses : carbon dioxide and vapor starts with troposphere (contains life) stratosphere: ozone layer mesosphere ionosphere exosphere most of the atmosphere except troposphere is at the freezing or below freezing temperatures troposphere contains weather and all phenomenon important to life forms Clouds form primarily at the boundary between troposphere and stratosphere tidal variation first quarter- least full/ new moon- most extreme convection- the process that physically transfers heat from a lower (hotter) to a higher (cooler) level craters of the moon about 10 times as wide as the meteoroid creating them and twice as deep rock is pulverized to a much greater depth than the size of meteorite ejected dust covers whole surface of moon most lunar craters date to at least 3.9 billion years ago; much less bombardment since then come in all sizes, from very large to very small Regolith- thick layer of dust left by meteorite impacts moon is still being bombarded especially by very small micrometeoroids Surface features on the moon moon has large dark flat areas due to lava flow called maria (early observers thought they were oceans) largest is called mare imbrium, sea of showers (1100 km diameter) it also has highlands called terrae has many craters (=bowl in Greek) from meteorite impacts maria have more iron, terrae more aluminum, hence color difference Surface features on mercury mercury cannot be imaged well from earth; best pictures are from messenger mercury surface similar to the moon many craters, no clouds rivers or dust storms cratering is similar to the moon, but less Mercury is intermediate between the moon and mars summer solstice-the Sun stops its northward motion along the ecliptic solar eclipse occur when earth, moon and sun is covered by the moon only occurs during a new moon Asteroids densest form of interplanetary debris rocky composition most orbit between orbits of mars and jupiter Cassegrain focus a small mirror is placed, diverts back and through the primary mirror to the back of the telescope, makes focal length much longer ex. hubble space telescope Telescope invented around 1600 galileo built his own telescopes built on mountain tops improve seeing by reducing the amount of air above the observer
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