Assignment 1 The tilt of Earth s axis causes different portions of Earth to receive more or less Circumpolar Seasons Stars that are always visible in the sky direct sunlight at different times of year If we have a new moon today we will have a full moon in 2 weeks Can not see a new moon in the sky because it is too near the Sun Lunar eclipse occurs only during a full moon A typical galaxy is a collection of a few million to a trillion or more stars bound together by gravity Universe Big Bang The universe is expanding means the average distances between galaxies are increasing The sum total of all matter and energy The event that marked the beginning of the expansion of the universe with time Age of the Universe is approx 14 billion Light year is a unit of distance Observable universe current age of the universe that portion of the universe that we can see in principle given the Distance of the Earth to the Sun is about 15 meters Distance of the Earth to the Moon is small enough to fit on your hand Using a scale of 1 to 10 billion on which Earth is about the size of a ballpoint and located about 15 meters from a grapefruit size Sun the distance to the nearest stars is more than 4 000 kilometers about 2 500 miles The number of stars in the Milky Way Galaxy is approximately The number of stars in the Milky Way Galaxy is approximately a few hundred billion the avg distance between the sun and moon about 150 million KM AU Ecliptic Plane The universe is about 14 billion years old so we cannot observe objects more than about The plane of Earth s orbit around the Sun 14 billion light years away The total number of observable stars is about the number of grains of sand on Earth According to present understanding the early universe contained only the elements hydrogen and helium Stars produced all other elements including carbon oxygen and other major ingredients of life Galaxies recycle material from one generation of stars to the next and without this recycling we could not exist Except for hydrogen all the elements of life were produced by stars and scattered into space when the stars died Without galactic recycling these elements would have dispersed into the expanding universe rather than being available to build planets and life around later generations of stars Our solar system is about 1 3 the age of the universe Our solar system is located about half way between the center and the edge of the visible disk of the galaxy Astronomers infer that the universe is expanding because distant galaxies all appear to be moving away from us and the more distant ones are moving faster Hubble s great discovery Dark matter move with galaxies and clusters but they do not move faster than them Your speed of rotation is faster if you live near the equator than if you live near the north pole The fact that the universe was expanding lead us to the idea of a Big Bang Elements such as carbon and oxygen came from nuclear fusion in massive stars The Sun began to shine as a full fledged star when nuclear fusion began inside of it when our solar system was born 4 5 billion years ago The earth was formed around early September Life arose in September the nearest star besides our Sun about 2 5 million light years away Alpha Centauri a star forming cloud located outside our solar system Orion Nebula The disk of the milky ways is about 100 000 light years in diameter The distance to the Andromeda Galaxy is about 2 5 million light years The distance between the center of the Milky Way to us is about 28 000 light years away From farthest to nearest Andromeda star on the far side of the Milky way star on the near side of the Milky way Orion nebula alpha centauri Pluto Sun The distance between Alpha Centauri and Earth is about 4 light years A light year is 60 000 times bigger than 1 AU Assignment 2 a half circle extending from your horizon due north through your zenith to Ecliptic Meridian the point directly over your head the path the Sun appears to trace around the celestial sphere your horizon due south divides the sky into eastern and western halves Zenith We describe a location on Earth s surface by stating its latitude and longitude The altitude of the north celestial pole equals your latitude The cycle of Moon s phases takes about a month Earth s rotation defines a day Earth s orbit defines a year Earth s cycle of axis precession takes about 26 000 years The moon always show the same face to Earth bc the moon rotates once in the same amount of time it takes the moon to orbit Earth once the 18 year period over which the pattern of eclipses repeats Lunar eclipses can occur only during a full moon Saros cycle Apparent Retrograde Motion Over many days or weeks the planet moves westward relative to the stars rather than the usual eastward relative to the stars the slight back forth shifting of star positions that occurs as we view the stars form different positions in Earths orbit of the Sun direct proof that Earth orbits the Sun Stellar Parallax An angle of 1 arc second is less than the thickness of a human hair held at arms length The altitude of the north celestial pole in the local sky is equal to your latitude so traveling north to a higher altitude means the North Star will move higher in your sky The altitude of the south celestial pole is equal to your latitude therefor if you see the Facing north the sky appears to turn counterclockwise in 6 hours the sky will turn south celestial pole at altitude 40 degrees then you must be located at latitude 40 degrees south of the way around a full circle so all the stars will appear to have moved 90 degrees counterclockwise around the north celestial pole If the big dipper is close to the northern horizon and the north star is above it in 6 hours the big dipper will appear to the right of the north star which is 90 degrees counterclockwise from its current position Some constellations are only visible at certain times in the year because our view depends At the equator the Sun passes through the zenith just twice each year at noon on The Sun s path as viewed from the equator is highest in the sky on the spring and on where the Earth is located in its orbit around the Sun fall equinoxes the spring and fall equinoxes If Earths axis tilt was greater than its current 23 5 degrees then Polaris will not be our north star and the region where the Sun does not rise on the winter solstice will be larger farther south summer and winters would be more severe the length of
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