“Earth in Space” Astronomy Part II Video: Standard Deviants Astronomy - 24:39; How the planets were made - 7:17

I. Laws of Planetary Motion: 3 laws proposed by Johannes Kepler to explain the shape, velocity, and distance of a planet’s orbit. A. Planetary Period: the time it takes a planet to orbit (revolve) around the Sun. Video: orbit – 1:30

B. Kepler’s Laws: 1. First Law: the orbits of planets are ellipses around the Sun, with the Sun at one focus. a. eccentricity: a measure of how elliptical a planet’s orbit is. b. Eccentricity formula: Ecc.= Dis. Between foci length of major axis * eccentricity of “0” is a perfect circle * Eccentricity of “1” is a straight line Video: the perfect orbit – 7:23

2. Second Law: the line joining the Sun and a planet sweeps out equal areas in equal intervals of time. a. A planet’s orbital velocity changes with distance from the Sun. *closer to the Sun (perihelion) the planet’s velocity is greater. *further from the Sun (aphelion) the planet’s velocity decreases.

3. Third Law: the further a planet is from the Sun the longer its period of revolution. * The outer planet (green) will have a longer period than the inner (white) planet.

C. Energy Transformation in an Orbit: 1. Gravity: the force that keeps all satellites moving in their curved orbits. 2. Inertia: the tendency of an object in motion to stay in motion in a straight path unless acted on by an outside force.

II. Models of the Solar System: A. Geocentric Model: suggests that Earth is the center of the solar system. B. Heliocentric Model: The Sun is the center of the solar system. This model explained planetary motion. Video: Copernicus – 3:50

III. Planets of the Solar System: A. Inner Terrestrial Planets: contain rocky surfaces. 1. Mercury 2. Venus 3. Earth 4. Mars Video - Spin around solar system 15:07

B. Outer Jovian Planets: gas giants with low densities and thick atmospheres. 1. Jupiter 2. Saturn 3. Uranus 4. Neptune

Earth’s Moon

2. Contains no atmosphere (no weather) IV. Earth’s Moon: the only natural satellite that revolves around Earth. A. Moon Facts: 1. 1/6 the gravity of Earth. 2. Contains no atmosphere (no weather) Video: same side of the Moon - 1:29

B. Phases of the Moon: 50% of the Moon’s surface is always illuminated, as the Moon revolves around Earth we see varying portions of the lit surface. 1. It takes 29 ½ days to complete the cycle from new moon to new moon. 2. The Moon rotates at the same rate it revolves. Allowing us to only see one side of the Moon.

Same Side of the Moon

3. Moon Phases (remember right to left): a. waxing: as the moon fills in from new to full moon. b. waning: as the moon becomes less illuminated from full to new moon.

C. Ocean Tides: are a result of the moon’s gravitational forces on Earth’s water. 1. Spring Tides: when the moon, Sun and Earth are lined up. * Higher high tides and lower low tides. *occurs at new and full moon phases.

2. Neap Tides: occur when the Sun, moon and Earth form right angle. * Normal tidal ranges. *Occurs at 1st and 3rd quarter phases.

D. Eclipses: occurs when a celestial body is totally or partially hidden from view. Solar eclipse: when the Moon is between Earth and the Sun (New Moon). * This does not occur at every new moon.

2. Lunar Eclipse: can occur during a full moon phase 2. Lunar Eclipse: can occur during a full moon phase. Earth’s shadow is cast onto the moon. * Umbra shadow: total darkness *Penumbra shadow: partial darkness.

V. The Universe: created by an explosion, The Big Bang, and is composed of billions of galaxies. A. Order of Increasing Size: small-----Solar system Galaxy large------Universe

B. The Doppler Effect: proof that the universe is expanding B. The Doppler Effect: proof that the universe is expanding. A shifting of wavelength frequencies. Red Shift: objects moving away from Earth. Larger wavelengths shift to the red spectrum. 2. Blue Shift: objects moving towards Earth. Smaller wavelengths shift to blue spectrum. * BLUE TO YOU!!

C. Milky Way Galaxy: large disked shaped system with spiral arms containing billions of stars. 1. Our solar system is located on one of the arms.

The Milky Way Side View

D. The Sun: an average size star formed 5 billion years ago D. The Sun: an average size star formed 5 billion years ago. Composed mostly of hydrogen and helium formed by nuclear fusion. 1. Stars are classified based on their size and luminosity (brightness).

Video: The fate of our solar system – 7:11

Distance = (speed) (time); d = (v) (t) Astronomical Scales Distance to nearest star: Alpha (α) Centauri: 4 light-years 1 light-year (L.Y.) – distance light travels in one year’s time Distance = (speed) (time); d = (v) (t) 1 L.Y. = speed of light x one year 1 L.Y. = (186,000 mi/sec) x (31,500,000 sec) 1 L.Y. = (1.86 x 105 mi/sec) x (3.15 x 107 sec) 1 L.Y. = (1.86 x 3.15) x (105 x 107) 1 L.Y. = 5.86 x 1012 miles Dist. to α Centauri = 4 L.Y. = 2.34 x 1013 miles