Scale of the Universe:

1 Astronomical Unit (AU) is...

Scale of the Universe:

1 Lightyear (LY) is...

The distance light travels in a year

The night sky:

Constellations

Stars the form the same pattern every night 

Models of the Universe:

Ptolemaic System

Copernican System

earth-centered universe, simpler, perfectly circular orbits, explains retrograde motions of planets, explain phases of Venus

Kepler's Laws 

1.) Planet orbits a sun in an ellipse with the sun at one focus 

2.) A planet sweeps out equal areas in equal times (ie moves faster when near sun)

3.) Square of period, proportional to the cube of the average distance from sun (ie planets further away from sun take longer to make one orbit) 

Newton's Laws

Masses move forever in a straight line until acted on by force. Force= mass x acceleration. Any force on an object, it produces a reaction force the same amount but in reverse direction 

Universal Law of Gravity

Newton figured out that the same force that makes an apple fall is what keeps a planet moving. 

Galileo

Developed a refracting telescope, phases of venus, jupiter's moons, craters on moon, and sun spots. 

Phases of the Moon:

Moon 

Tidally locked with Earth because of how it was formed. 

Tides

Spring Tides: Strong tides because moon and sun on opposite sides. 

Neap Tides: Lunar Eclipse, umbra and penumbra 

Terrestrial Planets:

Mercury

no atmosphere, very hot, then very cold, caloris impact basin, stretch marks from shrinkage, ray craters. Ice on Mercury inside crater at the poles that are always in shadow

Venus 

Earth

Similar to Venus, but only liquid water and life

Mars

atmosphere 1/100^th of the earth, CO₂, core shutdown --> mo magnetic field --> Solar wind scours away the atmosphere. Water did exist on mars, evidence of rivers and alluvial fans. 

Olympus Mons 

largest volcano in the solar system

Mercury, Moon, Mars

geologically dead, cratered. No Resurfacing (unless by impact)

Venus, Earth

Geologically active (quakes, resurfacing)

Outer Planets:

Jupiter

Largest in Solar System, if larger would be a star, hydrogen and helium atmosphere, huge magnetic field. Internal heating source, great red spot, banded by structure of atmosphere, uneven heating b/c rotation, coriolis effect, many moons 

Saturn

2nd largest, density low, would float on water, large ring system, ring formation. Probably formation by collision of moons. Shephard moons, give rings their banded structures.

Ice Planets:

Uranus 

Bluish green, featureless atmosphere, no internal heating. Axis tilted on its side. Rocky core, slushy ice mantle, hydrogen, helium atmosphere, methane reflection of sunlight gives its colour 

Neptune

Ice giant, 1000 mph winds, hydrogen/helium core, slushy ice mantle. (All outer planets have very large, thick atmospheres, all have a ring system [even if very faint])

Moons of the Solar System:

Jupiter's Moons 

-Inner Io being tidally squeezed --> very volcanic 

- Europa: Icy moon with 105 mile thick oceans underneath, may harbor life 

Saturn's Moon

Titan thick methane haze and atmosphere. Liquid methane oceans, rivers, rain. Use oxygen "fuel" tank to start a campfire

Asteroids

Rocks left over from creation of the solar system, some rocky, some metallic, others conglomerates. Asteroid belt and Kuiper Belt 

Comets

Dirty snowballs with highly elliptical orbits. Oort cloud origin. 

Heavy Bombardment 

Impacts in early earth happened all the time keeping surface molten. Most objects are already impacted or Jupiter flung them out of solar system. We dont have impacts on that scale anymore

Light is an Electromagnetic wave 

-continuous spectrum: smear of light

- Atomic Emission Spectrum: coloured lines (direct light from clouds)

- Atomic absorption Spectrum: Black lines (what happens when trying to look at star but cloud blocking)

Stars 

- Doppler shift going away (red shifted), going towards (blue shifted)

- Light interacts with matter: Transmission, reflection, absorption, emission

- Temperature: how much energy is stored in an object 

- Blackbody Curve: Relates the temp to the luminocity of an object 

- Structure of atoms: Protons, neutrons, electrons. Most mass at the center of an atom, atoms mostly empty space

Four Forces of Nature

(from strongest to weakest) 

1. Strong Nuclear: holds the nucleus together

2. Weak Nuclear: Responsible for radioactive decay

3. Electromagnetic: attracts and repels, so screens out over large distances

4. Gravity: much weaker than other forces; however, despite being weak, it dominates over large distances 

Hydrostatic Equilibrium

Stars live in balance between gravity and pressure. The hydrogen gas obeys the ideal gas law

Distance 

- 3 ways to measure: parallax method, cepheid variables, and type Ia Supernova

- Distance=1/parallax angle 

-Spectral Class: OBAFGKM (o-type stars how, m cool)

- Spectral Types (0-9) example G2 is the spectral type of our sun

- Luminocity Class: I Supergiant, III Giant, V Dwarf

- Keplers third law used to find mass of stars if we know the period and orbital radius

- Stellar Lifetimes: Lifetime equals mass divided by luminocity.