Foundations of Earth Science

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The Nature of
the Solar System
Chapter 15 Lecture
Natalie Bursztyn
Utah State University
Foundations of Earth Science
Eighth Edition

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Explain the geocentric view of the solar system.
Describe how it differs from the heliocentric view.
Focus Questions 15.1

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2

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Ancient Greeks
Used philosophical arguments to explain natural phenomena
Also used observational data
Most held a geocentric view of the universe
“Earth-centered” view
Earth as a motionless sphere at the center of the universe
Stars on the celestial sphere
Transparent, hollow sphere
Celestial sphere turns daily around Earth
Aristarchus first to propose heliocentric (sun-centered) universe
Ancient Astronomy

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Ancient Astronomy

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Ancient Astronomy

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Ptolemaic system
a.d. 141
Geocentric model
To explain retrograde motion, Ptolemy used two motions for the planets
– Large orbital circles, called deferents, and
– Small circles, called epicycles
Ancient Astronomy

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Ancient Astronomy

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Ancient Astronomy

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List and describe the contributions to modern astronomy of Nicolaus Copernicus, Tycho Brahe, Johannes Kepler, Galileo Galilei, and Isaac Newton.
Focus Question 15.2

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Nicolaus Copernicus (1473–1543)
Concluded Earth was a planet
Constructed a model of the solar system that put the Sun at the center, but he used circular orbits for the planets
Ushered out old astronomy
The Birth of Modern Astronomy

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The Birth of Modern Astronomy

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Tycho Brahe (1546–1601)
Precise observer
Tried to find stellar parallax
The apparent shift in a star’s position due to the revolution of Earth
Did not believe in the Copernican system because he was unable to observe stellar parallax
The Birth of Modern Astronomy

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Johannes Kepler (1571–1630)
Ushered in new astronomy
Planets revolve around the Sun
Three laws of planetary motion
Orbits of the planets are elliptical
Planets revolve around the Sun at varying speeds
There is a proportional relation between a planet’s orbital period and its distance to the Sun (measured in astronomical units (AU’s)— One AU averages about 150 million kilometers, or 93 million miles)
The Birth of Modern Astronomy

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The Birth of Modern Astronomy

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Galileo Galilei (1564–1642)
Supported Copernican theory
Used experimental data
Constructed an astronomical telescope in 1609
Four large moons of Jupiter
Planets appeared as disks
Phases of Venus
Features on the Moon
Sunspots
The Birth of Modern Astronomy

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The Birth of Modern Astronomy

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The Birth of Modern Astronomy

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Sir Isaac Newton (1643–1727)
Law of universal gravitation
Proved that the force of gravity, combined with the tendency of a planet to remain in straight-line motion, results in the elliptical orbits discovered by Kepler
The Birth of Modern Astronomy

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The Birth of Modern Astronomy

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Describe the formation of the solar system according to the nebular theory.
Compare and contrast the terrestrial and Jovian planets.
Focus Questions 15.3

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Nebular theory
Planets formed ~ 5 billion years ago
Solar system condensed from a solar nebula
Most material collected at center as the hot protosun
Other material formed a flattened rotating disc
Matter in the disc cooled and collided forming planetesimals
Our Solar System: An Overview

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As the protoplanets formed, the materials that compose them separated
Dense metallic elements (iron and nickel) sank toward their centers
Lighter elements (silicate minerals, oxygen, hydrogen) migrated toward their surfaces
Process called chemical differentiation
Due to their surface gravities, Venus and Earth retained atmospheric gases
Due to frigid temperatures, the Jovian planets contain a high percentage of ices
Our Solar System: An Overview

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Our Solar System: An Overview

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Two groups of planets occur in the solar system
Terrestrial (Earth-like) inner planets
Mercury, Venus, Earth, Mars
Small, dense, rocky
Low escape velocities
Jovian (Jupiter-like) outer planets
Jupiter, Saturn, Uranus, Neptune
Large, low density, gaseous—gas giants
Massive
Thick atmospheres composed of hydrogen, helium, methane, and ammonia
High escape velocities
Our Solar System: An Overview

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Our Solar System: An Overview

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Our Solar System: An Overview

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Planetary Impacts
Occurred throughout history of solar system
Bodies that have little or no atmosphere
No air resistance to prevent impact
Smallest pieces of debris reach the surface
At high velocities, debris produces microscopic cavities on individual mineral grains!
Large impact craters result from collisions with massive bodies, such as asteroids and comets
Our Solar System: An Overview

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Our Solar System: An Overview

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Our Solar System: An Overview

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List and describe the major features of Earth’s Moon.
Explain how maria basins were formed.
Focus Questions 15.4

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General characteristics
Diameter of 3475 km (2150 mi)
Unusually large compared to its parent planet
Density
3.3 times that of water
Comparable to Earth’s crustal rocks
Perhaps Moon has a small iron core
Gravitational attraction is one-sixth of Earth
No atmosphere
Tectonics no longer active
Surface bombarded by micrometeorites
Gradually make the landscape smooth
Earth’s Moon: A Chip Off the Old Block

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Consensus is that the Moon formed as a result of a collision
Mars-sized body collided with semimolten Earth
~4.5 billion years ago
Some ejected debris thrown into orbit coalesced to form the Moon
Impact model
Consistent with Moon having
Proportionately smaller core than Earth’s
Lower density than Earth
Earth’s Moon: A Chip Off the Old Block

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Lunar surface
Two types of terrain:
Maria (singular, mare), Latin for “sea”
Dark regions
Fairly smooth lowlands
Originated from asteroid impacts and lava flooding
Highlands
Bright, densely cratered regions
Make up most of the Moon
Make up all of the “back” side of the Moon
Older than maria
Earth’s Moon: A Chip Off the Old Block

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Earth’s Moon: A Chip Off the Old Block

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Lunar surface
Craters
Most obvious features of the lunar surface
Ejecta
Occasional rays
Associated with younger craters
Earth’s Moon: A Chip Off the Old Block

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Earth’s Moon: A Chip Off the Old Block

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Lunar surface
Lunar regolith
Covers all lunar terrains
Gray, unconsolidated debris
Composed of:
Igneous rocks
Breccia
Glass beads
Fine lunar dust
Earth’s Moon: A Chip Off the Old Block

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Earth’s Moon: A Chip Off the Old Block

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Outline the principal characteristics of Mercury, Venus, and Mars.
Describe their similarities to and differences from Earth.
Focus Questions 15.5

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Mercury: The Innermost Planet
Smallest planet
Revolves around the Sun quickly (88 days)
Rotates slowly on its axis
Mercury’s day–night cycle lasts 176 Earth-days
Greatest temperature extremes: 173°C to 427°C
Resembles Earth’s Moon in that it has very low reflectivity, no sustained atmosphere, numerous volcanic features, and a heavily cratered terrain
Terrestrial Planets

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Terrestrial Planets

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Venus: The Veiled Planet
Orbits in a near perfect circle every 225 Earth-days
Rotates in the opposite direction of other planets
Rotates slowly: 1 Venus day is 243 Earth-days
Has the densest atmosphere of the terrestrial planets
97% carbon dioxide
Extreme greenhouse effect
Surface temperature averages about 450°C day and night
Surface is completely hidden by a thick cloud layer of tiny sulfuric acid droplets
Terrestrial Planets

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Composition probably similar to Earth’s
Weak magnetic field means internal dynamics must be very different from Earth’s
More than 1000 volcanoes >20 km wide identified
Terrestrial Planets

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Terrestrial Planets

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Terrestrial Planets

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Mars: The Red Planet
Fourth planet from the Sun
Half the diameter of Earth
Revolves around the Sun in 687 Earth-days
Surface temps range from lows of 140°C at the poles in winter to highs of 68°C at the equator in summer
Very thin atmosphere: 1% as dense as Earth’s
Consists of 95% carbon dioxide
Small amounts of nitrogen, oxygen, and water vapor
Terrestrial Planets

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Terrestrial Planets

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Two-third of Mars’ surface is cratered highlands
If Mars had abundant water, it would flow north, forming an ocean
Mars has some of the largest volcanoes in the solar system, including Olympus Mons
The dominant force of erosion is wind
Poleward of 30°, water ice is found within 1 m of surface
Terrestrial Planets

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Terrestrial Planets

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Summarize and compare the features of Jupiter, Saturn, Uranus, and Neptune, including their ring systems.
Focus Question 15.6

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Jupiter: Lord of the Heavens
Largest planet—very massive
2.5 more massive than combined mass of planets, satellites, and asteroids
Orbits the sun once ever 12 Earth years
Rapid rotation—slightly less than 10 hours
Banded appearance
Multicolored
Bands are aligned parallel to Jupiter’s equator
Generated by wind system’s rapid rotation
Great Red Spot
In planet’s Southern Hemisphere
Counterclockwise rotating cyclonic storm
Jovian Planets

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Jovian Planets

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Jovian Planets

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Three main cloud layers:
Warmest, lowest layer
Mainly water ice
Appears blue-gray
Cooler middle layer
Ammonium hydrosulfide droplets
Brown to orange-brown
Upper layer
Ammonia ice
White, wispy
Jovian Planets

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At least 67 moons
Four largest moons discovered by Galileo
Callisto—Outermost Galilean moon
Europa—Smallest Galilean moon
Ganymede—Largest Jovian satellite
Io—Innermost Galilean moon and volcanically active
Jovian Planets

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Jovian Planets

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Saturn: The Elegant Planet
29 Earth years for one revolution around the Sun
Similar to Jupiter in
Atmosphere
Composition
Internal structure
Most striking feature is ring system
Discovered by Galileo in 1610
Ring nature determined by Christiaan Huygens 50 years later
Jovian Planets

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Jovian Planets

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Other features of Saturn
Dynamic atmosphere
93% hydrogen and 3% helium by volume
Clouds composed mainly of ammonia, ammonium hydrosulfide, and water
Segregated by temperature
Large cyclonic storms similar to Jupiter’s Great Red Spot
Emits roughly twice as much energy as it receives
Must have an internal heat source
Jovian Planets

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Saturn’s Moons
62 known moons; 53 named moons
Vary significantly in size, shape, surface age, and origin
23 “original” satellites formed in tandem with parent planet
Titan
Largest Saturnian moon
Second largest moon in the solar system
Has a substantial atmosphere
Enceladus
Cryovolcanism – eruption of magmas derived from partial melting of ice
Jovian Planets

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Saturn’s Rings
Composed of small particles (mainly water ice, lesser amounts of rocky debris) that orbit the planet
Most fall into one of two categories of particle density
Thought to be debris ejected from moons
Origin is still being debated
Jovian Planets

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Jovian Planets

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Jovian Planets

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Uranus and Neptune: Twins
Uranus: The Sideways Planet
84 Earth years for one revolution
Rotates “on its side”
Rings
Large moons have varied terrains
Neptune: The Windy Planet
165 Earth years for one revolution
Dynamic atmosphere
One of the windiest places in the solar system
Great Dark Spot
White cirrus-like clouds above the main cloud deck
Jovian Planets

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Uranus’s Moons
Uranus’s five largest moons have varied terrains
Innermost was recently geologically active
Uranus’s Rings
Discovered in 1977 that Uranus had five rings
More recent observations indicate that Uranus has atleast 10 rings
Jovian Planets

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Jovian Planets

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Neptune’s Moons
14 known satellites
Triton
Largest Neptune moon
Cryovolcanism
Icy magma is a mixture of water ice, methane, and probably ammonia
Generate outpourings of ice lavas great distances across the surface
Occasionally produce explosive eruptions
Ice equivalent of volcanic ash
Neptune’s Rings
Neptune has five named rings
Two broad and three narrow
Jovian Planets

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Jovian Planets

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List and describe the principal characteristics of the small bodies that inhabit the solar system.
Focus Question 15.7

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Other solar system objects classified into two broad categories:
Small solar system bodies—including asteroids, comets, and meteoroids
Dwarf planets
Small Solar System Bodies

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Asteroids: Leftover Planetesimals
Small bodies that remain from the formation of the solar system
Most in asteroid belt between Mars and Jupiter
Some have very eccentric orbits
Many recent impacts on the Moon and Earth were collisions with asteroids
Irregular shapes
Small Solar System Bodies

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Small Solar System Bodies

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Small Solar System Bodies

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Comets: Dirty Snowballs
Loose collections of rocky material, dust, water ice, and frozen gases (ammonia, methane, and carbon dioxide)
Nucleus—small central body
1 to 10 km diameter
Frozen gases vaporize when near the Sun
Produces a glowing head called the coma
Some may develop a tail that points away from Sun
Originate in Kuiper belt or Oort cloud
Small Solar System Bodies

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Small Solar System Bodies

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Small Solar System Bodies

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Meteors, Meteoroids, and Meteorites
Called meteors when they enter Earth’s atmosphere
A meteor shower occurs when Earth encounters a swarm of meteoroids associated with a comet’s path
Called meteorites when they are found on Earth
Types classified by composition
Irons
Mostly iron, 5–20% nickel
Stony
Silicate minerals with inclusions of other minerals
Stony irons
Mixtures
Small Solar System Bodies

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Small Solar System Bodies

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Small Solar System Bodies

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Dwarf Planets
Orbit the sun
Essentially spherical due to their own gravity
Not large enough to sweep their orbits clear of other debris
Pluto’s diameter: 2370 km (1470 mi)
~1/5 Earth’s diameter
<1/2 Mercury’s diameter Eris (Kuiper belt object) Ceres (largest-known asteroid) Small Solar System Bodies © 2017 Pearson Education, Inc. Small Solar System Bodies © 2017 Pearson Education, Inc. Beyond Our Solar System Chapter 16 Lecture Natalie Bursztyn Utah State University Foundations of Earth Science Eighth Edition

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1

Define cosmology.
Describe Edwin Hubble’s most significant discovery about the universe.
Focus Questions 16.1

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Cosmology
Study of the Universe
Light-year
Distance light travels in one year
Slightly less than 10 trillion km
The Universe is ~13.8 billion years old
The Universe

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The Universe

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The Universe

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The Universe

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Define main-sequence star.
Explain the criteria used to classify stars as giants.
Focus Questions 16.2

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Hertzsprung-Russell Diagram
Shows the relation between stellar brightness (absolute magnitude) and temperature
Diagram is made by plotting each star’s:
Luminosity (brightness) and
Temperature
Classifying Stars: H-R Diagrams

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Parts of an H-R diagram
Main-sequence stars
90% of all stars
Band through the center of the H-R diagram
Sun is in the main-sequence
Giants (or red giants)
Large and very luminous
Upper-right on the H-R diagram
Very large giants are called supergiants
Only a few percent of all stars
Classifying Stars: H-R Diagrams

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White dwarfs
Fainter than main-sequence stars
Small (approximate the size of Earth)
Lower-central area on the H-R diagram
Not all are white
Classifying Stars: H-R Diagrams

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Classifying Stars: H-R Diagrams

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List and describe the stages in the evolution of a typical Sun-like star.
Focus Question 16.3

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Stars exist because of gravity
Two opposing forces in a star are:
Gravity: contracts
Thermal nuclear energy: expands
Stages
Birth
In dark, cool, interstellar clouds (nebulae)
Gravity contracts the cloud
Temperature rises
Becomes a protostar
Stellar Evolution

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Protostar
Gravitational contraction of gasses continues
Core reaches 10 million K
Hydrogen nuclei fuse
Become helium nuclei
Process is called hydrogen fusion
Energy is released
Outward pressure balanced by gravity
Star becomes a stable main-sequence star
Stellar Evolution

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Main-sequence stage
Stars age at different rates
Massive stars
Use fuel faster
Exist for only a few million years
Small stars
Use fuel slowly
Exist for perhaps hundreds of billions of years
90% of a star’s life is in the main-sequence
Stellar Evolution

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Red giant stage
Hydrogen burning migrates outward
Star’s outer envelope expands
Surface cools
Surface becomes red
Core collapses as helium converts to carbon
Eventually all nuclear fuel is used
Gravity squeezes the star
Variable stars alternately expand and contract
Never reach equilibrium
Stellar Evolution

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Stellar Evolution

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Burnout and death
Final stage depends on mass
Low-mass star
0.5 solar mass
Red giant collapses and becomes a white dwarf
Intermediate-mass (Sun-like) star
Between 0.5 and 8 solar masses
Red giant collapses, planetary nebula forms, then becomes a white dwarf
Massive star
Over 8 solar masses
Terminates in a supernova
Interior condenses and may produce a hot, dense object that is either a neutron star or a black hole
Stellar Evolution

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Stellar Evolution

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Compare and contrast the final state of Sun-like stars to the remnants of the most massive stars.
Focus Question 16.4

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White dwarves
Small (some no larger than Earth)
Dense
Can be more massive than the Sun
Spoonful weighs several tons
Atoms take up less space
Electrons displaced inward
Called degenerate matter
Hot surface
Cools to become a black dwarf
Stellar Remnants

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Stellar Remnants

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Neutron stars
Forms from a more massive star
Star has more gravity
Squeezes itself smaller
Remnant of a supernova
Gravitational force collapses atoms
Electrons combine with protons to produce neutrons
Small size
Stellar Remnants

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Neutron stars
Pea size sample
Weighs 100 million tons
Same density as an atomic nucleus
Strong magnetic field
First one discovered in early 1970s
Pulsar (pulsating radio source)
Found in the Crab Nebula (remnant of an a.d. 1054 supernova)
Stellar Remnants

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Stellar Remnants

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Black holes
More dense than neutron stars
Intense surface gravity lets no light escape
As matter is pulled in
Becomes very hot
Emits x-rays
Cygnus X-1
First black hole to be identified
Orbits a massive supergiant companion once every 5.6 days
Accretion disk—gases spiral around a “void” while emitting a steady stream of x-rays
Stellar Remnants

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Stellar Remnants

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List the three major types of galaxies.
Explain the formation of large elliptical galaxies.
Focus Questions 16.5

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Galaxies—collections of interstellar matter, stars, and stellar remnants that are gravitationally bound
Three basic types of galaxies
Spiral galaxy
Arms extending from nucleus
Large diameter of 20,000 to 125,000 light years
Contains both young and old stars
e.g., Milky Way
Barred spiral galaxy – band of stars extending outward from central bulge merges with spiral arms
Galaxies and Galactic Clusters

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Galaxies and Galactic Clusters

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Galaxies and Galactic Clusters

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Elliptical galaxy
Ellipsoidal shape
Most are smaller than spiral galaxies; however, they are also the largest known galaxies
All small galaxies are known as dwarf galaxies
Irregular galaxy
Lacks symmetry
About 25% of all galaxies
Contains mostly young stars
For example, Magellanic Clouds
Galaxies and Galactic Clusters

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Galaxies and Galactic Clusters

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Galactic cluster
Group of galaxies
Some contain thousands of galaxies
Local Group
Our own group of galaxies
Consists of more than 40 galaxies
May contain many undiscovered dwarf galaxies
Supercluster
Huge swarm of galaxies
May be the largest entity in the universe
Galaxies and Galactic Clusters

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Galaxies and Galactic Clusters

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Galactic Collisions
Driven by one galaxy’s gravity disturbing another
A large galaxy may engulf a dwarf satellite galaxy
Two dwarf satellite galaxies are currently merging with the Milky Way
Two galaxies of similar size may pass through one another without merging
Interstellar matter will likely interact
Triggers an intense period of star formation
In 2 to 4 billion years, 50% probability that Milky Way and Andromeda Galaxies will collide and merge
Galaxies and Galactic Clusters

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Galaxies and Galactic Clusters

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37

Describe the big bang theory.
Explain what it tells us about the universe.
Focus Questions 16.6

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Big Bang Theory
Describes the birth, evolution, and fate of the universe
Universe was once confined to a “ball” that was:
Supermassive
Dense
Hot
About 13.8 billion years ago, universe began expanding rapidly in all directions
The Big Bang Theory

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Doppler effect
Change in wavelength due to motion
Movement away stretches the wavelength
Longer wavelength
Light appears redder
Movement toward “squeezes” the wavelength
Shorter wavelength
Light shifted toward the blue
The Big Bang Theory

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The Big Bang Theory

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Most galaxies exhibit a red Doppler shift (cosmological red shifts)
Far galaxies
Exhibit the greatest shift
Greater velocity
Discovered in 1929 by Edwin Hubble
Hubble’s Law
Recessional speed of galaxies is proportional to their distance
Expanding universe accounts for red shifts
The Big Bang Theory

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The Big Bang Theory

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Predictions of the Big Bang Theory
If the universe is unimaginably hot, then researchers should be able to detect the remnant of that heat
Continued expansion of the universe would stretch the waves so by now they are detectable as long-wavelength radio waves
Cosmic background radiation
Detected in 1965
The Big Bang Theory

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Fate of the universe
Two possibilities:
“Big chill”
Stars slowly burn out
Replaced by invisible degenerate matter and black holes
Travel outwards through an endless, dark, cold universe
“Big crunch”
Outward flight of galaxies slows and eventually stops
Gravitational contraction causes all matter to collide and coalesce into high-energy, high-density state, from which the universe began
The Big Bang Theory

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The Big Bang Theory

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Final fate depends on density of the universe
If density is more than the critical density, universe
will contract
If density is less than the critical density, universe will expand forever
The Big Bang Theory

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Two other constituents complicate the fate of the universe:
Dark matter
One quarter of the universe
Produces no detectable light energy
Exerts a force much like gravity
Dark energy
Exerts a force that pushes matter outward
Though to be the dominant force in behind the fate of the universe
Predicts universe will expand forever
The Big Bang Theory

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