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ASTR 111

Astronomy Unit 3 -circle can be divided into 360 degrees, each degree into 60 minutes of arc, and each minute into 60 seconds of arc -the symbols (°, ', '') are used -Galileo Galilei-made basic investigations into physical motions and was among the first to use a telescope for astronomical observations -Heliocentric theory- the earth orbits the Sun -Linear measure is the straight-line distance between two points -Measured in meters or kilometers -Angular measure is a measure of the difference in direction between two points as seen from a specified third point -Measured in degrees, minutes, and seconds -The order of the planets -My Very Energetic Mother Just Served Us Noodles Planet as defined by the IAU -The orbit must be circular enough not to cross the orbit of another planet. - A planet must also have enough mass to become nearly spherical. - And a planet must be able to sweep other small astronomical objects out of its orbital path. -Opposition when a planet is nearer to the Earth than to the Sun -Conjunction- when a planet is nearer the Sun than Earth -Astronomical Unit (AU) is the average distance of the Earth from the Sun: -1 AU = 1.5 × 10 ^11 meters -Synodic Period- Ex: the time between full moons -Sidereal period- interval with respect to the stars. Perihelion- When the planet is closest to the Sun -When the planet is most distant from the Sun. Kepler’s three laws: 1. Orbits are ellipses with Sun at one focus. The shape of a planet’s orbit. 2. Line joining planet and Sun sweeps out equal areas in equal times. How a planet moves in its orbit. 3. Squares of sidereal periods are proportional to cubes of semi-major axis The relation of the average speed to the size of the orbit. Astronomy Unit 4 -radio telescopes are reflectors -focal length of a lens or mirror is where the image of a distant object falls - ligh
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