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This 3 page Class Notes was uploaded by Jocelyn on Saturday August 29, 2015. The Class Notes belongs to AST 1002 at University of Florida taught by Reyes, Francisco J in Summer 2015. Since its upload, it has received 153 views. For similar materials see Discover the Universe in Science at University of Florida.
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Date Created: 08/29/15
Thursday August 27 2015 Discover the Universe Week 1 New Explorations In July 2014 The New Horizon Spacecraft was the first of its kind to reach Pluto resulting in the best resolution images thus far In August 2012 the Curiosity rover began to interpret the Martian soil A satellite of Jupiter known as Europa contains a sea of liquid water beneath its frozen crust A satellite of Saturn known as Titan is made up of hydrocarbons liquid water and liquid methane beneath the icy surface Currently the Cassini spacecraft orbits around Saturn studying Titan Charting the Heavens Chapter 0 Andromeda is the galaxy closest to the Milky way Essential Question What is our place in the universe Sizes and Distances in Astronomy 1 meter 1 yard 1 km 10quot3 m 062 miles 1 AU Astronomical Unit Distance from Earth to Sun 150000000 km 150 x 10A6 km AU measures distances within the solar system 1 light year Light year measures It takes light 14 seconds to reach Earth from the moon It takes light 8 minutes to reach Earth from the Sun The nearest star Alpha Centauri is 4 ly light years away Center of our galaxy is 26000 ly away Andromeda Galaxy is 2 x 10quot6 years IMPORTANT We see distant objects as they were in the past Ex when we see the nearest star we see it as it was 4 years ago Thursday August 27 2015 Examining the Sky Constellations are random configurations of m Some constellations 88 total have acquired names from heroes in myths or animals Although stars create constellations they are generally not actually close to each other in space Celestial sphere occurs when stars seem to be attached to a large sphere extending all the way around Earth simultaneously rotating from East to West This phenomenon is caused from Earth s movement from West to East Celestial equator is known to occur when the terrestrial equator is projected onto the celestial sphere North Celestial Pole has stars appearing around it with a long exposure image Celestial coordinates are generated by the projection of the terrestrial coordinate system onto the celestial sphere Right Ascension RA and Declination Dec or dec are known as the celestial coordinates rather than the terrestrial longitude and latitude mht Ascension is the time to rotate through a particular angle the angle is measured in hoursminutessec between 0 to 24 hours The reference 0 hours of RA is at the position where the celestial equator crosses the Ecliptic Declination is measured in the form of degrees north and south of the celestial equator much like that of latitude and Earth s equator How do we measure angles in the sky The moon and sun share the same angular diameter 05 degrees The moon is about 380000 km away but only 3300 km in diameter The sun is 150000000 km away and about 1400000 km diameter Earth s Rotational and Orbital Motion The Earth rotates on its axis every day amp orbits the sun once a year These actions create sidereal and solar days Solar day is the day we know as 24 hours one rotation of Earth relative to Sun Sidereal day is 23 hours 56 min one rotation of Earth relative to the stars Thursday August 27 2015 We see different stars and constellations at night during different months due to the dark side of the Earth facing different directions Zodiac includes a unique group of 12 constellations that lie in the same plane as the Earth s orbital plane around the Sun The Sun would move through these constellations over the year if we could see stars during the day Ecliptic is the path of the sun throughout the sky over the course of a year Motion of the Sun along the Ecliptic on the Celestial Sphere The sun crosses the celestial equator two times a year during the vernal equinox at March 21st and the autumnal equinox around September 21st The sun reaches its highest point in the sky when it crosses over the meridian around June 21 m is the point in the sky straight overhead Meridian is the circle that passes through the Zenith and the two celestial poles Seasons Seasons are opposites in North and South hemispheres The 235 degree tilt of the Earth on its rotational axis is the main reason for the seasons Another viewpoint is that seasons occur due to the angle illumination of the sun Colder temperatures in the winter are a result of the sun remaining lower in the sky throughout the day Procession of the Equinoxes The gravitational pull of the moon and sun on earth causes the earth s spin axis to precess very similar to that of a top spinning down This situation causes the celestial poles to point in different directions as the Earth precesses The Procession Period is approximately 26000 years
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