Astronomy final study guide PDF

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This is a study guide for the astronomy final exam. Very detailed and it includes everything you need to know ...

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Seven brightest objects in the sky o Sun o Moon o Mars o Mercury o Jupiter o Venus o Saturn Androcentric: man is the center of the universe Geocentric: Earth is the center of the universe Age of universe: 14 billion years Age of sun: 5 billion years Age of earth: 4.5 billion years # of years humans have been around: 100,000 years There are 100 billion stars in the Milky Way The term galaxy comes from the Greek word “galaxias” meaning milky circle The name of our cluster of galaxies is called a supercluster, which contains 70 galaxies In 1929, Edwin Hubble proposed the idea that the universe was expanding o Said that all galaxies outside the local group are moving away from us, and the farther away they are, the faster they’re going Einstein’s E=mc^2 concerns energy and mass; energy has been transformed into mass AU is an astronomical unit, distance between earth and sun o 1 AU = 1.5 x 10^11 = 150 million km o Jupiter lies about 5.2 AUs from the sun o Mars is about 1.5 AU from the sun o 0.01 AU between Earth and moon Humans → Earth → solar system → Milky Way → local group → local supercluster Gravity keeps stars, planets, and galaxies in motion Dark energy keeps the universe expanding o Dominant form of energy in the universe Hydrogen and helium are the two lightest elements in the universe, which represent 98% of the solar system o Sun is made up of these elements o Formed from the Big Bang Carbon, oxygen, gold, and other heavy metals come from an explosion of stars known as a supernova Light is electromagnetic radiation o Radio waves o Infrared o X-ray o Ultraviolet Light year: distance light travels in one year o Speed of light is C = 3.0 x 10^8 m/s o 10 trillion km o Diameter of the Milky Way is about 100,000 light years Sirius, which is 8 light years away, is the brightest star in the sky

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Andromeda is the closest galaxy, which is 2.5 million light years away Speed of a planet’s rotation = 1000 km/hr Speed of a planet’s revolution = 100,000 km/ht Speed of sun = 70,000 km/hr Speed of galaxy = 300,000 km/hr Dark matter affects the motion of objects moving in that region; not many stars; located in the halo of the galaxy There is no center of the universe because everything is equally spread out The raisins in a cake model explains the expansion of the universe o Place raisins 1 cm apart from each other o The raisins spread during baking o Farthest things move fastest The farthest galaxy that modern telescopes are capable of seeing are up to 10 billion light years away Expansion of the universe suggests that Dark Energy is present The stars visible just after sunset are different from those visible just before sunrise because Earth rotates once a day No one on Earth can see the constellation Orion in June because Earth revolves around the Sun once each year The stars of Orion’s belt rise in the east and set in the west because Earth rotates once a day The solar system is located halfway between the center and edge of the visible disk of the galaxy Galaxy: a collection of a few hundred million to a trillion or more stars, bound together by gravity Stars made most of the oxygen nuclei in the solar system Big Bang: the event that marked the beginning of the expansion of the universe When we say the universe is expanding, we mean that the average distance between galaxies is increasing with time Nuclear fusion: the process of combining lighter weight nuclei to make heavier nuclei Sun and Earth formed in September The moon orbits the Sun once a year The patterns of the stars in our sky look the same every year because the stars in the constellations are so far away It takes one year for Earth to complete one orbit around the sun It takes 230 million years for the solar system to complete one orbit The distribution of the mass of the Milky Way is determined by studying the rotation of the galaxy The solar system travels 170,000 light years in one orbit Solar system is moving toward the star Vega at 70,000 km/hr Constellations are a group of stars that form a pattern o Constellations change because stars move o A region in the sky as seen from Earth 360 degrees in a circle 60 arcminutes in a degree 60 arcseconds in an arcminute

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3,600 arcseconds in a degree Polaris, the North Star, can be found above the North Pole o Will no longer be the North Star in 1,000 years because of Earth’s precession Earth’s axis causes the seasons o If Earth had no inclination, seasons would be very extreme and the sun would always be on the horizon at the poles Precession - rotation of axis; 26,000 years per cycle Everything rises in the east because of the Earth’s counterclockwise rotation o The moon rises in the east and sets in the west because Earth rotates once a day Full moon o Rises at 6pm o Max at midnight o Sets at 6am Waxing gibbous o Rises at 3pm o Max at 9pm o Sets at 3am 1st quarter o Rises at noon o Max a 6pm o Sets at midnight Waxing crescent o Rises at 9am o Max at 3pm o Sets at 9pm New moon o Rises at 6am o Max at noon o Sets at 6pm Waning crescent o Rises at 3am o Max at 9am o Sets at 3pm 3rd quarter o Rises at midnight o Max at 6am o Sets at noon Waning gibbous o Rises at 9pm o Max at 3am o Sets at 9am All moons except full and new can be seen during the day Requirements for solar eclipse include new moon and node, for lunar eclipse include full moon and node o Sun, Earth, Moon must be nearly perfectly aligned Three types of solar eclipses are total, partial, annular

In order for there to be a total eclipse, the Moon’s umbra must touch the area where you are located Saros cycle is the predicting of a solar eclipse o Each cycle lasts for 18 years and 11 ⅓ days o The next solar eclipse in the US is April 8th 2024 Retrograde motion is the apparent reversed motion of an object o Mars has caused the most controversy  When this happens to Mars, Earth is catching up with and passing by Mars in their respective orbits o Happens when Earth passes another planet, then the planet appears to move backward with respect to the background stars. But this is apparent as the planet’s true motion has not changed o Sun never goes through this Parallax refers to the fact that objects appear to be in different positions from different perspectives o A parallax angle of 1 second represents a distance of 3.26 light years o The closer the star is to us, the more parallax it exhibits o The farther a star is to us, the less parallax it exhibits Stellar parallax is the slight back-and-forth shifting of star positions that occurs as we view the stars from different positions in Earth’s orbit of the sun Certain constellations are visible in the evening only at certain times of the year because our evening view of space depends on where Earth is located in its orbit around the sun 2,000 stars are visible to the naked eye on a dark, clear night The point directly over the head is called the zenith If we have a new moon today, the next full moon will be in two weeks The Greeks rejected the idea that the Earth orbits the Sun because they could not measure a change in stars’ positions on the sky Celestial sphere o Earth is placed at the center of this o When we look in the sky, the stars all appear to be located on this o Does not physically exist o

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Process of science has 4 parts: o Observation o Interpretation o Measurement o Formulation Julius Caesar suggested the idea of having a leap year every four years Gregorian calendar o Named after Pope Gregory XIII who suggested that 5 days needed to be removed from the calendar, so October 5-10 were taken off Three aspects of ancient Greek science o Mathematics o Understanding the supernatural without gods and goddesses o Observation and reasoning

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Ptolemy explained the retrograde motion of planets by explaining that Mars moves in 2 circles, one around itself and one around the sun Ptolemy had the planets orbiting the Earth in perfect circles in his model of the universe to explain that planets sometimes appear to move westward, rather than eastward, relative to the stars in our sky The Big Three of the 16th century revolution in astronomy o Copernicus  Born in Poland  Learned the tables of planetary motion based on Ptolemaic model were inaccurate, so he wanted to find a better way  Sun-centered model for retrograde motion to determine the layout of the solar system  Copernican model didn’t work because it still used perfect circles o Tycho Brahe  Compiled the most accurate 1 arcminute with naked eye measurements  Still could not detect stellar parallax, still thought Earth was center of solar system  Hired Kepler  Recorded a nova, a bright star that appeared one evening and lasted for 18 months  May have solicited funds from wealthy donors to support science o Kepler  First tried to match Tycho’s observations with circular orbits  Kepler’s predicted positions differed from Tycho’s observations by only about 8 arcminutes, which led him to abandon the idea of circular orbits  Discovered the orbits are ellipses, which have foci, major/long axis, semimajor axis, minor/short axis, and eccentricity  Could not predict Mars’s orbit, which led him to consider an ellipse for orbit Galileo o Earth could not be moving because objects in air would be left behind o Noncircular orbits are not as perfect as heavens should be o If Earth were really orbiting the sun, we’d detect stellar parallax o Challenged the idea that objects in the heavens were perfect by observing sunspots on the Sun and mountains on the moon Kepler’s three laws o Planets move in an ellipse with sun at 1 focal point o Planets sweep out equal areas in equal time o P^2 = a^3; more distant planets orbit the sun at slower speeds  P = period, time of the cycle or year  A = average distance between sun and planet; AU units  Venus orbits the Sun at a slower average speed than Mercury  If a planet were discovered with an average distance from the sun of 100 AU, its period would be 1000 years  A planet that is twice as from from the Sun as Earth should have a period of more than 2 Earth years

An asteroid with an orbital period of 8 years lies at an average distance from the Sun equal to 4 AU # of stars known with time o Ancient times: 1,000 o 1600: 2,000 o 1712: 3,000 o 1918: 250,000 o Now: 16 million During the European Dark Ages, the scientific work of the ancient Greeks was preserved and further developed by scholars in Baghdad, Iraq The Muslim fast of Ramadan occurs during the ninth month of the lunar calendar, between new moons The Mediterranean and the Middle East is the part of the world that led to modern science which emerged from ancient civilizations The ancient goal of astrology was to predict future events affecting nature and people The ancient Greeks were the first people known to try to explain nature with models based on reason and mathematics, without resort to the supernatural Earth is moving fastest in its orbit during the winter because it is closest to the sun Perihelion: planet is closest to the sun, moving fastest Aphelion: plane is farthest from the sun, moving slowest Jupiter has the Galilean moons If Venus is in its full phase, then Earth would also be in its full phase Within the past 500 years, humans first learned that the Earth is not the center of the universe Four fundamental forces o Gravity o Electromagnetic o Strong nuclear o Weak nuclear Vector: magnitude, direction o Example: o Velocity Scalar: magnitude, temperature o Example: o Speed Velocity: change (displacement) over time Difference between speed and velocity Acceleration = change in velocity / change in time Change in acceleration / change in time is called jerk Centripetal acceleration is acceleration directly toward the center when spinning in a circle o Orbital motion results from this Force = mass x acceleration Newton’s universal gravitation equation is Fg = Gm1m2 / R2 Mass is the same anywhere in the universe, but weight changes depending where the body is. For example weight is different on the moon than on earth or at higher altitudes 

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Gravity for humans on earth is 9.8 m/s^2 and goes downward Speed tells us how far something will go in a certain amount of time Velocity tells us both speed and direction Momentum = mass x velocity The acceleration of gravity causes falling objects to fall faster by 9.8 m/s or 10 m/s with each passing second Newton’s laws o First - In the absence of a net force, an object will move with constant velocity; objects at rest tend to remain at rest o Second – what happens to an object when a net force is present; f=ma; a net force will change an object’s momentum o Third – every force is always paired with an equal and opposite reaction force

Two types of planets – terrestrial and jovian Albedo = % of light reflected 3 greenhouse gases are CO2, CH4, H2O planetesimal – accumulation of mass, few km in diameter, dust, rocks, pebbles protoplanets – keep getting bigger, takes a billion years, bigger than planetesimal convection – hot interior comes to surface and cools down metal and fast rotation help determine if a planet will have a strong magnetic field  which protects us from charged particles from the sun jovian planets are large planets, are orbited by many moons and rings, and have fast rotation Uranus and Neptune are blue because of the presence of Methane Jupiter and Saturn are made mostly of hydrogen and helium, while Uranus and Neptune are made mostly of hydrogen compounds/rock as well as hydrogen and helium

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Over 160 moons orbit the Jovian planets Small moons have no geological activity, medium have it in the past, large have it ongoing Sun o Radius = 108x radius of Earth and mass = 333,000x mass of Earth o Composition = Hydrogen and helium o Sun spots = cooler regions o Solar flares = releases of gas from sun o Solar wind = particles from sun o Pressure and temperature highest at the core at 10^ K o Each second, 600 tons of hydrogen  transformed by fusion into 596 tons of helium  leaves 4 million tons of mass converted into energy Mercury o Made of metal and rock; large iron core, desolate, cratered o Not much atmosphere o Very hot during the day (425 degrees C) and very cold at night (-170 degrees C) o 0.39 Au from the sun o radius is 0.38 radius of the earth, mass is 0.055 mass of earth o inclination at 0.0 degrees, albedo at 0.06, eccentricity is 0.206 o year 88 days, day 58.6 days Venus o 470 degrees C day and night o nearly identical in size to Earth o surface hidden by sulfuric clouds o hellish conditions due to an extreme greenhouse gas effect; presence of volcanoes o 0.72 Au from the sun o radius is 0.95 radius of earth, mass is .082 mass of earth o inclination at 177.3 degrees; no seasons o sun rises west o year is 224.67 days, day is 116.8 days o eccentricity is 0.007 Earth o Only surface of liquid water in solar system o Surprisingly large moon o Pangaea – all continents were together at some point o Core – highest density, center, iron and nickel o Mantle – medium density, rocky material o Crust- lower density, rock, surface o Lithosphere – coolest edge of the mantle o Impact cratering – meteor crater from asteroids, erosion destroys original crater o Volcanism – when molten rock (magma) finds a path thru lithosphere to the surface; called lava after it reaches the surface o Tectonics – structure of the crust; breaking of plates  earthquakes o Erosion – weather that destroys the surface like ice, wind, water

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o 77% nitrogen, 21% oxygen, 2% other The Moon o Some volcanic activity 3 billion years ago must have flooded lunar craters, creating the Lunar Maria o Now geologically dead o 17% of the surface is Lunar Maria o 83% of the surface is highlands, which are heavily cratered Mars o 0.107 mass of Earth, 0.53 radius of earth, eccentricity of 0.1 o 1 year = 1.88 earth years; 1 day = 24 hours 39 minutes o mainly rocks and minerals o habitat like an Earth desert o liquid H2O once present  now dried up riverbeds o giant volcanoes, huge canyons, polar caps o atmosphere is 90% CO2 o seasonal winds create huge dust storms o two moons are Phobus and Deines, which are captured planeteismals o inclination at 23.45 degrees  seasons Jupiter o 5.2 AU from the sun o mass is 318x mass of earth, density is 1.33 g/cm^3 o mostly hydrogen and helium o ammonium sulfide clouds reflect red and brown light o Great Red Spot – storm twice as big as Earth, has existed for at least 3 centuries o Ammonia, highest and coldest layer, reflects white o 1 day = 10 hours o core of rock, metals, metallic hydrogen Moons of Jupiter o Io  Size of our moon  Most volcanically active object in the solar system  heat because of tidal heating, which refers to when orbit energy is dissipated as heat in either the surface or interior of a planet; moon creating friction from squishing and stretching o Europa  Covered by H2O ice  Twice as much water than on Earth o Ganymede  Largest moon in solar system  Clear evidence of geological activity  Tidal heating  Craters and smooth regions  Water/ice surface o Calisto  Cratered ice ball

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No tidal heating Magnetic field

Saturn o 9.54 Au from sun o mass 95x mass of earth, density is 0.71 g/cm^3 o mostly hydrogen and helium o core of rock and metals o giant and gaseous; has rings o 1 day = 10.5 hours o Cassini spacecraft currently studying it o Rings are divided into categories of A, B, and C o Rings are ice coated particles Saturn’s Moon Titan o Only moon with a thick atmosphere o Consists of mostly nitrogen with some argon, methane, and ethane o Methane and ethane rain o Rocks made of ice Uranus o Core of rock and metals, water, methane, ammonia o lower pressure  no metallic hydrogen o made of H/He gas and hydrogen compounds o inclination at 97.86 degrees because something hit it o 1 year is 84 earth years o albedo is 0.66 o 27 moons o blue because of methane presence; absorbs red light and reflects blue light Neptune o Core of rock and metals, water, methane, ammonia o Lower pressure  no metallic hydrogen o Mathematically discovered o Inclination at 29.56 degrees o 1 year is 164.8 earth years o Triton, its moon, rotates backwards  it has recent volcanic activity Comet – chunk of ice with some rock inside, originates from Pluto Asteroid – rocky leftover planetesimal, smaller are more common, Ceres is largest, smaller than 2km in diameter Meteoroid – smaller asteroid, from boulder to pebble size Meteor – flash of light of a meteoroid burning in the atmosphere Meteorite – meteor that hits Earth and survives Asteroid belt is between Mars and Jupiter No terrestrial planets past Mars because of the high magnetic field and gravitational pull in the outer solar system Two types of meteorites

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o Primitive – simple rock and metal, 4.6 billion years old, remnants of early solar system o Secondary/processed – pieces of the mantle or crust, parts of a planet, some iron, 100 million years old, volcanic activity Comets o Coma – comet itself, atmosphere that comes from heated nucleus o Tails  Plasma – gas escaping coma, pushed by solar wind  Dust – pushed by photons Oort cloud – comets on random orbits extending to about 50,000 AU Kuiper belt – closer than oort cloud, where Pluto is, comets on orderly orbits at 30-100 AU, in disk of solar system Pluto...