Topic IV: The Solar System & Universe

Earth’s Moon Phases of the Moon: the amount of the lighted portion of the moon that faces the Earth

Why do we have phases of the moon? Because of the moon’s revolution around the Earth (27.3 days)—the moon is in different locations in relation to the sun)

New Moon: (no moon) the entire lighted side of the moon faces away from the earth

Waxing Moon: the right side of the moon appears to grow (amount of the lighted portion facing Earth becomes greater)

Full Moon: the entire lighted portion of the moon can be seen from Earth

Waning Moon: the right side of the moon appears to get smaller (the amount of the lighted portion facing Earth gets less)

**it takes about 29.5 days for the moon to go through the phases (1 month) Moon Phase Animation

Why is there a dark (Far) side of the moon? Because the moon revolves at the same rate as it rotates Far Side of the Moon Animation

Eclipses of the Sun and Moon Lunar Eclipse: when the moon revolves into the shadow of the Earth—Earth blocks moon’s light **Full Moon Only!!!

Lunar Eclipse

Solar Eclipse: when the moon blocks out the sun—casting a shadow on the Earth **New Moon Only!!!

Solar Eclipse

We do not have eclipses every month because the Earth, moon, and sun are not perfectly lined up every month….

Tides Tides: the daily rise and fall of the ocean water Every coastal location receives 2 high tides and 2 low tides everyday 6hrs → 6hrs → 6hrs → 6hrs H L H L

Low Tide

High Tide

Why…. because of the gravitational pull of the sun and the moon! Daily Tide Animation

Remember….. Gravity is affected by 2 variables: Mass (↑ mass, ↑ gravity) Distance (↑ distance, ↓ gravity) **The moon is the primary cause of the tides because it is 400 times closer to the Earth than the sun (even though the sun is much bigger)

Spring Tides: when the sun and the moon act together to influence the tides (new & full moons) **Get highest high tide and the lowest low tide

Neap Tides: when the sun and the moon “fight” each other to influence the tides (quarter moons) **Get the lowest high tides and the highest low tides (not that dramatic of a change)

Spring & Neap Tide Animation

Why does the diameter of celestial objects appear to change throughout the year? Because of how close or how far the celestial object is towards Earth **the closer the object is to Earth—the bigger it will appear to be (and the opposite is also true)

How do planets revolve around the sun? Ellipse: oval shape of a planet’s orbit

Eccentricity: the mathematical way to show the “oval-ness” of an ellipse. **all eccentricity values will fall between 0 and 1 with 1 being a straight line and 0 being a perfect circle

ESRT’s—Page 15

**only careful measurements show that the Earth’s orbit is an ellipse—not a circle NOT EXACT

Why do objects revolve (orbit)? Gravity: force of attraction between a satellite and the object it revolves around **Object Needs to have mass

Inertia: the tendency of an object in motion to continue in motion in a straight path

**it is the balance between gravity and inertia that keeps a planet in orbit

So how does this balance happen? Orbital Speed: the speed of a planet around the sun →The speed of a planet changes as it gets closer to and farther away from the sun

Perihelion: when a planet is closest to the sun—orbital speed is fastest (our winter)

Aphelion: when a planet is farthest from the sun—orbital speed is slowest (our summer) ** “APART”

Planet motion as seen from Earth **because planets speed up and slow down in their orbit, they sometimes appear to go “backwards” as viewed from Earth Planet Motion

The Solar System Solar System: the sun (in the center) and all objects that revolve around the sun

Parts of the Solar System Planets (2 types) Terrestrial: Earth-like planets that have a small diameter, solid surface (high density), and are close to the sun

Mercury (no atmosphere, cratered)

Venus (thick CO2 atmosphere—high temp. because of green house effect)

Earth (O2 rich atmosphere, liquid water, sustains life)

Mars (red planet, thin atmosphere, cold temp.)

Jovian (Gas Giants): Jupiter-like planets that have a large diameter, low density, rings, and are far from the sun

Jupiter (largest planet)

Saturn (extensive ring system)

Uranus (really, this time)

Neptune

ESRT’s—Page 15

Asteroids: small rocky bodies that orbit the sun (asteroid belt: millions of asteroids concentrated between Mars and Jupiter)

Moons: natural satellites that orbit planets (a satellite is anything that orbits something else)

Comets: dirty snowballs that orbit the sun in a VERY ECCENTRIC Orbit (see the tail because the sun heats the comet)

Meteors: very small (pebble) solid fragments that orbit the sun **sometimes they enter the Earth’s atmosphere and burn up—shooting stars

Meteorites: meteors that hit the Earth’s surface and create a crater—Impact Event

Stars—Including our Sun Stars: large ball of gas that produces tremendous amounts of energy **the Sun is the star nearest to Earth—which is why it looks big (the only star in our solar system)

Nuclear Fusion: energy source for all stars—nuclei of smaller elements combine to make larger ones H + H He + Energy

Classification of Stars stars are classified by comparing their luminosity (brightness) and their temperature (color)

Pg. 15 .

Main Sequence: stars that have an average size and temperature (90% of all stars fall into this category—including the sun)

How do stars form and evolve? Originate from clouds of gas and dust—pressure causes fusion (nebula)

Orion Nebula Orion Nebula

Star Evolution: Gas → Formation → Main Sequence → Giants → Dwarfs (protostar) Super Nova (exploded star)

Our Sun: Sunspots: dark patches that disappear and reappear at different places on the surface of the sun

Our Galaxy: Galaxy: collection of billions of stars, gas, and dust all held together by gravity

**our galaxy is called the Milky Way

Billions of stars make up galaxies and billions of galaxies make up the universe!

Universe Size—pretty amazing

Evolution of the Universe Universe: everything—size is incomprehensible About 10-17 billion years old About 25 billion light-years across

Big Bang Theory: explanation of how the universe started—still not proven Says that all matter and energy was concentrated into an area the size of an atom and then it exploded—matter went out in all directions

**universe is still expanding—objects are moving away from each other (this is true)

Evidence that the Universe is expanding Background Radiation: microscopic particles that are still in motion—can be picked up as static

Doppler Effect: “messing up” of sound or light waves as they move toward you **So what does this have to do with the Universe?

Page 14—ESRT’s

…lets look at light from a star Stars burn different elements—and each element is unique in the way it gives off light (aka: wavelength or spectral lines) Hydrogen—our Sun

But light from stars in galaxies moving away from us look different because their waves or spectra are “messed up”

Red Shift: movement of spectral lines of distant stars towards the red end of the electromagnetic spectrum—moves away from Earth (longer wavelengths)

Blue Shift: movement of spectral lines of towards the blue end of the electromagnetic spectrum—moves towards Earth (shorter wavelengths)