**Some parts of these may contain exact wordings from the lesson. Use word for word at your own risk.**

~The Sun

-hot ball of helium and hydrogen
-Sun’s average diameter is 1,391,980 kilometers (10x bigger than the largest planet)
-Sends the most light - 400,000x as much as the moon and 12.5 billion x as much as Sirius
-surface temp 10,000 degrees F
-Sol is Latin for Sun, "solar system" derived from this

~The Sizes of the Planets

-strength of magic depends on size
-in increasing order of distance from the sun: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune

~Inner Planets

-Mercury, Venus, Earth, and Mars
-separated from outer planets by asteroid belt
-rocky surfaces
-reflect just as much magic to us because they're closer
-at the best of times, Venus reflects more magic to us than any of the outer planets, and Mars and Mercury reflect more than two of them
-Mercury: Innermost, no moons, mountains, plains, craters, thin atmosphere, made up mostly of oxygen, sodium, and helium. Sunlit side can be 427 degrees C, and temp can be as low as -220 degrees C when sun is down
-Venus: no moons, covered by thick sulphuric acid clouds, not many small craters, exerts 92x as much pressure as earth's atmosphere, extremely hot night and day. 462 degrees C , cooler on Maxwell Montes (tallest mountain) - 380°C
-Earth: Home planet, 1 moon - aka "Luna or "Selena", tidal forces of earth cause the same side of the moon to face us at all times
-Mars: Also has mountains, plains, and craters. Looks reddish because of iron oxide that covers most of the planet and is blanketed with dust, some parts look darker bc they're made of different types of rocks. No liquid water, but there is some under the surface, poles covered in frozen water. Atmosphere exerts 100x less pressure than earth, creates dust storms often. temp ranges from -143°C to 35°C, two moons: Phobos and Deimos. Both tidally locked

~The Outer Planets

-Jupiter, Saturn, Uranus, and Neptune
-All are made of gas, no surface - aka "gas giants"
-huge
-all have rings, though only Saturn's can be seen through a telescope
-Jupiter: clouds of ammonia crystals alternating between darker and lighter colours, The Great Red Spot is a vortex, planet is made of mostly hydrogen with a smaller amount of helium and some trace gases. Temp outside planet: -160°C, temp inside planet: hotter than sun. Emits radiation, has 79 known moons (12 discovered in 2018). four largest moons, Io, Europa, Ganymede, and Callisto, are called the Galilean moons, as they were discovered by Galileo
-Saturn: mostly made of hydrogen and helium, vortex at each pole, famous for rings(made up of chunks of frozen water), rings 20 m thick, extend from 6,630 to 120,700 km outwards from the planet’s equator. Galileo called them ears. Temp: -185°C. 89 known moons (largest is Titan).
-Uranus and Neptune: Can't be seen with naked eye, Neptune has a dark spot. Very cold. Uranus has 27 moons, Neptune has 14. Neptune's largest moon, Triton, is 100x as large as all Neptune's moons combined. Primarily made of hydrogen and helium, but also have a fair amount of ice, namely water, ammonia, and methane ice. Sometimes called 'ice giants'.

~The Motion of Planets
--Revolution of Planets Around the Sun

-appears from Earth that planets revolve around earth
-Ptolemy (Greek astronomer) studied this
-Aristarchus of Samos believed Sun was the center of universe
-model is termed heliocentric
-Polish astronomer Nicolaus Copernicus wrote a book expounding the same model, which was published in 1543
-wasn't accepted right away, though Galileo supported it
-Catholic church forced Galileo to recant under threat of torture
- Venus probes the geocentric model incorrect bc if Venus were always closer than the Sun to Earth than the Sun, it would only ever be in the crescent phase
-Copernicus introduced epicycles
-Johannes Kepler studied Brahe’s published observations and proposed an alternative heliocentric model taking them into account.
-Kepler's First Law: A planet revolves around the Sun not in a circle but in an ellipse, which is like a flattened (or stretched out) circle, and the Sun isn’t in the middle of the ellipse but off to one side
-Kepler's Second Law: An imaginary line between the Sun and any planet sweeps out equal areas in equal amounts of time (a planet will speed up as it approaches the Sun and slow down as it recedes)
-Kepler's Third Law: If you divide the square of the time it takes for any planet to revolve around the Sun by the cube of the average distance from the planet to the Sun, you get the same answer no matter which planet you choose (planets that are closer to the Sun move faster than planets that are farther away)
-Mars and Mercury don't travel in circles, and the sun is not the exact center
-44 days is half the time it takes Mercury to revolve around the Sun, and yet the planet has moved just under half way around its orbit, as it is farther away from the Sun during this half
-While Mercury moves almost a full half-revolution around the Sun in this time period, Venus only moves about a quarter, and Mars even less, illustrating the Third Law
-Chart:
Name/Definition:
Orbit/Path of a planet around the sun or moon around a planet
Aphelion/farthest distance between planet and sun
Perihelion/nearest distance between a planet and sun
Apogee/farthest distance between Moon and Earth
Perigee/Nearest distance between Moon and Earth

-Length of a planet's orbit: aphelion+perihelion
-Eccentricity of a planet’s orbit (amount by which the Sun is off centre) = (aphelion - perihelion)/length
-Newton's 3 Laws of Motion:
-1. An object remains at rest or continues to move in a straight line at a constant speed unless acted upon by an outside force.
-2. The force required to make an object change its speed and/or direction of motion is equal to the mass of the object multiplied by the rate of change.
-3. f one object exerts a force on a second object, then the second object will exert the same amount of force on the first one, but in the opposite direction.
-an unsupported object falls to the ground instead of floating in the air because a force acts on it
-Moon moves fast enough around earth that instead of hitting earth, it falls around it
-Law of Universal Gravitation: Every body attracts every other body (gravity)
-the more mass a body has, the more it exerts on others
-the farther apart two objects are, the smaller the force will be by an amount equal to the square of the distance between them, and that’s why planets that are closer to the Sun move faster than planets that are farther away
-formula for amount of force 2 objects exert on each other:
Mass object 1*Mass object 2/Distance between objects*Constant
Or, the mass of object one times the mass of object 2, divided by the distance between objects, times the constant

~The Rotation of the Planets

-planets rotate on an imaginary line (the axis)
-equator
-Astronomical Unit (AU): 149,597,870.7 kilometers (92,955,807.3 miles).
-Distance between sun and earth is about 1 AU
-Link to table: https://imgur.com/a/myUB2jq
-Venus and Uranus are inclined more than 90 degrees from orbits, so they rotate backward!

~Assignments

-Mandatory Quiz (will not yet be tested on the harder material)