Chapter 1
Feb 23, 2016
Chapter 1. a stro1010-lee.com. Survey of Astronomy. [email protected]. Chapter 1. a stro1010-lee.com. Survey of Astronomy. [email protected]. Chapter 1. Astronomy -- Study of the Universe Universe -- everything that exists. Solar System Planets Moons Asteroids Comets - PowerPoint PPT Presentation
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Astronomy -- Study of the UniverseUniverse -- everything that exists
GalaxyThe Milky Way is our GalaxyStarsOpen Star ClustersGlobular Star ClustersNebulaeSunSolar System
Solar SystemPlanetsMoonsAsteroidsCometsOther debrisEarth/Moon System
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Subtend
When an object just fills an angle it subtends that angle.
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Degree (of arc) = 1/360 Circle
Minute (of arc) = 1/60 of a Degree
Second (of arc) = 1/60 of a Minute
Hour (of arc) = 360/24 = 15 degrees
Angular Units
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OUR CODE
The Earth and the entire Universe obey a single set of Laws
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Scientific Theory and the Scientific Method
Scientific theories:
must be testable
must be continually tested
should be simple
should be elegant
Scientific theories can be proven wrong, but they can never be proven right with 100% certainty
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Scientific Theory and the Scientific Method
• Observation leads to theory explaining it
• Theory leads to predictions consistent with previous observations
• Predictions of new phenomena are observed. If the observations agree with the prediction, more predictions can be made. If not, a new theory can be made.
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Early Discoveries
Pre-historicSunMoonStarsConstellationsPlanetsMovement of the SkyPath of the SunMovement of the Moon
HistoricCyclic nature of the Universe ….. led to calendars Explanation of the phases of the MoonNCPCelestial EquatorExplanation of the seasons
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Earth’s Orbital Motion
Daily cycle, noon to noon, is diurnal motion – solar day
Stars aren’t in quite the same place 24 hours later, though, due to Earth’s revolution around Sun; when they are, one sidereal day has passed
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From season to season the stars that we see change. This is because of the motion of the Earth in it orbit. The ancients thought it was because the Sun moved around the Earth
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The 12 constellations that the Sun appears to move through during the year are called the zodiac; the apparent path is the ecliptic
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The Earth revolves around the Sun once each year causing the Sun to appear to move around the sky
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• Time from one vernal equinox to next is tropical year
• Combination of day length and sunlight angle gives seasons
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Precession: rotation of Earth’s axis itself; makes one complete circle in about 26,000 years
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The Terrestrial Coordinate System
Latitude is measured north and south from the equator
Longitude is measured east and west from the prime meridian
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Zenith is the point directly overhead
Meridian is the line from the north point through the zenith and on to the south point.
Horizon is the line on the sky made by the plane that is perpendicular to the vertical line from you to the zenith
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The Celestial Coordinate System
Referencepoints andplanes onCelestialSphere
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The Celestial Coordinate SystemRight Ascension (RA) or Hour Angle is measured from the point on the sky where the Sun is at the Spring Equinox
Declination (δ) is measured north or south from the Celestial Equator
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