Our Solar System Chapter 28. Formation of the Solar System 28.1.

Our Solar System

Chapter 28

Formation of the Solar System

28.1

Stars and planets form from interstellar cloudsThey appear dark because of dust blocking

out the lightThe light can cause it to glow, or even

become heatedStarts and solar systems are “born” this

way Collapse accelerates

The collapse of this cloud is slow, but it accelerates and becomes denser at the center

This collapse and spin results in a flattening at the equatorial plane

Matter condensesOur solar system may hav eformed this way when

temperature and pressure cause hydrogen to fuse into helium

The temperature differential allowed for different elements to concentrate in different areas around the sun This is why the inner planets are rocky and have a

higher melting point Outer ones are less dense and made of ice and gas

Much like coalescence, the planetesimals combined to get larger in many cases to become the known planets.

Gas giants formJupiter was the first to formIcy planetesimals combined to form itIts mass (gravity) caused it to collect

much of the debrisThe others formed the same way, but

Jupiter took most of the extraneous material

Terrestrial planets form the merging of planetesimals in the inner

portion of the diskMade of materials that resist vaporizationMost of the gaseous material and “smaller

stuff” consumed by the sun, hence fewer satellites.

DebrisAll of the “junk” left overSome became cometsSome ejected from solar system or destroyed

in collisionsThe asteroid belt between mars and Jupiter is

the rest

Initially the geocentric theory stated that everything moved around the earth.

Retrograde motion led astronomers to find a different explanation

The heliocentric model (Copernicus) put the sun at the center and planets in orbit around it.Proximity to the sun caused planets to

move at different speedsThis explained retrograde

Kepler’s Laws1st law is that planets move in elliptical orbitsThe sun was at 1 focusThe semi-major axis (half the length of the

major axis) is where we get the AU (astronomical unit) distance many distances are measured in This is more math that I want to get into!

The eccentricity of the orbit is how “squashed” the orbit is

2nd law is an equal area is swept out in equal amounts of time (although the orbital distance may be different)

3rd law he defined the size of the ellipse and the orbital period (year)

Gravity is the attractive force between 2 objects It is affected by mass and distance

Gravity is what determines the orbit planets follow

Newton’s explanation of gravity supported Kepler’s laws of planetary motion.

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The Inner Planets

28.2

these are the 4 inner planets similar densities to Earth solid rocky surfaces

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closest to the sun 1/3 Earth’s size no moons 2 Mercury Years is 3 Mercury days Atmosphere

O2 and Sodium replenished daily by the sun

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Surfacecovered with craters and plains the plains formed much like the maria on the

moon the craters are smaller with less ejecta

Interior the density suggests a dense core similar to the

Earth the magnetic field suggests its partially molten

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Has no moons the brightest planet because of

proximity and albedo 75% Thick atmosphere doesn’t allow for

direct observation probes and satellites have provided

radar images of 98% of the surface

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28.3

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These planets include: Jupiter, Saturn, Uranus and Neptune

All larger than Earth by 15-300 times

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The largest planet 1/10 of the sun and 11X Earth’s

Better than 70% of the planetary mass of the solar system

52% albedo Has a banded appearance “the great spot” is a storm that has

lasted for better than 300 years

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Density is relatively low for its sizeThe is because of it composition (H and He in gas

or liquid form. Rotation

Shortest day in the solar system about 10hrs This fast spin distorts the shape This also contributes to its banded appearance

Belts are low lying dark-colored cloudsZones are high light-colored clouds

MoonsMore than 60, but some are very small

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Mostly composed of ice and rock Gravity assist

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Second largest planet in the solar system

Atmosphere and interiorSlightly smaller than JupiterDensity less than water… it would float!

RingsMuch broader and brighter than other

planets’7 major rings made up of ringletsGravity keeps the rings in place

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Moons55 moonsTitan, the largest is bigger than Mercury

Odd among moons because of content with dense atmosphere and methane’s existence in 3 states

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4x larger and 15Xmass of the Earth Atmosphere

Bluish appearance cause by methane gasClouds are similar in appearance to the

surfaceLiquid surface with a small solid core

Moons and RingsAt least 27 moons and faint rings

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The rings are dark and almost not observed Rotation

Almost a top to bottom rotationPoles vacillate between 42 years of darkness and

light

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AtmosphereSmaller and denser than Uranus but 4XEarthSimilar in color to Uranus (twins??) but does have

some color variation on surfaceBelts and zones give it texture

Moons and Rings13 moons Triton being the largest

Triton has retrograde orbit Also has nitrogen geysers when heated by the sun Rings are invisible from Earth but exist

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