Pick up 2 packets.Draw on the back of your notes packet: 1. Your picture of the 8 planets

orbiting around the sun. What type of solar system is this called?

2. Your picture of how ancient people must’ve drawn the planets orbiting around Earth. Remember, they had to keep their observations of retrograde motion in mind! What is retrograde motion? What type of solar system is this called?

History of our Knowledge of the Solar System

EARLY IDEAS GEOCENTRIC UNIVERSE

Early Astronomers Separated Stars from

Planets▪ Planets movements

can be tracked because stars do not move.

Ptolmey: Geocentric Universe▪ Earth is the center of

the universe.▪ All the planets and

the Sun revolve around the Earth

Geocentric Model of the UniversePROBLEMS

1). Retrograde Motion A sudden

change in planetary motion

Planets switch from moving East to moving West

Very hard problem to solve

Scientists began looking for a better model of the universe/solar system.

http://www.youtube.com/watch?v=ln1fHZvRr8o

Retrograde Motion SolvedCOPERNICUS RETROGRADE MOTION

EXPLAINED

In 1543, he suggested a heliocentric model of the universe Sun centered Earth and all

other planets orbit the Sun

Why do we see planets moving backwards? Inner planets move

faster then outer planets around the Sun.

Earth will “pass” a slower moving planet▪ This planet appears

to move backward temporarily.

What is Eccentricity

ECCENTRICITY DETAILS

What is eccentricity? Ratio of distance

between the foci to the major axis.

Change in distance from the focus points; such as distance of a planet from the Sun. Planets are not always

the same distance away from the Sun.

http://www.youtube.com/watch?v=BIBz_GQDga0

The point in orbit when the planet comes nearest to the Sun = Perihelion

The point in orbit when the planet is farthest from the Sun = Aphelion

Kepler’s Laws

1ST LAW ASTRONOMICAL UNIT

Most planets orbit the Sun in an elliptical shape More oval like Earth being the

exception Earth believed to move

between an elliptical orbit and a circular orbit every 100,000 yrs or so.

Planets orbit while staying centered around 2 points. Sun is one point

How we measure the average distance between the Sun and planets. Sun to Earth = 1

astronomical unit (AU)

Kepler’s Law

Planets sweep out equal areas in equal times.

Perihelion/Aphelion on Earth

Gravity

In the late 16th century early 17th century Galileo was working with gravity.

Performed experiments dropping objects off the Tower of Pisa and rolling balls down inclines

Galileo found Gravity

accelerates the fall of all objects at the same rate.

Air resistance causes lighter objects to fall more slowly.

Gravity

SIR ISAAC NEWTON BASICS

1687 Newton published his theory of universal gravitation. Also called the inverse

square law This theory helped

discover Neptune. Watched Uranus’s

movements▪ Something large was

affecting the movements of the planet.

Two objects attract each other Depends upon

their mass AND the distance between them.

Law

This knowledge of gravity produced the law of universal gravitation.

The larger the objects (m) the stronger the force of gravity between them.

The farther apart the objects (d) the weaker the force of gravity. Distance squared

weakerG = Constant 6.6726 X 10-11

Astronomy: Part 2 Stars

3/7/13

Fact or Fiction

Stars twinkle in the night sky Twinkle: Change in Brightness

Beginning of A Stars Lifecycle 1). Interstellar

Cloud/Nebulae Big Cloud of Gas

and Dust

Once enough gas has collected the nebulae will condense forming a….

2). Protostar: Pre-star

As the protostar continues to condense it will heat up until it hits Critical Mass and…

3). Nuclear fusion begins Now we have a real

main sequence star. ▪ Main Sequence =

Stable

What is a Star?

Star = A cloud of gas, mainly hydrogen and helium with a core so hot and dense that that nuclear fusion can occur. Very Common

Purpose/Jobs 1). Provide Light▪ Heat Energy▪ Warms Planet Earth

2). Nuclear fusion within stars converts light elements into heavier ones

Nuclear Fusion

Create new more complex elements Without these life

would not be able to form

Will continue in a star until no heavier element can be produced Iron is the ultimate

stopping point

Helps balance out the force of gravity trying to act on stars

When fusion stops, gravity will win and cause the star to collapse. This is when a star

begins to die.

Important Star Qualities

Three Main Characteristics1. Brightness/Magnitude

1. Light releasing capacity

2. Color1. Determines Temperature

3. Size1. Determines means of Death

Stars Magnitude/Brightness

MAGNITUDE Tells us how luminous the star

is/ How much energy is being produced in the core

Astronomers rate the magnitude of a star with a scale that gives brighter stars a low number and dim stars a higher number. Each whole number on this

scale is 10 times dimmer than the previous number.

The brightest star the night sky is Sirius. magnitude of -1.46 it is almost 15 times

brighter than a star with a magnitude of zero.

Stars with a magnitude of 8 or more are too dim to see with the naked eye.

Color of Stars Stars are identified by

their color, which indicates their temperature.

They are divided into what are known as spectral classes.

These classes are O, B, A, F, G, K, and M.

Class O stars are the hottest and are blue in color.

The coolest stars are identified as class M and are red in color.

Star Size

Determines the length of a star’s life Large Stars = Burn Out Quickly

Small Stars = Use fuel more slowly▪ Around for much longer periods of time.

Star size also determines the death route a star will take.

The Death of an Average Size Star

Fusion of Hydrogen Stops No longer a main sequence star

Red Giant  Large star that is reddish or

orange in color Reaching sizes of over 100 times

the star's original size. Late phase of development in a

star's life ▪ Hydrogen has been exhausted and

Helium is being fused. ▪ This causes the star to collapse,

raising the temperature in the core. ▪ The outer surface of the star expands

and cools, giving it a reddish color. This phase will continue until the

star completely runs out of fuel

Planetary Nebulae When nuclear fusion stops Stars blow away their outer

layer of atmosphere

White Dwarf Remaining core of the star

▪ Present after atmosphere has blown away

Still very hot so it glows white until it cools off

Black Dwarf Cooled off core of a star

Death of A Massive Star Fusion of Hydrogen Stops

No longer a main sequence star

Red Supergiant  Extremely large star that is

reddish or orange in color Reaching sizes of over 1000

times the star's original size. Late phase of development in a

star's life ▪ Hydrogen has been exhausted and

Helium is being fused. ▪ This causes the star to collapse,

raising the temperature in the core. ▪ The outer surface of the star expands

and cools, giving it a reddish color. This phase will continue until the

star completely runs out of fuel

Betelgeuse in Orion is an example of a red supergiant star.

Death of A Massive Star Continued Supernova

 violent explosion ejects most of its

mass. often briefly

outshines an entire galaxy▪ fade from view

over several weeks or months

Neutron Star If the remaining mass of the star is

about 1.4 times that of our Sun, the core is unable to support itself and it will collapse further to become a neutron star.

The matter inside is compressed so tightly that its atoms are compacted into a dense shell of neutrons.

Black Hole If the remaining mass of the star is

more than about three times that of the Sun, it will collapse so completely that it will literally disappear from the universe.

What is left behind is an intense region of gravity called a black hole.

Planet Types

TERRESTRIAL PLANET GAS PLANET

Inner Four Planets Closest to the Sun Mercury, Venus,

Earth, and Mars

Close to the size of Earth

Solid, Rocky Surfaces

Outer four Planets Farthest from the

Sun Jupiter, Saturn,

Uranus, Neptune

Larger

More Gaseous

Lack Solid Surfaces

How Do Scientists Know How Our Solar System Formed?

Earth Based Studies Use of telescopes

in all wavelengths of the electromagnetic spectrum.

Data From Probes

Scientists Examined 1). Why the

planets are so different.▪ Especially Outer

and Inner Planets 2). Asteroids,

Meteorites, and Comets.

Formation of Our Solar SystemINTERSTELLAR CLOUDS

Huge Clouds of Dust and Gas in Space

Made of Hydrogen and Helium

Form Stars and Planets

These Interstellar Clouds usually look dark because the dust blocks light. Like Smog Stars behind this

cloud can’t shine through it.

Formation of our Solar System

INTERSTELLAR CLOUD

But….Sometimes the light from stars within the cloud causes these interstellar clouds to glow.

Formation of our Solar SystemLOCATION

There are many interstellar clouds found within our Milky Way Galaxy. We look for high

amounts of gas and dust.

When enough gas and dust is present, scientist think these interstellar clouds will condense because of gravity. Can form a star or

planet

Formation of our Solar System

COLLAPSING INTERSTELLAR CLOUD

Cloud begins collapsing slowly.

The smaller it gets the faster it begins to collapse and spin

This spinning motion with eventually form a rotating disk with a very dense center (core).

Formation of our Solar System

Scientist believe that one huge interstellar cloud called the solar nebula formed the Sun and all the planets.

The Sun formed first in the center of this cloud. Fits with why our Sun is

the brightest most dense thing in our solar system.

In the center of the cloud it was the hottest

On the edges of the cloud it was the coldest

Formation of our Solar System

SO WHAT?

This difference in temperature as the solar system cooled caused materials to condense and be located in very narrow regions of the solar system

This is why we see inner planets and outer planets have such different composition.

Development of Planets

Once these materials condense out they begin to collide and stick together.

Keep growing larger until they form planetesimals Objects 100’s of km

in diameter

To produce planets, planetesimals must collide and stick together

Development of PlanetsOUTER PLANET FORMATION

1st planet of the gas to form was Jupiter This is why Jupiter is the

largest. Had the most materials to

build with Then Saturn and the rest

of the gas giants formed▪ Not as large because Jupiter

hogged most of the materials; gas, dust, and ice to make itself.

Leftovers became Moons

Development of PlanetsINNER PLANET FORMATION

Inner planets were forming from the collision of planetesimals. Made of very

different things

Sun took all the gas and floating debris away from the inner planets. Why they are

rocky and dense Why Moons are

rare for inner planets.

Space Rocks 101

ASTEROID

Leftover pieces of Planetesimals

These were never planets

Asteroids can collide and break apart.

Space Rocks 101

METEOROID METEOR

When an asteroid or any space material falls toward Earth and enters Earth’s atmosphere.

The streak of light produced when a meteoroid burns up in Earth’s atmosphere.

Space Rocks 101

METEORITE

When a space object impacts Earth

Occurs when all of the meteoroid does not burn up in Earth’s atmosphere

Meteor Crater: Arizona

Gosses Bluff, Australia

Space Rocks 101

COMETS

Small icy and rocky bodies with a highly eccentric orbit around the Sun.

When Earth is in the way of a comet’s orbit we see a meteor shower